检索结果-南通市图书馆

Evaluation of ambient air quality in Guangzhou, China

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2007年第4期19卷 432-437页

作者： ZHOU Kai YE You-hua LIU Qiang LIU ai-jun PENG Shao-lin South China Botanical Garden Chinese Academy of Sciences Guangzhou 510650 China. Graduate School of the Chinese Academy of Sciences Beijing 100039 China School of Life Sciences Sun Yat-sen University Guangzhou 510275 China Department of Biology Hainan Normal University Haikou 571158 China Climatic and Agrometeorological Center of Guangdong Province Guangzhou 510080 China

On the basis of the reported air quality index （API） and air pollutant monitoring data provided by the Guangzhou Environment Monitoring Stations over the last twenty-five years, the characteristics of air quality, prominent pollutants, and variation of the average annual concentrations of SOE, NOE, total suspended particulate （TSP）, fine particulates （PM10）, CO and dustfall in Guangzhou City were analyzed. Results showed that TSP was the prominent pollutant in the ambient air environment of Guangzhou City. Of the prominent pollutants, TSP accounted for nearly 62%, SOE 12.3%, and NOx 6.4%, respectively. The average API of Guangzhou over 6 years was higher than that of Beijing, Tianjin, Nanjing, Hangzhou, Suzhou and Shanghai, and lower than that of Shenzhen, Zhuhai and Shantou. Concentrations of air pollutants have shown a downward trend in recent years, but they are generally worse than ambient air quality standards for USA, Hong Kong and EU. SOE and NOx pollution were still serious, impling that waste gas pollution from all kinds of vehicles had become a significant problem for environmental protection in Guangzhou. The possible causes of worsening air quality were also discussed in this paper.

关键词： air pollution index (API) total suspended particulates (TSP) atmospheric quality Guangzhou

Clinical characteristics of patients with hepatitis and cirrhosis and the construction of a prediction model

在线全文

学校读者我要写书评

暂无评论

World Journal of Hepatology 2025年第2期17卷 54-64页

作者： Yu-Shuang Huang Wei Gao ai-jun Sun Chun-Wen Pu Shuang-Shuang Xu Department of Infectious Diseases Dalian Public Health Clinical CenterDalian 116031Liaoning ProvinceChina Department of Gastroenterology The First Affiliated Hospital of Dalian Medical UniversityDalian 116011Liaoning ProvinceChina Dalian Public Health Clinical Center Dalian Municipal Research Institute for Public HealthDalian 116031Liaoning ProvinceChina

BACKGROUND Hepatitis B-associated cirrhosis is an important disease burden in ***,there is a lack of effective predictors in clinical practice to drive delivery and enable early treatment to delay disease *** To analyzing the clinical characteristics of patients with hepatitis and cirrhosis,the nomogram model was established and *** The clinical data of 1070 patients with hepatitis B who were treated in our hospital from October 2015 to July 2022 were *** a 7:3 ratio,749 cases were divided into training cohorts and 321 cases were divided into validation *** addition,the training cohort and validation cohort were further divided into hepatitis group and hepatitis B-related cirrhosis group based on whether the patient progressed to *** logistic regression was used to analyze the influencing factors of hepatitis progression to cirrhosis.A roadmap prediction model was established,and the predictive effect of the model was evaluated by patientsubject receiver operating characteristic curve(ROC),and the effectiveness of the model was evaluated by decision curve *** Binary logistic regression analysis was performed using hepatitis B-related cirrhosis=1 and hepatitis=0 as dependent variables,and univariate analysis of serological indicators was used as *** results showed that glutamic oxaloacetate aminotransferase/glutamate acetone aminotransferase levels,prothrombin time activity,and hepatitis B e antigen levels were all contributing factors to the progression of hepatitis to *** area under the ROC curve was 0.693[95%confidence interval(CI):0.631 to 0.756]for the training cohort and 0.675(95%CI:0.561 to 0.790)for the validation *** addition,the decision analysis curves of the prediction models of both the training cohort and the validation cohort confirmed the effectiveness of the nomogram prediction *** Three independent factors influencing the progression

关键词： Hepatitis Hepatitis B-related cirrhosis Clinical features Influencing factors Nomogram

Evaluating acoustic communication performance of micro autonomous underwater vehicles in confined spaces

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Information Technology & Electronic Engineering 2018年第8期19卷 1013-1023页

作者： Qiu-yang TAO Yue-hai ZHOU Feng TONG ai-jun SONG Fumin ZHANG School of Electrical and Computer Engineering Georgia Institute of Technology College of Ocean and Earth Sciences Xiamen University Department of Electrical and Computer Engineering The University of Alabama

Micro-sized autonomous underwater vehicles(μAUVs) are well suited to various applications in confined underwater spaces. Acoustic communication is required for many application scenarios of μAUVs to enable data transmission without surfacing. This paper presents the integration of a compact acoustic communication device with a μAUV prototype. Packet reception rate(PRR) and bit error rate(BER) of the acoustic communication link are evaluated in a confined pool environment through experiments while the μAUV is either stationary or *** pinpoint several major factors that impact the communication performance. Experimental results show that the multi-path effect significantly affects the synchronization signals of the communication device. The relative motion between the vehicle and the base station also degrades the communication performance. These results suggest future methods towards improvements.

关键词： Autonomous underwater vehicles Underwater acoustic communications Confined water space

Hydrodesulfurization and Hydrodenitrogenation Kinetics of a Heavy Gas Oil over NiMo/Al_2O_3 Catalysts

在线全文

学校读者我要写书评

暂无评论

高校化学工程学报 2005年第6期19卷 762-766页

作者： DUAN ai-jun XU Chun-ming LIN Shi-xiong CHUNG Keng H State Key Laboratory of Heavy Oil Processing University of Petroleum Beijing 102249 China Syncrude Canada Ltd. 9421 - 17 Avenue Edmonton Alberta Canada T6N IH4

The kinetics of Athabasca bitumen derived heavy gas oil over NiMo/Al2O3 catalysts were studied in a JQ-II high-pressure microscale hydrotreator unit under different operation conditions, including temperature, pressure, H/O ratio and LHSV. The multi-parameter models of hydrodesulfurization and hydrodenitrogenation were proposed. The model parameters verify that the HDS and HDN reactions follow 1.5-order and 1.6-order kinetic rules, respectively. The kinetic activation energies of HDN and HDS over Com, Hom1 and Hom2 show that homemade catalysts exhibit higher activities in HDN than commercial catalyst. Using the multi-parameter kinetic model to predict the contents of sulfur and nitrogen in products is in good agreement with the experimental data.

关键词：加氢脱硫加氢脱氮动力学模型重气油 NiMo/Al2O3催化剂

Pitting Kinetics of 304 Stainless Steel Using ESPI Detection Technique

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2015年第4期28卷 430-437页

作者： Wen-Ming Tian Ying-jun ai Song-Mei Li Nan Du Chao Ye School of Materials Science and Engineering Beihang University National Defence Key Discipline Laboratory of Light Alloy Processing Science and Technology Institute Nanchang Hangkong University

The electronic speckle pattern interferometer was used to in situ monitor the pitting corrosion of 304 stainless steel at anodic polarization. The pitting current and pitting current density of a single pit were obtained. The pit growth was controlled by the corrosion products diffusion. The pit morphology was observed by a scanning electron microscope. The results showed that the pit was dish shaped, and the geometric parameters and pit growth time conformed to the function of Y = A ＋ B1t ＋ B2t2 ＋ B3t3.

关键词： Stainless steel Corrosion Electronic speckle pattern interferometry (ESPI) Pitting

Bispectrum Feature Extraction of Gearbox Faults Based on Nonnegative Tucker3 Decomposition with 3D Calculations

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2013年第6期26卷 1182-1193页

作者： WANG Haijun XU Feiyun ZHAO jun’ai JIA Minping HU Jianzhong HUANG Peng School of Mechanical Engineering Southeast University

Nonnegative Tucker3 decomposition（NTD） has attracted lots of attentions for its good performance in 3D data array analysis. However, further research is still necessary to solve the problems of overfitting and slow convergence under the anharmonic vibration circumstance occurred in the field of mechanical fault diagnosis. To decompose a large-scale tensor and extract available bispectrum feature, a method of conjugating Choi-Williams kernel function with Gauss-Newton Cartesian product based on nonnegative Tucker3 decomposition（NTD_EDF） is investigated. The complexity of the proposed method is reduced from o（nNlgn） in 3D spaces to o（RiR2nlgn） in 1D vectors due to its low rank form of the Tucker-product convolution. Meanwhile, a simultaneously updating algorithm is given to overcome the overfitting, slow convergence and low efficiency existing in the conventional one-by-one updating algorithm. Furthermore, the technique of spectral phase analysis for quadratic coupling estimation is used to explain the feature spectrum extracted from the gearbox fault data by the proposed method in detail. The simulated and experimental results show that the sparser and more inerratic feature distribution of basis images can be obtained with core tensor by the NTD EDF method compared with the one by the other methods in bispectrum feature extraction, and a legible fault expression can also be performed by power spectral density（PSD） function. Besides, the deviations of successive relative error（DSRE） of NTD_EDF achieves 81.66 dB against 15.17 dB by beta-divergences based on NTD（NTD_Beta） and the time-cost of NTD EDF is only 129.3 s, which is far less than 1 747.9 s by hierarchical alternative least square based on NTD （NTD_HALS）. The NTD_EDF method proposed not only avoids the data overfitting and improves the computation efficiency but also can be used to extract more inerratic and sparser bispectrum features of the gearbox fault.

关键词： nonnegative tucker3 decomposition Tucker-product convolution power spectrum density updating algorithm

Nucleon ~3pF_2 Superfluid Pairing Gap in Asymmetry Nuclear Matter

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2009年第6期51卷 1113-1116页

作者： MI ai-jun ZUO Wei LI Zeng-Hua Umberto Lombardo Institute of Modern Physics Chinese Academy of Sciences 730000 Lanzhou China School of Nuclear Science and Technology Lanzhou University 730000 Lanzhou China INFN-LNS and Universit di Catania Catania 1-95123 Italy

The 3 P F2 superfluidity of neutron and proton is investigated in isospin-asymmetric nuclear matter within the Brueckner-Hartree-Fock approach and the BCS theory by adopting the Argonne V14 and the Argonne V18 nucleonnucleon interactions. We find that pairing gaps in the 3PF2 channel predicted by adopting the AV14 interaction are much larger than those by the AV18 interaction. As the isospin-asymmetry increases, the neutron 3 pF2 superfluidity is found to increase rapidly, whereas the proton one turns out to decrease and may even vanish at high enough asymmetries. As a consequence, the neutron 3pF2 superfluidity is much stronger than the proton one at high asymmetries and it predominates over the proton one in dense neutron-rich matter.

关键词： 3pF2 superfluidity asymmetric nuclear matter Brueckner-Hartree-Fock approach BCS theory

Performance and mechanism of Cr(Ⅵ)removal by zero-valent iron loaded onto expanded graphite

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2018年第5期30卷 14-22页

作者： Congbin Xu Wenjie Yang Weijiang Liu Hongliang Sun Chunlei Jiao ai-jun Lin College of Chemical Engineering Beijing University of Chemical TechnologyBeijing 100029China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China Chinese Academy for Environmental Planning Beijing 100012China

Zero-valent iron（ZⅥ） was loaded on expanded graphite（EG） to produce a composite material（EG-ZⅥ） for efficient removal of hexavalent chromium（Cr（Ⅵ））. EG and EG-ZⅥ were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）,Fourier-transform infrared（FTIR） spectroscopy and Brunauer–Emmett–Teller（BET） analysis. EG-ZⅥ had a high specific surface area and contained sub-micron sized particles of zero-valent iron. Batch experiments were employed to evaluate the Cr（Ⅵ） removal performance. The results showed that the Cr（Ⅵ） removal rate was 98.80% for EG-ZⅥ,which was higher than that for both EG（10.00%） and ZⅥ（29.80%）. Furthermore, the removal rate of Cr（Ⅵ） by EG-ZⅥ showed little dependence on solution p H within a p H range of 1–*** at pH 11, a Cr（Ⅵ） removal rate of 62.44% was obtained after reaction for 1 hr. EG-ZⅥ could enhance the removal of Cr（Ⅵ） via chemical reduction and physical adsorption,respectively. X-ray photoelectron spectroscopy（XPS） was used to analyze the mechanisms of Cr（Ⅵ） removal, which indicated that the ZⅥ loaded on the surface was oxidized, and the removed Cr（Ⅵ） was immobilized via the formation of Cr（III） hydroxide and Cr（III）–Fe（III）hydroxide/oxyhydroxide on the surface of EG-ZⅥ.

关键词： Zero-valent iron(ZVI) Expanded graphite(EG) Cr(Ⅵ) removalMechanism

Amorphous 3D pomegranate-like NiCoFe nanoassemblies derived by bi-component cyanogel reduction for outstanding oxygen evolution reaction

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2021年第2期30卷 260-267,I0009页

作者： Zi-Juan Wang Mi-Xue Jin Lu Zhang ai-jun Wang Jiu-Ju Feng Key Laboratory of the Ministry of Education for Advanced Catalysis Materials College of Chemistry and Life SciencesCollege of Geography and Environmental SciencesZhejiang Normal UniversityJinhua 321004ZhejiangChina

As a representative type of self-supported templates, cyano-bridged cyanogels provide ideal plateaus for synthesis of three-dimensional(3 D) nanostructures. Herein, 3 D pomegranate-like Fe-doped NiCo nanoassemblies(3 D PG-NiCoFe NAs) were synthesized via facile one-step bi-component cyanogel reduction with NaBH_4 as the reducing agent. Specifically, the influence of the incorporated Fe amount was carefully investigated by finely adjusting the feeding molar ratios of the Ni/Co/Fe atoms in the *** virtue of the unique structure and enriched oxygen vacancies originated from well-modulated electronic structures, the 3 D PG-NiCoFe-211 NAs exhibited outstanding electrocatalytic performances for oxygen evolution reaction(OER) in alkaline solution, outperforming commercial RuO_2 catalyst. The current incorporation of foreign metal atom into host material provides some valuable insights into design and synthesis of metal-based nanocatalysts for constructing practical water splitting devices.

关键词： Transition-metal-based nanocatalysts Cyanogel Three-dimensional pomegranate-like nanoassemblies Oxygen vacancy Oxygen evolution reaction