oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 286 )

2018 ( 5811 )

2017 ( 5932 )

2016 ( 6324 )

Custom range...

Search Results: 1 - 10 of 252400 matches for " 李聪 "
All listed articles are free for downloading (OA Articles)
Page 1 /252400
Display every page Item
激光熔覆制备楔块高硬度层的工艺方法研究
Study on the Process of Wedge High Hardness Layer by Laser Cladding
 [PDF]

, 胡肇炜
Material Sciences (MS) , 2016, DOI: 10.12677/MS.2016.61004
Abstract:
楔块是电梯安全钳中重要的零部件,实际工况要求楔块表面具有高硬度的特点。本文以Q235钢为基体,以含WC的镍基合金粉末为熔覆材料,采用激光熔覆技术制备了大面积的熔覆层。采用扫描电镜、能谱仪对熔覆层进行了微观组织的分析,测试了熔覆层、结合处以及基体的硬度。研究表明以Q235钢为基体时,在激光功率1200 W至2000 W之间,扫描速度在2 mm/s左右时能获得表面质量良好的熔覆层。由于涂层中不同部位的成分、温度分布及冷速不同,组织中析出了多种尺寸及形态的WC颗粒,基体组织梯度特征明显,实现了涂层与基体间的冶金结合。熔覆层表面硬度高达1100 HV以上。
Wedge is an important part of elevator safety gear, the surface should have high hardness as the demand of working condition. Layers are prepared by laser cladding, and the matrix is Q235 steel, cladding powder is Ni base alloy with WC. The scanning electronic microscope and energy disper-sive spectrometer are applied to analyze microstructures and element of particle phase surface. The hardness of layer is also tested. It shows that when laser power is controlled at 1200 W to 2000 W and scanning speed is about 2 mm/s, good quality layer is manufactured. Because of the different composition, temperature and cooling rate, WC particles with various sizes and shapes are precipitated in the layer. The microstructure of the matrix shows an obvious gradient. The layer and matrix are metallurgically bonded. The hardness of layer is above 1100 HV.
ecrec:基于协同过滤的电子商务个性化推荐管理*

现代图书情报技术 , 2009,
Abstract: ?为了使电子商务网站能够提供基于协同过滤的个性化推荐管理,提出并实现一个电子商务协同过滤原型系统ecrec。该系统包含两个基本算法和4个改进算法,其结构独立于电子商务业务系统,具有良好的可移植性和可维护性;同时内嵌算法接口,具有开放式架构的特征,网站可以根据需要向ecrec中增加更多的协同过滤算法。
热风和中短波红外干燥对桃渣干燥特性及多酚含量的影响

- , 2017, DOI: 10.13982/j.mfst.1673-9078.2017.12.022
Abstract: 试验研究了桃渣在60 ℃、70 ℃和80 ℃条件下热风干燥和中短波红外干燥的干燥特性、有效水分扩散系数和活化能,建立了桃渣干燥的数学模型,并比较了桃渣在不同干燥条件下多酚的含量。结果表明,对文中所建立的5种干燥模型进行对比可以发现,Midilli et al.模型最适合描述桃渣在所有干燥条件下的干燥特性(R2>0.9996);桃渣热风干燥的有效水分扩散系数为(1.1652~1.7393)×10-9 m2/s,红外干燥的为(1.6718~2.4993)×10-9 m2/s;利用阿伦尼乌斯方程计算桃渣两种干燥方式的活化能分别为19.56及19.68 kJ/mol。此外,相同干燥温度下红外干燥样品中的总酚保留率较高,分别为68.22%、75.42%及82.63%。与热风干燥相比,桃渣中短波红外干燥速率较大,多酚保留率较高,且多酚含量随干燥温度的升高而增大,80 ℃红外干燥对桃渣的多酚含量影响最小。本试验为桃渣不同干燥条件下的干燥特性以及多酚的利用提供了理论基础。
The drying characteristics, effective moisture diffusivity (Deff) and activation energy (Ea) of peach pomace under hot-air drying (HAD) as well as short- and medium-wave infrared radiation drying (IRD) at 60 ℃, 70 ℃ and 80 ℃ were investigated. The mathematical models of peach pomace under different drying processes were established and the total polyphenol contents of peach pomace under different drying conditions were tested. The results showed that the Midilli et al. model was the best model to describe the drying process of peach pomace under all drying conditions (R2>0.9996) as compared with the five drying models established in this study. The values of effective moisture diffusivity varied from 1.1652×10-9 to 1.7393×10-9 m2/s for HAD and from 1.6718×10-9 to 2.4993×10-9 m2/s for IRD. The activation energies of HAD and IRD methods for peach residue calculated by Arrhenius equation were 19.56 kJ/mol and 19.68 kJ/mol, respectively. In addition, the total polyphenol retention in the IRD samples were 68.22%, 75.42% and 82.63%, which were higher than that in HAD samples at the same drying temperature. In conclusion: the drying rate and polyphenol content of peach pomace under IRD were higher than those under HAD, and the content of polyphenol increased with the increasing drying temperature. The IRD process at 80 ℃ had the minimal effect on the polyphenol content of peach pomace. This study provided the theoretical basis for the drying characteristics of peach pomace under different drying conditions and the usage of polyphenol in the future.
市售盐水鸭挥发性风味物质研究分析

- , 2016, DOI: 10.13982/j.mfst.1673-9078.2016.12.053
Abstract: 为探明南京盐水鸭挥发性风味物质,以不同品牌和不同产品执行标准的6种市售盐水鸭为研究对象,采用固相微萃取-气相色谱-质谱联用技术(SPME-GC-MS)、电子鼻和全自动氨基酸分析仪三种技术,对不同品牌盐水鸭的气味和滋味从微观及宏观角度进行分析。SPME-GC-MS结果表明:从6种盐水鸭中共鉴定出65种挥发性化合物,其中醛类16种、烃类19种、酯类4种、酮类5种、醇类6种、酸类4种与其它11种。6种样品共有化合物为10种(醛类7种、烃类2种与醇类1种)。采用“OAV值”法确定盐水鸭关键风味化合物主要为醛类。由于各样品间挥发性化合物成分不完全相同,导致各品牌盐水鸭整体香气存在差异,该试验结果与电子鼻分析结果一致。氨基酸分析结果显示,盐水鸭样品氨基酸总含量在700~1400 ng/20 μL之间,氨基酸种类和含量无明显差异(p>0.05),市售盐水鸭在滋味上差异不大。
To identify the different volatile flavor compounds among Nanjing salted ducks, six kinds of commercially-available salted ducks of different brands and products were used as samples. Solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS), electronic nose, and an automatic amino acid analyzer were used to perform a comprehensive analysis of the aroma and taste of different brands of salted duck from a macroscopic and microscopic perspective. The result of SPME-GC-MS showed that there were 65 types of volatile compounds in the six brands of salted duck. Among them, there were 16 aldehydes, 19 hydrocarbons, four esters, five ketones, six alcohols, four acids, and 11 other compounds. Ten compounds were found in all six samples (seven aldehydes, two hydrocarbons, and one alcohol). Using the OAV method, we confirmed that the aldehydes were the key flavor compounds of salted duck. The differences in the volatile compounds among the six samples led to differences in the overall aroma among the different brands. The results are consistent with the electronic nose experiment. The result of amino acid analysis showed that the total content of amino acids in the salted ducks was 700~1400 ng/20 μL. There were no significant differences in amino acid type and content among the samples of salted duck (p>0.05), and the difference in taste among the salted ducks was not significant.
木瓜提取物对小鼠脂肪肝的保护作用

- , 2018, DOI: 10.13982/j.mfst.1673-9078.2018.7.005
Abstract: 本文研究了木瓜提取物对小鼠脂肪肝的干预作用。将40只雄性昆明小鼠随机分成4组,正常组、高脂组和药物低(100 mg/kg)、高(300 mg/kg)剂量组。正常组给予普通饲料,高脂组给予高脂高糖饲料,用药组采用木瓜提取物低、高剂量饲料喂养,1月后处死,检测小鼠血清相关指标,HE染色观察肝脏组织形态,RT-PCR和激光共聚焦显微镜(Confocal)检测脂代谢相关基因表达,qPCR检测miR-199a-5p水平。与正常组相比,高脂组小鼠血清中TC、ALT的水平增高;组织病理结果显示,肝脏脂肪变性明显;RT-PCR和Confocal结果显示,HGF、VEGFa和c-Met的表达降低,qPCR显示,高脂组中miR-199a-5p水平增高。与高脂组比较,药物低、高剂量组脂肪肝病理损伤明显改善,血清ALT、TC含量均下降,HGF、VEGFa和c-Met表达水平上调,miR-199a-5p水平降低。因此木瓜提取物对高脂高糖诱导的小鼠脂肪肝有保护作用,其可能的机制是通过调节miR-199a-5p-HGF/c-Met信号通路发挥作用。
The protective effects of active components extracted from Chaenomeles Speciosa (EACCS) on non-alcoholic fatty liver disease (NAFLD) in mice were investigated. Forty male KM mice were equally randomized into four groups, namely, normal group, model group, low-dose EACCS group (100 mg/kg body weight/day), and high-dose EACCS group (300 mg/kg body weight/day). The normal group was fed with a normal diet, the model group was given a high-fat–high-fructose diet (HFFD), and the low-dose and high-dose EACCS groups were given HFFD followed by EACCS at low- and high-dose, respectively. Body weights were monitored. The mice were sacrificed 1 month later and serum-based biomarkers and morphology of liver tissue were examined. Real-time (RT)-PCR and confocal microscopy techniques were used to detect the expression of lipid metabolism-related genes. Compared with the normal group, the serum alanine aminotransferase (ALT) and total cholesterol (TC) of the model group increased, indicating significant steatosis; The expression levels of hepatocyte growth factor (HGF), vascular endothelial growth factor-A (VEGF-A) and c-Met also decreased in the model group, whilst the expression level of miR-199a-5p increased. Compared with the model group, the hepatic lipid accumulation of EACCS groups was obviously suppressed with significantly decreased serum ALT and TC levels and the expression levels of hepatic HGF, VEGFa and c-Met mRNA increased; and the expression levels of miR-199a-5p increased. Therefore, EACCS has protective effects on NAFLD mice induced by HFFD, and its mechanism may be related to the activation of miR-199a-5p-HGF/c-Met signaling pathway in the liver tissues.
桃渣真空干燥特性数学建模

- , 2017, DOI: 10.13982/j.mfst.1673-9078.2017.10.013
Abstract: 为了探究干燥模型在真空干燥中的应用,试验以桃渣在不同真空干燥温度(55、65、75和85 ℃)下的干燥过程为研究对象,利用10种薄层干燥模型对其干燥特性曲线进行拟合分析,并计算其有效水分扩散系数和活化能。结果表明:干燥温度对桃渣干燥速率的影响较大,干燥时间随着干燥温度的升高而减少;桃渣干燥的主要阶段发生在降速干燥阶段。通过对文中10种薄层干燥模型的拟合结果进行对比可以发现,Wang and singh模型对桃渣干燥的拟合性较好(R2>0.99776),模型的预测值与试验值能较好吻合,适合描述桃渣在所有干燥条件下的干燥特性;根据费克第二定律获得桃渣真空干燥的有效水分扩散系数范围为8.0855×10-10~1.5340×10-9 m2/s,且随干燥温度的升高而增大;利用阿伦尼乌斯方程计算桃渣真空干燥的活化能为21.1 kJ/mol。本研究为真空干燥技术应用于桃渣的干燥提供了理论基础。
The drying characteristics, effective moisture diffusivity (Deff) and activation energy (Ea) of peach pomace with vacuum drying at 55 ℃, 65 ℃, 70 ℃ and 80 ℃ were investigated in this study. The experimental data obtained were fitted to ten thin-layer drying models. The results indicated that drying temperature had a significant influence on the drying rate of peach pomace. The drying time decreased with the increasing drying temperature, and the drying process appeared in the falling rate periods. Compared the results of ten thin-layer drying models, models of Wang and singh were the best to describe the drying process of peach pomace under all drying conditions (R2 > 0.99776), and there was a good agreement between the experimental and predicted values. According to the Fick’s second law, the values of effective moisture diffusivity varied from 8.0855×10-10~1.5340×10-9 m2/s. The relationship between the effective moisture diffusivity and drying temperature could be described by Arrhenius-type relationship, which resulted in activation energy of 21.1 kJ/mol for peach pomace. This study provides a theoretical basis for the application of vacuum drying technology in the drying of peach pomace.
综合分析本科生毕业论文质量问题并对此问题提出几点建议
Comprehensive Analysis on Graduation Thesis’s Quality Problems of Undergraduates and Some Suggestions on This Problem
 [PDF]

万响亮,, 光强
Vocational Education (VE) , 2015, DOI: 10.12677/VE.2015.43005
Abstract:
本科生的毕业论文是大学课程设置中的重要组成部分,但目前存在着我国高校的本科毕业论文质量有不同程度下降的问题。如何提高本科毕业论文质量的问题,一直以来为高校所关注和思考。笔者在参阅相关文献的基础上,综合分析本科生毕业论文质量问题并提出几点建议。
Graduation thesis of undergraduates is an important part of college curriculum, but the quality decline of undergraduates’ graduation thesis is a serious problem at present in our country. The problem of how to improve the quality of the undergraduates’ graduation thesis has long been a concern and thinking of colleges and universities. This paper, referring to the related literatures, comprehensively analyzes the graduation thesis quality problems of undergraduates and puts forward some suggestions.
基于数值模拟的滑带土蠕变特性研究
,,,
安全与环境工程 , 2014,
Abstract: 选取黄土坡临江Ⅱ号崩滑堆积体上TP4平硐内的滑带土进行了室内三轴蠕变试验,选择Burgers蠕变方程对参数进行辩识,并利用FLAC3D对室内三轴蠕变试验进行了数值模拟,在此基础上对滑带土的蠕变特性及其长期强度进行了研究。结果表明滑带土的流变性较强;数值模拟试验结果与室内三轴蠕变试验结果具有很好的相似性;利用数值模拟试验结果可以获取滑带土分别加载下的等时曲线,最后可得到滑带土的长期强度参数(即内聚力c∞为21.2kPa、内摩擦角φ∞为18.56°),这为进一步研究滑坡的长期稳定性奠定了基础。
基于实数编码的广义遗传算法及其在优化问题中的应用
 鹏,董 
控制与决策 , 2002,
Abstract: 对遗传算法中一些具有代表性的算法作了简要分析和评论。在此基础上将实数编码引入广义遗传算法,给出了一个算法框架,设计了相应的遗传操作方法,并将该算法应用于函数优化问题和神经网络训练问题。数值算例表明,该方法具有全局优化功能和快速收敛特性,对于求解复杂优化问题具有广泛的适用性。
滇西南地区地壳速度结构的区域波形反演
,雷建设
科学通报 , 2014, DOI: 10.1360/N972014-00407
Abstract: 利用中国地震局地壳应力研究所于2010~2011年在滇西南地区布设的宽频带流动地震台所记录的三分量高质量波形资料,采用小生境遗传算法通过波形反演,获得了研究区P波速度模型.结果显示,滇西南地区地壳厚度为38~43km,上地幔顶部平均速度为7.9km/s,地壳速度存在明显的横向不均匀性.思茅地块的上地壳和下地壳厚度均呈现出明显的由南向北、自东向西增厚趋势,说明该地块地壳增厚由上地壳和下地壳共同增厚形成.腾冲地块中地壳和下地壳的平均厚度及速度均小于保山地块和思茅地块,思茅地块部分路径上的下地壳和上地幔速度均较低,可能与印度板块东向俯冲引起地幔热物质上涌等动力过程密切相关.这些结果对于认识青藏高原形成与演化动力过程提供重要地震学约束.
Page 1 /252400
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.