检索结果-南通市图书馆

A synthesis of the Cretaceous wildfire record related to atmospheric oxygen levels?

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Palaeogeography 2024年第1期13卷 149-164页

作者： Da-Wei Lü Wen-Xu Du Zhi-Hui Zhang Yuan Gao tian-tian wang Jin-cheng Xu Ao-Cong Zhang cheng-Shan wang Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals College of Earth Sciences and EngineeringShandong University of Science and TechnologyQingdao 266590Shandong ProvinceChina School of Earth Sciences and Resources China University of GeosciencesBejing 100083China Institute of Earth Sciences China University of Geosciences(Bejing)Beijing 100083China

The Cretaceous was a significant greenhouse period in Earth's history with higher atmospheric CO_(2) levels and temperatures than today. Although evidence of combustion has been widely described from the Cretaceous deposits, our understanding of the spatiotemporal diversification pattern and process of the Cretaceous wildfires is still limited. In this study, we comprehensively synthesize a total of 271 published Cretaceous wildfire occurrences based on the by-products of burning, including fossil charcoal, pyrogenic inertinite(fossil charcoal in coal), and pyrogenic polycyclic aromatic hydrocarbons(PAHs). Spatially, the dataset shows a distinctive distribution of reported wildfire evidence characterized by high concentration in the middle latitudinal areas of the Northern Hemisphere(30°N-60°N) over the Cretaceous. Temporally, an overall increasing trend of the reported wildfire data from the Early Cretaceous to the Late Cretaceous is coincident with higher atmospheric O_(2) levels. However, the spatial and temporal patterns may result from many types of factors, such as taphonomy, preservation, and researcher biases, instead of a real picture of the Cretaceous wildfire evolution. To better understand the spatiotemporal diversification of the Cretaceous wildfire, more investigations on the record of wildfire occurrences during this period would be necessary in the future.

关键词： Wildfire Cretaceous Atmospheric oxygen Taphonomy Charcoal

Small-diameter acellular porcine corneal stroma for peripheral corneal ulceration treatment

在线全文

学校读者我要写书评

暂无评论

International Journal of Ophthalmology(English edition) 2024年第5期17卷 831-837页

作者： tian Liang Xia wang Jie Wu Yan cheng Department of Ophthalmology Xi’an No.1 HospitalXi’an 710002Shaanxi ProvinceChina

AIM:To evaluate the clinical efficacy of small-diameter acellular porcine corneal stroma(SAPS)for the treatment of peripheral corneal ulceration(PCU).METHODS:This retrospective clinical study included 18 patients(18 eyes)with PCU between April 2018 and December *** patients had PCU and underwent lamellar keratoplasty with *** indicators included preoperative and postoperative best-corrected visual acuity(BCVA)and transparency of *** infection control rate in the surgical eye-lesion area was also ***:Eighteen patients underwent lamellar keratoplasty with SAPS to treat *** of the patients experienced rejection after 6mo(18/18)and 12mo(16/16)of *** BCVA(0.47±0.30)at the 6mo followup after operation was significantly improved compared with the baseline(0.99±0.80),and the difference was statistically significant(Z=-3.415,P<0.05).The BCVA at the 12mo follow-up after operation was not statistically significant compared to the 6mo(Z=0,P=1).With time,the SAPS graft gradually became *** the 6mo(18/18)and 12mo(16/16)follow-up,none of the patients had recurrent corneal ***:SAPS is clinically effective in the treatment of PCU,improving the patient’s BCVA and reducing the incidence of rejection after keratoplasty.

关键词： acellular porcine corneal stroma lamellar keratoplasty infectious corneal ulcer

CO_(2)flooding in shale oil reservoir with radial borehole fracturing for CO_(2)storage and enhanced oil recovery

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Petroleum Science 2024年第1期21卷 519-534页

作者： Jia-cheng Dai tian-Yu wang Jin-Tao Weng Kang-Jian tian Li-Ying Zhu Gen-Sheng Li State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing102249China China National Oil and Gas Exploration and Development Company Limited Beijing100034China

This study introduces a novel method integrating CO_(2)flooding with radial borehole fracturing for enhanced oil recovery and CO_(2)underground storage,a solution to the limited vertical stimulation reservoir volume in horizontal well fracturing.A numerical model is established to investigate the production rate,reservoir pressure field,and CO_(2)saturation distribution corresponding to changing time of CO_(2)flooding with radial borehole fracturing.A sensitivity analysis on the influence of CO_(2)injection location,layer spacing,pressure difference,borehole number,and hydraulic fractures on oil production and CO_(2)storage is *** CO_(2)flooding process is divided into four *** in layer spacing will significantly improve oil production rate and gas storage ***,serious gas channeling can occur when the spacing is lower than 20 *** the pressure difference between the producer and injector,the borehole number,the hydraulic fracture height,and the fracture width can also increase the oil production rate and gas storage *** analysis shows that layer spacing and fracture height greatly influence gas storage and oil *** outcomes are expected to provide a theoretical basis for the efficient development of shale oil reservoirs in the vertical direction.

关键词： Shale oil Radial borehole fracturing Embedded discrete fracture model Enhanced oil recovery Carbon storage

How to interpret low human chorionic gonadotropin levels in cerebrospinal fluid of patients with intracranial germinoma？

在线全文

学校读者我要写书评

暂无评论

Chinese Medical Journal 2013年第24期126卷 4809-4810页

作者： CONG Lu tian cheng-lin wang Xiang-qing DONG Zhao ZHANG Jia-tang YU Sheng-yuan Department of Neurology Chinese People's Liberation Anny General Hospital Beijing 100853 China

Human chorionic gonadotropin （hCG） level in cerebrospinal fluid （CSF hCG） is very useful for thediagnosis of intracranial germinoma. We have previously reported on two patients with germinoma located in the basal ganglia. Their CSF hCG levels were extremely low upon presentation.1 However, significantly increased CSF hCG levels were detected when these two patients had a relapse. The experience acquired in these two cases is helpful to appropriately interpret the CSF hCG levels that are used to detect intracranial germinoma, evaluate the effectiveness of treatment and monitor recurrence.

关键词： germinoma, human chorionic gonadotropin cerebrospinal fluid

A Hybrid Approach for Predicting the Remaining Useful Life of Bearings Based on the RReliefF Algorithm and Extreme Learning Machine

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2024年第8期140卷 1405-1427页

作者： Sen-Hui wang Xi Kang cheng wang tian-Bing Ma Xiang He Ke Yang School of Mechatronics Engineering Anhui University of Science and TechnologyHuainan232001China Institute of Energy Hefei Comprehensive National Science CenterHefei230031China

Accurately predicting the remaining useful life(RUL)of bearings in mining rotating equipment is vital for mining *** research aims to distinguish the features associated with the RUL of bearings and propose a prediction model based on these selected *** study proposes a hybrid predictive model to assess the RUL of rolling element *** proposed model begins with the pre-processing of bearing vibration signals to reconstruct sixty time-domain *** hybrid model selects relevant features from the sixty time-domain features of the vibration signal by adopting the RReliefF feature selection ***,the extreme learning machine(ELM)approach is applied to develop a predictive model of RUL based on the optimal *** model is trained by optimizing its parameters via the grid search *** training datasets are adjusted to make them most suitable for the regression model using the cross-validation *** proposed hybrid model is analyzed and validated using the vibration data taken from the public XJTU-SY rolling element-bearing *** comparison is constructed with other traditional *** experimental test results demonstrated that the proposed approach can predict the RUL of bearings with a reliable degree of accuracy.

关键词： Bearing degradation remaining useful life estimation RReliefF feature selection extreme learning machine

The effects of various factors on spontaneous imbibition in tight oil reservoirs

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Petroleum Science 2024年第1期21卷 315-326页

作者： cheng Liu tian-Ru wang Qing You Yue-Chun Du Guang Zhao Cai-Li Dai School of Energy Resources China University of GeosciencesBeijing100083PR China School of Petroleum Engineering China University of PetroleumQingdao266580ShandongPR China

Slickwater fracturing fluids have gained widespread application in the development of tight oil reservoirs. After the fracturing process, the active components present in slickwater can directly induce spontaneous imbibition within the reservoir. Several variables influence the eventual recovery rate within this procedure, including slickwater composition, formation temperature, degree of reservoir fracture development, and the reservoir characteristics. Nonetheless, the underlying mechanisms governing these influences remain relatively understudied. In this investigation, using the Chang-7 block of the Changqing Oilfield as the study site, we employ EM-30 slickwater fracturing fluid to explore the effects of the drag-reducing agent concentration, imbibition temperature, core permeability, and core fracture development on spontaneous imbibition. An elevated drag-reducing agent concentration is observed to diminish the degree of medium and small pore utilization. Furthermore, higher temperatures and an augmented permeability enhance the fluid flow properties, thereby contributing to an increased utilization rate across all pore sizes. Reduced fracture development results in a lower fluid utilization across diverse pore types. This study deepens our understanding of the pivotal factors affecting spontaneous imbibition in tight reservoirs following fracturing. The findings act as theoretical, technical, and scientific foundations for optimizing fracturing strategies in tight oil reservoir transformations.

关键词： Tight oil reservoir Spontaneous imbibition Nuclear magnetic resonance Slickwater fracturing fluid Fluid utilization degree

Unveiling evapotranspiration patterns and energy balance in a subalpine forest of the Qinghai-Tibet Plateau:observations and analysis from an eddy covariance system

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2024年第3期35卷 175-188页

作者： Niu Zhu Jinniu wang Dongliang Luo Xufeng wang cheng Shen Ning Wu Ning Zhang Binghui tian Aihong Gai chengdu Institute of Biology Chinese Academy of SciencesChengdu 610041People's Republic of China College of Resources and Environmental Sciences Gansu Agricultural UniversityLanzhou 730070People's Republic of China Mangkang Ecological Monitoring Station Tibet Ecological Security Barrier Ecological Monitoring NetworkQamdo 854500People's Republic of China Northwest Institute of Eco Environmental Resources Chinese Academy of SciencesLanzhou 730000People's Republic of China

Evapotranspiration is an important parameter used to characterize the water cycle of *** under-stand the properties of the evapotranspiration and energy balance of a subalpine forest in the southeastern Qinghai-Tibet Plateau,an open-path eddy covariance system was set up to monitor the forest from November 2020 to October 2021 in a core area of the Three Parallel Rivers in the Qing-hai-Tibet *** results show that the evapotranspira-tion peaked daily,the maximum occurring between 11:00 and 15:*** factors had significant effects on evapotranspiration,among them,net radiation the greatest(R^(2)=0.487),and relative humidity the least(R^(2)=0.001).The energy flux varied considerably in different seasons and sensible heat flux accounted for the main part of turbulent *** energy balance ratio in the dormant season was less than that in the growing season,and there is an energy imbalance at the site on an annual time scale.

关键词： Evapotranspiration Energy balance Subalpine forest Three Parallel Rivers region Southeast Qinghai-Tibet Plateau

Multi-distortion suppression for neutron radiographic images based on generative adversarial network

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第4期35卷 176-188页

作者： cheng-Bo Meng wang-Wei Zhu Zhen Zhang Zi-Tong wang Chen-Yi Zhao Shuang Qiao tian Zhang School of Physics Northeast Normal UniversityChangchun 130024China

Neutron radiography is a crucial nondestructive testing technology widely used in the aerospace,military,and nuclear ***,because of the physical limitations of neutron sources and collimators,the resulting neutron radiographic images inevitably exhibit multiple distortions,including noise,geometric unsharpness,and white ***,these distortions are particularly significant in compact neutron radiography systems with low neutron ***,in this study,we devised a multi-distortion suppression network that employs a modified generative adversarial network to improve the quality of degraded neutron radiographic *** neutron radiographic image datasets with various types and levels of distortion were built for the first time as multi-distortion suppression ***,the coordinate attention mechanism was incorporated into the backbone network to augment the capability of the proposed network to learn the abstract relationship between ideally clear and degraded *** experiments were performed;the results show that the proposed method can effectively suppress multiple distortions in real neutron radiographic images and achieve state-of-theart perceptual visual quality,thus demonstrating its application potential in neutron radiography.

关键词： Neutron radiography Multi-distortion suppression Generative adversarial network Coordinate attention mechanism

Model-driven path planning for robotic plasma cutting of branch pipe with single Y-groove based on pipe-rotating scheme

在线全文

学校读者我要写书评

暂无评论

Advances in Manufacturing 2024年第1期12卷 94-107页

作者： Yan Liu Qiu Tang Xin-cheng tian School of Control Science and Engineering Shandong UniversityJinan250061People’s Republic of China Engineering Research Center of Intelligent Unmanned System Ministry of EducationJinan250061People’s Republic of China School of Mechanical and Electronic Engineering Shandong Jianzhu UniversityJinan250101People’s Republic of China

The automatic cutting of intersecting pipes is a challenging task in *** improved automation and accuracy,this paper proposes a model-driven path planning approach for the robotic plasma cutting of a branch pipe with a single ***,it summarizes the intersection forms and introduces a dual-pipe intersection *** on this model,the moving three-plane structure(a description unit of the geometric characteristics of the intersecting curve)is constructed,and a geometric model of the branch pipe with a single Y-groove is ***,a novel mathematical model for plasma radius and taper compensation is ***,the compensation model and groove model are integrated by establishing movable ***,to prevent collisions between the plasma torch and workpiece,the torch height is planned and a branch pipe-rotating scheme is *** the established models and moving frames,the planned path description of cutting robot is provided in this novel *** accuracy of the proposed method is verified by simulations and robotic cutting experiments.

关键词： Automatic groove cutting of intersecting pipes Model-driven robot path planning Plasma beam radius and taper compensation