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Study on the tribological properties of metal rolling bearing under lubrication with diketone lubricants

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Science China(Technological Sciences) 2024年第7期67卷 2003-2017页

作者： DU ShaoNan zhang ChenHui LUO zhi State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China Beijing National Laboratory of Molecular Sciences CAS Key Laboratory of Engineering PlasticsInstitute of ChemistryChinese Academy of SciencesBeijing 100190China

In this article, 1-(4-ethylphenyl)-nonane-1,3-dione(0206) was prepared by Claisen condensation. By mixing 0206, chelate, and base oil in a ratio of 3.2:4.8:2, a diketone lubricant(PAO=14(20%)) that can achieve superlubricity was prepared and applied to bearing lubrication experiments. The experimental results show that when the bearing was lubricated by base oil, the friction coefficient(COF) and temperature rise decreased with the decrease of the viscosity of PAO. When PAO=14(20%) was used as the lubricant, the COF of the bearing was the lowest(0.001), and the wear morphology was comparable to that of the bearing lubricated with commercial lubricant. Compared with the base oil with the same viscosity, it is found that the COF and temperature rise of the bearing lubricated by PAO=14(20%) were lower under any experimental conditions. And when the amount of lubricant added was 10 μL, the COF of the bearing lubricated by PAO=14(20%) reached a very low value(0.0004).Bearing ball surface analysis identified the formation of diketone adsorption films. Combined with the previous PAO=14(20%)superlubricity mechanism, it was considered that the occurrence of tribochemical reaction and the bearing effect of chelates were the main reasons for the existence of ultra-low friction coefficient and low wear. In addition, when there were polar molecules in the lubricant, they were adsorbed on the metal surface through tribochemical reactions, resulting in many irregular pits on the surface.

关键词： superlubricity diketone chelate tribochemical recations bearing lubrication

Better use of experience from other reservoirs for accurate production forecasting by learn-to-learn method

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Petroleum Science 2024年第1期21卷 716-728页

作者： Hao-Chen Wang Kai zhang Nancy Chen Wen-Sheng Zhou Chen Liu Ji-Fu Wang Li-Ming zhang zhi-gang Yu Shi-Ti Cui Mei-Chun Yang China University of Petroleum(East China) 66 Changjiang West RoadQingdao West Coast New AreaQingdao266580ShandongChina University of Calgary 2500 University Dr NWCalgaryT2N 1N4AlbertaCanada Qingdao University of Technology Qingdao266071ShandongChina State Key Laboratory of Offshore Oil Exploitation Beijing100028China CNOOC Research Institute Ltd. Beijing100028China CNPC Tarim Oilfield Branch Company Korla841000XinjiangChina National Engineering Laboratory for Exploration and Development of Low-Permeability Oil and Gas Fields Xi'an710000ShaanxiChina Sinopec Matrix Co. LTDQingdao266000ShandongChina

To assess whether a development strategy will be profitable enough,production forecasting is a crucial and difficult step in the *** development history of other reservoirs in the same class tends to be studied to make predictions ***,the permeability field,well patterns,and development regime must all be similar for two reservoirs to be considered in the same *** results in very few available experiences from other reservoirs even though there is a lot of historical information on numerous reservoirs because it is difficult to find such similar *** paper proposes a learn-to-learn method,which can better utilize a vast amount of historical data from various ***,the proposed method first learns how to learn samples before directly learning rules in ***,by utilizing gradients from networks with independent parameters and copied structure in each class of reservoirs,the proposed network obtains the optimal shared initial parameters which are regarded as transferable information across different *** on that,the network is able to predict future production indices for the target reservoir by only training with very limited samples collected from reservoirs in the same *** cases further demonstrate its superiority in accuracy to other widely-used network methods.

关键词： Production forecasting Multiple patterns Few-shot learning Transfer learning

Elevated nitrogen and co-evolution history with competitors shape the invasion process of Galinsoga quadriradiata

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Journal of Plant Ecology 2024年第4期17卷 9-22页

作者： Wen-gang zhang Xing-Jiang Song Laís Petri gang Liu Xiao-Yan Chen Rui-Ling Liu Fang-Fang Huang Jia-Bin Zou zhi-Hong Zhu College of Life Sciences Shaanxi Normal UniversityXi’an 710119China School for Environment and Sustainability University of MichiganAnn ArborMI 48109USA Research Center for UAV Remote Sensing Shaanxi Normal UniversityXi’an 710119China Changqing Teaching&Research Base of Ecology Shaanxi Normal UniversityXi’an 710119China Guangdong Provincial Key Laboratory of Silviculture Protection and UtilizationGuangdong Academy of ForestryGuangzhou 510520China

Invasive plants usually experience population differentiation as they expand from their initial invasive range to the ***,invasive plants usually encounter competitors which shared different co-evolutionary histories with *** factors may lead to varying responses of invasive plant populations to elevated nitrogen deposition during ***,this issue has received limited attention in prior *** address these challenges,we conducted a greenhouse experiment to investigate how population differentiation of Galinsoga quadriradiata interacts with the presence of various competitors in response to increased nitrogen *** types(new or old that shared short or long co-evolutionary history with the invader,respectively)were set to compete with the invasive central and edge populations under different nitrogen addition *** from the central population of ***,originating from the initial invasion range,showed greater total mass,reproduction and interspecific competitiveness compared with the edge *** addition improved growth and reproductive performance in both populations,and the central population had a stronger response compared with the edge *** performance of *** was inhibited more effectively by old competitors than new *** results indicate that population differentiation occurs in terms of growth and competitiveness during the range expansion of ***,with the central population exhibiting superior ***-evolutionary history with competitors is considered unfavorable for invasive plants in this *** results highlight the combined effects of population differentiation in invasive species and their co-evolution history with competitors in the context of global change factors.

关键词： Galinsoga quadriradiata central population edge population interspecific competition population differentiation elevated nitrogen

GABRP regulates chemokine signaling,macrophage recruitment,and tumor progression in pancreatic cancer through tuning KCNN4-mediated Ca2+ signaling

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GABRP regulates chemokine signaling,macrophage recruitment,a...

Deciphering and integrating invariants for neural operator learning with various physical mechanisms

中国生理学会张锡钧基金第十五届全国青年优秀生理学学术论文交流及评奖会议;中国生理学会第十三届全国青年生理学工作者学术会议

作者：蒋书恒 zhi-gang zhang State Key Laboratory of Oncogenes and Related Genes Shanghai Cancer InstituteRen Ji HospitalSchool of MedicineShanghai Jiao Tong University

目的:Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer-related death ***-initiated signaling pathway is profoundly implicated in tumor initiation and ***,we investigated whether dysregulated neurotransmitter receptors play a role during pancreatic tumorigenesis.方法:The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) datasets were

关键词： GABRP regulates chemokine signaling,macrophage recruitment,and tumor progression in pancreatic cancer through tuning KCNN4-mediated Ca signaling

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National Science Review 2024年第4期11卷 111-122页

作者： Rui zhang Qi Meng zhi-Ming Ma Academy of Mathematics and Systems Science Chinese Academy of Sciences(CAS) Microsoft Research

Neural operators have been explored as surrogate models for simulating physical systems to overcome the limitations of traditional partial differential equation(PDE) solvers. However, most existing operator learning methods assume that the data originate from a single physical mechanism, limiting their applicability and performance in more realistic scenarios. To this end, we propose the physical invariant attention neural operator(PIANO) to decipher and integrate the physical invariants for operator learning from the PDE series with various physical mechanisms. PIANO employs self-supervised learning to extract physical knowledge and attention mechanisms to integrate them into dynamic convolutional *** to existing techniques, PIANO can reduce the relative error by 13.6%–82.2% on PDE forecasting tasks across varying coefficients, forces or boundary conditions. Additionally, varied downstream tasks reveal that the PI embeddings deciphered by PIANO align well with the underlying invariants in the PDE systems, verifying the physical significance of PIANO.

关键词： neural operator PDE solver contrastive learning physical invariants

SNR-adaptive deep joint source-channel coding scheme for image semantic transmission with convolutional block attention module

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The Journal of China Universities of Posts and Telecommunications 2024年第1期31卷 1-11页

作者： Yang Yujia Liu Yiming zhang Wenjia zhang zhi State Key Laboratory of Networking and Switch Technology Beijing University of Posts and TelecommunicationsBeijing 100876China

With the development of deep learning(DL),joint source-channel coding(JSCC)solutions for end-to-end transmission have gained a lot of *** deep JSCC schemes support dynamically adjusting the rate according to different channel conditions during transmission,enhancing robustness in dynamic wireless ***,most of the existing adaptive JSCC schemes only consider different channel conditions,ignoring the different feature importance in the image processing and *** uniform compression of different features in the image may result in the compromise of critical image details,particularly in low signal-to-noise ratio(SNR)*** address the above issues,in this paper,a dual attention mechanism is introduced and an SNR-adaptive deep JSCC mechanism with a convolutional block attention module(CBAM)is proposed,in which matrix operations are applied to features in spatial and channel dimensions *** proposed solution concatenates the pooling feature with the SNR level and passes it sequentially through the channel attention network and spatial attention network to obtain the importance evaluation *** show that the proposed solution outperforms other baseline schemes in terms of peak SNR(PSNR)and structural similarity(SSIM),particularly in low SNR scenarios or when dealing with complex image content.

关键词： semantic communication joint source-channel coding image transmission

A Local Tb Theorem for Square Functions and Parabolic Layer Potentials

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Acta Mathematica Sinica,English Series 2024年第8期40卷 1941-1966页

作者： zhi Dan WANG Guo Ming zhang School of Physical and Mathematical Sciences Nanjing Tech UniversityNanjing 211816P.R.China Frontiers Science Center for Nonlinear Expectations Ministry of EductionResearch Center for Mathematics and Interdisciplinary SciencesShandong UniversityQingdao266237P.R.China

In this paper,we give a locally parabolic version of Tb theorem for a class of vector-valued operators with off-diagonal decay in L^(2) and certain quasi-orthogonality on a subspace of L^(2),in which the testing functions themselves are also *** an application,we establish the boundedness of layer potentials related to parabolic operators in divergence form,defined in the upper half-space Rn+2+:={(x,t,λ)∈R^(n+1)×(0,∞)},with uniformly complex elliptic,L^(∞),t,λ-independent coefficients,and satisfying the De Giorgi/Nash estimates.

关键词： Local Tb theorems Calderon-Littlewood-Paley family Parabolic layer potentials Carleson measure estimates

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柴油机燃烧模式切换过程燃烧特性变化试验

北京理工大学学报 2016年第9期36卷 910-916页

作者：柴智刚张付军北京理工大学机械与车辆学院北京100081

为研究柴油机在传统燃烧与低温燃烧的燃烧模式切换过程中,如何识别缸内当前所处的燃烧模式,以及不同喷油参数在不同的燃烧模式对燃烧特性参数的影响,在一台高压共轨柴油机1 500r·min-1、30%负荷下采用燃油单次喷射、调节EGR率方式实现... 详细信息

为研究柴油机在传统燃烧与低温燃烧的燃烧模式切换过程中,如何识别缸内当前所处的燃烧模式,以及不同喷油参数在不同的燃烧模式对燃烧特性参数的影响,在一台高压共轨柴油机1 500r·min-1、30%负荷下采用燃油单次喷射、调节EGR率方式实现燃烧模式切换并进行了试验研究.结果表明,EGR率从0增加到55%,缸内燃烧起点位置稍有后移,但变化不大,当EGR率超过45%后,缸内开始进入低温燃烧模式,瞬时放热率曲线初始上升过程,由于冷焰反应持续期增加导致出现的二阶段滞燃,可以作为识别当前的燃烧模式的特征,控制缸内燃烧模式;喷油相位从-14°CA ATDC推迟到-7°CA ATDC,对传统燃烧模式滞燃期和燃烧持续期的影响较小,但对低温燃烧的燃烧持续期影响较大,同时,当喷油相位推迟到-7°CA ATDC时,缸内接近失火;喷油压力从75MPa提高到140MPa,在传统和低温燃烧模式均可以改善发动机的油气混合程度,缸内最大爆发压力及瞬时放热率峰值增加,指示热效率有所增加,但幅度变化不大.

关键词：柴油机低温燃烧废气再循环燃烧模式

Visible-light-induced organocatalyzed C（sp2）–H bond functionalization of 1,3-azoles with trifluoroacetylsilanes

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Science China Chemistry 2024年第11期67卷 3662-3668页

作者： Zhengyu Li Zeguo zhang zhihan zhang gang Zhou Yizhi zhang Shanshan Liu Xiao Shen The Institute for Advanced Studies Engineering Research Center of Organosilicon Compounds & Materials Ministry of EducationWuhan University College of Chemistry Central China Normal University

Previous carbene insertion to C–H bonds of 1,3-azoles relied on metal carbene species. Herein, we report a metal-free C（sp2）–H bond functionalization of 1,3-azoles with trifluoroacetylsilanes. The reaction features mild conditions, broad substrate scope and wide functional group tolerance. The mechanistic study supports that the success of the reaction is probably attributed to the dual roles of trifluoroacetylsilanes under the photocatalyzed conditions: generating carbenes which undergo cyclopropanation and generating biradicals which promote ring-opening aromatization of the in situ generated fused cyclopropanes.

关键词： C(sp2)–H bond functionalization carbenes biradicals cyclopropanation brook rearrangement