检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

薄壁锥面衬套关键工艺研究

航空精密制造技术 2024年第1期60卷 65-67页

作者：孙莉洁刘勇中国航发西安动力控制科技有限公司西安710077

针对薄壁锥面衬套出现的外圆变形无法保证尺寸、改进工艺流程后定位装夹困难等问题,通过零件结构分析,优化了工艺流程,改进工装,试验磨削工艺参数,解决了薄壁锥面衬套的加工问题。

关键词：薄壁锥面衬套变形工艺流程工装参数

Sttudy on intelligent spatial decision support system of agriculture

在线全文

学校读者我要写书评

暂无评论

哈尔滨工程大学学报 2006年第B07期27卷 607-611页

作者： ZHANG Rong-mei sun jie-li Information Technology College Hebei University of Economics And Trades Shijiazhuang 050061 China

This paper studies how to apply GIS, ES, and Data mining and WEB technologies in agriculture Decision Support System, with the researching background of Hebei expert system for farming soil variable rate fertilization. A model of agriculture intelligent spatial decision support system is built and the key technologies to implement this system are described in details.

关键词：农业地理信息系统专家系统智能决策支持系统

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

深盲孔内花键插齿加工技术研究

航空精密制造技术 2024年第4期60卷 59-61页

作者：许利利岳剑龙孙莉洁陈宏涛中国航发西安动力控制科技有限公司西安710077

针对小模数深盲孔内花键插齿加工过程中产生的加工质量、效率较低的问题,对插齿刀具结构及参数进行研究分析,同时进行切削试验,得到了在数控精密插齿机上加工深盲孔内花键较适合的参数以及更优的刀具参数。通过对深盲孔内花键插齿加工... 详细信息

针对小模数深盲孔内花键插齿加工过程中产生的加工质量、效率较低的问题,对插齿刀具结构及参数进行研究分析,同时进行切削试验,得到了在数控精密插齿机上加工深盲孔内花键较适合的参数以及更优的刀具参数。通过对深盲孔内花键插齿加工技术的研究,解决了加工过程中的让刀问题,干涉也随之减少,切削力降低,工件残余热降低,工件的热变形小,提高了工件加工质量及效率。

关键词：深盲孔小模数内花键锥度热变形插齿刀参数

A strip thickness prediction method of hot rolling based on D_S information reconstruction

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2015年第6期22卷 2192-2200页

作者：孙丽杰邵诚张利 Institute of Advanced Control Technology Dalian University of Technology School of Information liaoning University

To improve prediction accuracy of strip thickness in hot rolling, a kind of Dempster/Shafer(D_S) information reconstitution prediction method(DSIRPM) was presented. DSIRPM basically consisted of three steps to implement the prediction of strip thickness. Firstly, iba Analyzer was employed to analyze the periodicity of hot rolling and find three sensitive parameters to strip thickness, which were used to undertake polynomial curve fitting prediction based on least square respectively, and preliminary prediction results were obtained. Then, D_S evidence theory was used to reconstruct the prediction results under different parameters, in which basic probability assignment(BPA) was the key and the proposed contribution rate calculated using grey relational degree was regarded as BPA, which realizes BPA selection objectively. Finally, from this distribution, future strip thickness trend was inferred. Experimental results clearly show the improved prediction accuracy and stability compared with other prediction models, such as GM(1,1) and the weighted average prediction model.

关键词： grey relational degree GM(1,1) model Dempster/Shafer (D_S) method least square method thickness prediction

Hydrogen generation from NaBH_(4) for portable proton exchange membrane fuel cell

在线全文

学校读者我要写书评

暂无评论

Materials Reports(Energy) 2024年第1期4卷 69-78页

作者： Bingxue sun Xingguo li jie Zheng Beijing National Laboratory for Molecular Sciences(BNLMS) College of Chemistry and Molecular EngineeringPeking UniversityBeijing100871PR China

Sodium borohydride(NaBH_(4)) is considered as the most potential hydrogen storage material for portable proton exchange membrane fuel cells(PEMFC)because of its high theoretical hydrogen ***,the slow and poor kinetic stability of hydrogen generation from NaBH_(4) hydrolysis limits its *** are two main factors influencing the kinetics stability of hydrogen generation from NaBH_(4).One factor is that the alkaline byproducts(NaBO_(2)) of the hydrolysis reaction can increase the pH of the solution,thus inhibiting the reaction *** mainly happens in the NaBH_(4) solution hydrolysis *** factor is that the monotonous increase in reaction temperature leads to uncontrollable and unpredictable hydrolysis rates in the solid NaBH_(4) hydrolysis *** is due to the excess heat generated from this exothermic reaction in the initial reaction of NaBH_(4) *** this perspective,we summarize the latest research progress in hydrogen generation from NaBH_(4) and emphasize the design principles of catalysts for hydrogen generation from NaBH_(4) solution and solid state NaBH_(4).The importance of carbon as catalyst support material for NaBH_(4) hydrolysis is also highlighted.

关键词： NaBH_(4)hydrolysis Hydrogen generation Catalyst Kinetics Carbon support materials

Chaotic CS Encryption:An Efficient Image Encryption Algorithm Based on Chebyshev Chaotic System and Compressive Sensing

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第5期79卷 2625-2646页

作者： Mingliang sun jie Yuan Xiaoyong li Dongxiao liu Key Laboratory of Trustworthy Distributed Computing and Service(BUPT) Ministry of EducationBeijing University of Posts and TelecommunicationsBeijing100876China

Images are the most important carrier of human information. Moreover, how to safely transmit digital imagesthrough public channels has become an urgent problem. In this paper, we propose a novel image encryptionalgorithm, called chaotic compressive sensing (CS) encryption (CCSE), which can not only improve the efficiencyof image transmission but also introduce the high security of the chaotic system. Specifically, the proposed CCSEcan fully leverage the advantages of the Chebyshev chaotic system and CS, enabling it to withstand various attacks,such as differential attacks, and exhibit robustness. First, we use a sparse trans-form to sparse the plaintext imageand then use theArnold transformto perturb the image pixels. After that,we elaborate aChebyshev Toeplitz chaoticsensing matrix for CCSE. By using this Toeplitz matrix, the perturbed image is compressed and sampled to reducethe transmission bandwidth and the amount of data. Finally, a bilateral diffusion operator and a chaotic encryptionoperator are used to perturb and expand the image pixels to change the pixel position and value of the compressedimage, and ultimately obtain an encrypted image. Experimental results show that our method can be resistant tovarious attacks, such as the statistical attack and noise attack, and can outperform its current competitors.

关键词： Image encryption chaotic system compressive sensing arnold transform

Gas film/regenerative composite cooling characteristics of the liquid oxygen/liquid methane (LOX/LCH4) rocket engine

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 Zhejiang University-Science A(Applied Physics & Engineering) 2024年第8期25卷 631-649页

作者： Xinlin liU Jun sun Zhuohang JIANG Qinglian li Peng CHENG jie SONG Science and Technology on Scramjet Laboratory College of Aerospace Science and EngineeringNational University of Defense TechnologyChangsha 410073China

The thermal protection of rocket engines is a crucial aspect of rocket engine *** this paper,the gas film/regenerative composite cooling of the liquid oxygen/liquid methane(LOX/LCH4)rocket engine thrust chamber was investigated.A gas film/regenerative composite cooling model was developed based on the Grisson gas film cooling efficiency formula and the one-dimensional regenerative cooling *** accuracy of the model was validated through experiments conducted on a 6 kg/s level gas film/regenerative composite cooling thrust ***,key parameters related to heat transfer performance were *** results demonstrate that the model is sufficiently accurate to be used as a preliminary design *** temperature rise error of the coolant,when compared with the experimental results,was found to be less than 10%.Although the pressure drop error is relatively large,the calculated results still provide valuable guidance for heat transfer *** addition,the performance of composite cooling is observed to be superior to regenerative *** the gas film flow rate results in higher cooling efficiency and a lower gas-side wall ***,the position at which the gas film is introduced greatly impacts the cooling *** optimal introduction position for the gas film is determined when the film is introduced from a single row of *** optimal introduction position results in a more uniform wall temperature distribution and reduces the peak ***,it is observed that a double row of holes,when compared to a single row of holes,enhances the cooling effect in the superposition area of the gas film and further lowers the gas-side wall *** results provide a basis for the design of gas film/regenerative composite cooling systems.

关键词： liquid oxygen/liquid methane(LOX/LCH4)rocket engine Gas film cooling Regenerative cooling Heat transfer characteristics

The MELD scoring system for predicting prognosis in patients with severe hepatitis after plasma exchange treatment

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Hepatobiliary & Pancreatic Diseases International 2007年第5期6卷 492-496页

作者： Yu, Jian-Wu Wang, Gui-Qiang Zhao, Yong-Hua sun, li-jie Wang, Shu-Qin li, Shu-Chen Harbin Med Coll Dept Infect Dis Affiliated Hosp 2 Harbin 150086 Peoples R China Peking Univ First Hosp Dept Infect Dis Beijing 100034 Peoples R China

BACKGROUND: Hepatic failure caused by severe hepatitis is a clinical syndrome where the major liver functions, particularly detoxification, synthetic functions, and metabolic regulation are impaired to different degrees, and may result in major life-threatening complications such as hepatic encephalopathy, ascites, jaundice, cholestasis, bleeding and hepatorenal syndrome. Plasma exchange (PE) has been found useful in treating patients with fulminant hepatic failure by removing hepatic toxins and replacement of clotting factors, so PE treatment has temporary supportive effects on liver failure caused by severe viral hepatitis. in this study, our aim was to predict the prognosis of patients with severe hepatitis after PE treatment using the end-stage liver disease (MELD) scoring system. METHODS: Two hundred and twenty patients were randomly divided into PE and control groups, and the MELD score was calculated for each patient according to the original formula. The efficacy of PE was assessed by mortality or improvement in biochemical parameters and MELD score. RESULTS: The levels of total bilirubin and international normalised ratio (INR) in patients whose MELD scores were between 30 and 39 were lower than those before PE treatment, as those in patients whose MELD scores were 40 or higher. The mortality of patients in the PE group with MELD scores from 30 to 39 was 50.0%, while it was 83.3% in the control group (Plity of patients with MELD scores higher than 40 was 90.0% in the PE group and 98.0% in the control group (P>0.05). CONCLUSIONS: PE treatment can decrease the serum total bilirubin level and INR and MELD score of patients with severe hepatitis and improve liver function. Compared with the control group, PE can significantly decrease the mortality of patients with MELD scores from 30 to 39, but has no effect in patients with MELD scores of 40 or higher.

关键词： severe hepatitis model for end-stage liver disease plasma exchange mortality

Atmospheric Deposition-Carried Pb, Zn, and Cd from a Zinc Smelter and Their Effect on Soil Microorganisms

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2009年第4期19卷 422-433页

作者： YANG Yuan-Gen2, JIN Zhi-Sheng, BI Xiang-Yang, li Fei-li, sun li, liU jie and FU Zhi-You Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002 (China) Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 (China)

Dust emissions from smelters, as a major contributor to heavy metal contamination in soils, could severely influence soil quality. Downwind surface soils within 1.5 km of a zinc smelter, which was active for 10 years but ceased in 2000, in Magu Town, Cuizhou Province, China were selected to examine Pb, Zn, and Cd concentrations and their fractionation along a distance gradient from a zinc smelter, and to study the possible effects of Pb, Zn, and Cd accumulation on soil microorganisms by comparing with a reference soil located at a downwind distance of 10 km from the zinc smelter. Soils within 1.5 km of the zinc smelter accumulated high levels of heavy metals Zn （508 mg kg^-1）, Pb （95.6 mg kg^-1）, and Cd （5.98 mg kg^-1） with low ratios of Zn/Cd （59.1-115） and Pb/Cd （12.4-23.4）. Composite pollution indices （CPIs） of surface soils （2.52-15.2） were 3 to 13 times higher than the reference soils. In metal accumulated soils, exchangeable plus carbonate-bound fractions accounted for more than 10% of the total Zn, Pb, and Cd. The saturation degree of metals （SDM） in soils within 1.5 km of the smelter （averaging 1.25） was six times higher than that of the reference soils （0.209）. A smaller soil microbial biomass was found more frequently in metal accumulated soils （85.1-438 μg C g^-1） than in reference soils （497 μg C g^-1）, and a negative correlation （P 〈 0.01） of soil microbial biomass carbon to organic carbon ratio （Cmic/Corg） with SDM was observed. Microbial consumption of carbon sources was more rapid in contaminated soils than in reference soils, and a shift in the substrate utilization pattern was apparent and was negatively correlated with SDM （R = -0.773, P 〈 0.01）. Consequently, dust deposited Pb, Zn, and Cd in soils from zinc smelting were readily mobilized, and were detrimental to soil quality mainly in respect of microbial biomass .

关键词： composite pollution index heavy metals microbial biomass saturation degree of metals sequential extrac- tion