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Probabilistic time series forecasting with deep non-linear state space models

CAAI Transactions on Intelligence Technology 2023年第1期8卷 3-13页

作者： Heming du Shouguo du wen Li School of Computer Science College of Engineering and Computer ScienceAustralian National UniversityCanberraAustralian Capital TerritoryAustralia Shanghai Municipal Big Data Center ShanghaiChina Department of Economic Statistics School of Statistics and InformationShanghai University of International Business and EconomicsShanghaiChina

Probabilistic time series forecasting aims at estimating future probabilistic distributions based on given time series observations.It is a widespread challenge in various tasks,such as risk management and decision making.To investigate temporal patterns in time series data and predict subsequent probabilities,the state space model(SSM)provides a general framework.Variants of SSM achieve considerable success in many fields,such as engineering and statistics.However,since underlying processes in real-world scenarios are usually unknown and complicated,actual time series observations are always irregular and noisy.Therefore,it is very difficult to determinate an SSM for classical statistical approaches.In this paper,a general time series forecasting framework,called Deep Nonlinear State Space Model(DNLSSM),is proposed to predict the probabilistic distribution based on estimated underlying unknown processes from historical time series data.We fuse deep neural networks and statistical methods to iteratively estimate states and network parameters and thus exploit intricate temporal patterns of time series data.In particular,the unscented Kalman filter(UKF)is adopted to calculate marginal likelihoods and update distributions recursively for non-linear functions.After that,a non-linear Joseph form covariance update is developed to ensure that calculated covariance matrices in UKF updates are symmetric and positive definitive.Therefore,the authors enhance the tolerance of UKF to round-off errors and manage to combine UKF and deep neural networks.In this manner,the DNLSSM effectively models non-linear correlations between observed time series data and underlying dynamic processes.Experiments in both synthetic and real-world datasets demonstrate that the DNLSSM consistently improves the accuracy of probability forecasts compared to the baseline methods.

关键词： Artificial Intelligence machine learning time series

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Gear walk instability caused by brake-disc friction characteristics

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Chinese Journal of Aeronautics 2024年第2期37卷 343-359页

作者： Xiaoqiong du Bin LI wen CAI Linyin LUO School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Department of Mechanical Engineering University of MichiganAnn Arbor 48109USA AVIC General Huanan Aircraft Industry Co.Ltd. Zhuhai 519040China

A multi-body dynamic rigid-flexible coupling model of landing gear is established to study the gear walk instability caused by the friction characteristics of the brake disc.After validating the model with the experimental results,the influence of the landing gear structure and braking system parameters on gear walk is further investigated.Among the above factors,the slope of the graph for the friction coefficient of the brake disc and the relative velocity of brake stators and rotors is the most influential factor on gear walk instability.Phase trajectory analysis verifies that gear walk occurs when the coupling of multiple factors causes the system to exhibit an equivalent negative damping trend.To consider a more realistic braking case,a back propagation neural network method is employed to describe the nonlinear behavior of the friction coefficient of the brake disc.With the realistic nonlinear model of the friction coefficient,the maximum error in predicting the braking torque is less than 10%and the effect of the brake disc temperature on gear walk is performed.The results reveal that a more negative friction slope may contribute to a more severe unstable gear walk,and reducing the braking pressure is an effective approach to avoid gear walk,which provides help for future braking system design.

关键词： Gear walk Friction characteristics of brake disc Brake-induced vibration Negative damping Rigid-flexible coupling Negative slope of braking torque

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Strategic Digital Transformation of State-owned Enterprises:Mission Embedding and Mode Selection-A Case Study Based on the Typical Digital Transformation of Three State-owned Enterprises

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Frontiers of Business Research in China 2023年第1期17卷 74-125页

作者： QI Yudong du Bo wen Xin Business School Beijing Normal UniversityBeijing 100875China School of Government Beijing Normal University SchoolBeijing 100875China

China’s state-owned enterprises(SOEs)are facing an embedded integration of new functional mission,new classification reform and new digital development.These new tasks require SOEs to embrace digital strategic transformation and innovation for high-quality fulfillment of their national mission.Studying their digital transformation practices,this paper systematically explores the mechanism and path of embedding national mission into SOE digital transformation,and the mode selection of SOE digital transformation under different mission guidance.The findings are:(1)The SOE functional mission focusing on economic development,strategic support and public services in the new era is undertaken by for-profit,strategic and public functional SOEs;(2)the foreign circulation path based on the positioning mechanism-mapping mechanism and the internal consumption connection path for the state capital strategic positioning constitute a double twoway mechanism of embedding the national mission to the SOE digital strategic transformation,leading SOEs to build market-oriented,capacity-oriented and public-oriented digital transformation modes;(3)the three types of reform modes have respectively produced the action mechanism featuring agile strengthening,toughness strengthening and adaptability strengthening,which support the SOE classification performance.This paper attempts to make up for the research gap such as the lack of integration of the SOE digital strategic transformation mode by constructing the theoretical mode of SOE digital strategic transformation under the guidance of national mission,and reveals the intermediary mechanism of digital strategic transformation to support SOEs for fulfilling their functional missions.

关键词： national mission state-owned enterprises(SOEs) functional classification two-way embedding digital strategic transformation

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Trichoderma metabolites trigger aggregation behavior in Formosan subterranean termites (Coptotermes formosanus)

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Insect Science 2023年第6期30卷 1759-1772页

作者： Lang Zhang Cong Yi Chengju du Chao wen Zhiqiang Li Yong Chen Xiujun wen Cai Wang College of Forestry and Landscape Architecture South China Agricultural UniversityGuangzhouChina School of Grassland Science Beijing Forestry UniversityBeijingChina Guangdong Key Laboratory of Animal Conservation and Resource Utilization Guangdong Public Laboratory of Wild Animal Conservation and UtilizationInstitute of ZoologyGuangdong Academy of SciencesGuangzhouChina

Our previous studies have shown that some Trichoderma fungi trigger aggregation behavior in Formosan subterranean termites,Coptotermes formosanus Shiraki.However,the mechanisms underlying the induction of termite aggregation by Trichoderma fungi remain unclear.Here,we found that the aqueous or acetone extract of Trichoderma asperellum Samuels,Lieckfeldt&Nirenberg and Trichoderma virens Pers.ex Fries isolated from the gut or cuticle of C.formosanus elicited significant termite aggregation in 2-choice tests.We then screened 9 Trichoderma metabolites(3-acetoxy-2-butanone,phenol,3-ethoxypropionic acid,ethyl 2,4-dioxovalerate,diglycolic acid,d-valine,styrene,3-aminopyridine,and hexyl acetoacetate)that triggered termite aggregation.Among them,phenol(1000μg/mL),3-ethoxypropionic acid(10μg/mL),ethyl 2,4-dioxovalerate(1000μg/mL),and diglycolic acid(1000μg/mL)showed the strongest activities,triggering termite aggregation throughout the 24-h period.As T.asperellum and T.virens produce different metabolites that trigger aggregation behavior in termites,the mechanisms underlying the interaction between subterranean termites and Trichoderma fungi likely vary.Future studies are needed to test whether these chemicals can attract termites and increase bait consumption.

关键词： aggregation behavior insect-fungus interaction semiochemical subter-ranean termite Trichoderma

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Evolution of γ' precipitates in GH4742 superalloy based on complete forging-heat treatment process

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Journal of Iron and Steel Research(International) 2022年第11期29卷 1873-1885页

作者： Qiang Tian He-yong Qin wen-yun Zhang wen-wen Zhang Hai-zhu Li Qiang du Xin-gang Liu High Temperature Materials Research Division Central Iron and Steel Research InstituteBeijing 100081China College of Mechanical Engineering Yanshan UniversityQinhuangdao 066004HebeiChina

The temperature changes at the rim,1/2 radius,and bore of the turbine disk during the solution treatment were measured.Based on the measured temperature data,solution treatment experiments with different cooling rates(14,51,and 93℃/min)were performed,and the solution temperatures were 1120 and 1080℃.At all three cooling rates,the multimodal size distribution of γ' precipitates was detected,and the size of γ' precipitates is inversely related to the cooling rate.Only the secondary and tertiary γ' precipitates were found at a solution temperature of 1120℃,and the secondary γ' precipitates progressed from spherical(93 and 51℃/min)to flower-like(14℃/min)shape,with the flower-like γ' precipitates regulated by aggregation.At a solution temperature of 1080℃,the γ' precipitates evolve from cuboids(93 and 51℃/min)to irregular shapes(14℃/min).Irregular γ' precipitates are affected by the lattice mismatch between the matrix and the γ' precipitates.

关键词： GH4742 superalloy γ'precipitate Solution cooling rate Aggregation Diffusion neck

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MicroRNAs通过调节自噬影响乳腺癌的耐药性

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2020年第9期21卷 690-702页

作者： Nan wen Qing LV Zheng-gui du Department of Breast Surgery West China HospitalSichuan UniversityChengdu 610041China

自噬是一种保守的分解代谢过程,其特征在于通过溶酶体依赖性途径降解和再循环胞质成分或细胞器。它与乳腺癌的耐药性有着复杂而密切的关系。小分子核糖核酸(micro RNA,mi RNA)是小的非编码分子,可通过基因表达的转录后调控来影响众多细... 详细信息

自噬是一种保守的分解代谢过程,其特征在于通过溶酶体依赖性途径降解和再循环胞质成分或细胞器。它与乳腺癌的耐药性有着复杂而密切的关系。小分子核糖核酸(micro RNA,mi RNA)是小的非编码分子,可通过基因表达的转录后调控来影响众多细胞过程,包括自噬。许多蛋白质和途径能调节自噬,而其中一些反过来又被mi RNA调节。另外,这些mi RNA可能会影响乳腺癌的耐药性。耐药性是乳腺癌患者远处复发、转移和死亡的主要原因。在这篇综述中,我们总结了乳腺癌自噬与药物耐药性之间的因果关系,同时还讨论了自噬相关蛋白和途径及其相关的mi RNA在乳腺癌耐药性中的作用。

关键词：自噬小分子核糖核酸(microRNA) 乳腺癌耐药

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多缸柴油机冷却水腔流动不均匀性的仿真研究

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北京理工大学学报 2018年第5期38卷 476-480页

作者：杜巍包文华刘福水北京理工大学机械与车辆学院北京100081

以多缸柴油机的冷却水腔为研究对象,使用Fluent软件对直列3、4、5、6缸柴油机冷却系统的流场进行仿真.结果表明:对于冷却水套进出水口在曲轴同一端的直列柴油机,从距离入口最近的缸到远离入口的最后一缸,各缸水套间通道压力逐渐降低,各... 详细信息

以多缸柴油机的冷却水腔为研究对象,使用Fluent软件对直列3、4、5、6缸柴油机冷却系统的流场进行仿真.结果表明:对于冷却水套进出水口在曲轴同一端的直列柴油机,从距离入口最近的缸到远离入口的最后一缸,各缸水套间通道压力逐渐降低,各缸缸盖进口和出口压力逐渐增加,各缸缸盖的流量逐渐降低.在相同入口流量条件下,随着发动机气缸数增加,总进口和总出口的压差逐渐降低,整个冷却水套的流动阻力减小,各缸缸盖进出口压差的平均值逐渐减小,发动机各缸盖中最大流量和最小流量之间的差值增加,发动机各缸缸盖流量的不均匀度大幅度增加.

关键词：多缸柴油机冷却水腔流动不均匀性

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Glutamine supplementation attenuates intestinal apoptosis by inducing heat shock protein 70 in heatstroke rats

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世界急诊医学杂志(英文) 2023年第1期14卷 37-43页

作者： Li-wen du Bao-qing Xu Kai Xun Fang-qi Zhang Department of Emergency Ningbo No.2 HospitalNingbo 315000China Department of Pathology the 900th Hospital of Joint Logistics Support Force of Chinese PLAFuzhou 350025China Department of Pulmonary and Critical Care Medicine the 987th Hospital of Joint Logistics Support Force of Chinese PLABaoji 721000China

BACKGROUND:Heatstroke is the most hazardous heat-related illness and has a high fatality rate.We investigated whether glutamine supplementation could have a protective effect on heatstroke rats.METHODS:Twenty-five 12-week-old male Wistar rats(weight 305±16 g)were randomly divided into a control group(n=5),heatstroke(HS)group(n=10),and heatstroke+glutamine(HSG)group(n=10).Seven days before heat exposure,glutamine(0.4 g/[kg·d])was administered to the rats in the HSG group by gavage every day.Three hours after heat exposure,serum samples were collected to detect white blood cells,coagulation indicators,blood biochemical indicators,and inflammatory cytokines in the rats.The small intestine tissue was stained to analyze pathological structural changes and apoptosis.Finally,immunohistochemistry and Western blotting were used to analyze the expression levels of heat shock protein 70(HSP70).Multiple comparisons were analyzed by using one-way analysis of variance,and the Bonferroni test was conducted for the post hoc comparisons.RESULTS:After heat exposure,the core temperature of the HS group(40.65±0.31°C)was higher than the criterion of heatstroke,whereas the core temperature of the HSG group(39.45±0.14°C)was lower than the criterion.Glutamine supplementation restored the increased white blood cells,coagulation indicators,blood biochemical indicators,and inflammatory cytokines that were induced by heatstroke to normal levels.The intestinal mucosa was injured,and the structure of tight junctions was damaged in the HS group;however,the structure of intestinal mucosal epithelial cells was stable in the HSG group.Glutamine supplementation alleviated intestinal apoptosis and up-regulated HSP70 expression.CONCLUSION:Glutamine supplementation may alleviate intestinal apoptosis by inducing the expression of HSP70 and have a protective effect on heatstroke rats.

关键词： Heatstroke Glutamine Core temperature Intestinal apoptosis Heat shock protein 70

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Multiple Bifurcations of Critical Period for a Quartic Kolmogorov Model

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Acta Mathematicae Applicatae Sinica 2021年第4期37卷 673-681页

作者： Chao-xiong du wen-tao HUANG School of Mathematics Changsha Normal UniversityChangsha410100China School of Mathematics and Statistics Guangxi Normal UniversityGuilin541001China

Our work is concerned with the bifurcation of critical period for a quartic Kolmogorov system.By computing the periodic constants carefully,we show that point(1,1)can be a weak center of fourth order,and the weak centers condition is given.Moreover,point(1,1)can bifurcate 4 critical periods under a certain condition.In terms of multiple bifurcation of critical periodic problem for Kolmogorov model,studied results are less seen,our work is good and interesting.

关键词： singular values weak center periodic constants bifurcation of critical period

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Changes and significance of serum troponin in trauma patients: A retrospective study in a level I trauma center

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World Journal of Emergency Medicine 2022年第1期13卷 27-31页

作者： Li-wen Dou Zhe du Ji-hong Zhu Tian-bing Wang Emergency Department Peking University People’s HospitalBeijing 100044China Trauma Center Peking University People’s HospitalBeijing 100044China

BACKGROUND: Elevated troponin I(TnI) is common among trauma patients. TnI is an indicator of myocardial injury, but clinical diagnosis of blunt cardiac injury cannot be based solely on an increase in TnI. Therefore, this study aims to explore the changes and clinical significance of serum TnI in trauma patients. METHODS: The clinical data of consecutive trauma patients admitted to our trauma center between July 1, 2017 and July 31, 2020 were retrospectively analyzed. According to TnI levels within 24 hours of admission, patients were divided into the elevated and normal TnI groups. According to the TnI levels after 7 days of admission, a graph depicting a change in trend was drawn and then analyzed whether TnI was related to in-hospital mortality. RESULTS: A total of 166 patients(69 and 97 cases with elevated and normal TnI, respectively) were included in this study. The average hospital stay, intensive care time, mechanical ventilation time, and in-hospital mortality were higher in the elevated TnI group than in the normal TnI group(Pdually increased after admission and peaked at 48 hours(7.804±1.537 ng/mL). Subsequently, it decreased, and then recovered to normal within 7 days. However, 13 patients did not recover. Logistic regression analysis revealed that abnormal TnI at 7 days was independently related to in-hospital mortality. CONCLUSIONS: Trauma patients with elevated TnI levels may have a worse prognosis. Monitoring the changes in serum TnI is important, which can reflect the prognosis better than the TnI measured immediately after admission.

关键词： Trauma Blunt cardiac injury Troponin I Electrocardiography

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