期刊文献+
共找到171篇文章
< 1 2 9 >
每页显示 20 50 100
聂华苓的翻译共同体研究:合/和译、创译与世界主义
1
作者 谢攀 樊星 《华文文学》 2023年第4期81-87,共7页
华人小说家聂华苓与美国诗人保罗·安格尔(Paul Engle)于1967年创办了“国际写作计划”,该计划是一个以翻译活动为基石的文学共同体。在主持该项目期间,聂华苓主持编纂、亲自翻译了多部作品,并提出“合译”模式与“和译”思维,以化... 华人小说家聂华苓与美国诗人保罗·安格尔(Paul Engle)于1967年创办了“国际写作计划”,该计划是一个以翻译活动为基石的文学共同体。在主持该项目期间,聂华苓主持编纂、亲自翻译了多部作品,并提出“合译”模式与“和译”思维,以化解不同成员间由于不同背景和语言差异所产生的文化碰撞。基于该翻译思维,聂华苓在翻译汉诗时保留原诗意象,并借用语法功能强化意象的感知方式,实现了创造性翻译,构建了译者、合译者、作者和读者之间超越单一文本的立体平台。在这个文学共同体之下,聂华苓以生命经验的共性为依托,将翻译作为她思考人类共同命运的重要面向。 展开更多
关键词 聂华苓 翻译共同体 /和译 国际写作计划 世界主义
下载PDF
Electrical Performance of Static Induction Transistor with Mixed I-V Characteristics
2
作者 王永顺 刘肃 +1 位作者 李思渊 胡冬青 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2004年第3期266-271,共6页
The mixed non-saturating I-V characteristics of static induction transistor (SIT) are investigated.The optimum matching relations among the structural,material,and technological parameters are also presented.The techn... The mixed non-saturating I-V characteristics of static induction transistor (SIT) are investigated.The optimum matching relations among the structural,material,and technological parameters are also presented.The technological experiments demonstrate that the channel parameters play a critical role in determining whether it is a mixed,triode-like or pentode-like I-V characteristics.The general control principles,methods,and criterions of fabrication parameters as well as the effect of control factor are analytically discussed.The results are useful for design and fabrication of SIT,especially for SIT with mixed I-V characteristics. 展开更多
关键词 static induction transistor PINCH-OFF mixed characteristics SATURATION
下载PDF
FORTY-EIGHT CASES OF ACUTE GOUTY ARTHRITIS TREATED COMPREHENSIVELY WITH ELECTROACUPUNCTURE AND WARMING MOXIBUSTION
3
作者 陈英 曹晶晶 《World Journal of Acupuncture-Moxibustion》 2008年第2期16-19,70,共5页
Objective To probe into the effects on acute gouty arthritis treated comprehensively with electroacupuncture (EA) and warming moxibustion. Methods 70 cases were randomized into treatment group (48 cases), in which the... Objective To probe into the effects on acute gouty arthritis treated comprehensively with electroacupuncture (EA) and warming moxibustion. Methods 70 cases were randomized into treatment group (48 cases), in which the EA+warming moxibustion was applied; and controlled group (22 cases), in which, colchicine was prescribed for oral administration. Results The statistical outcomes after 1 course treatment in treatment group: 28 cases were cured (58.33%), 18 cases improved (37.50%) and the total effective rate was 95.83%. In controlled group: 12 cases (54.55%) were cured, 8 cases improved (36.36%) and the total effective rate was 90.91%. The therapeutic effects of two groups were basically consistent, without significant different (P>0.05). But, concerning to side effect, there was no any toxic side effects in the group treated with EA+warming moxibustion, and the occurrence rate in the group treated with colchicine was 40.91%. Conclusion Electroacupuncture+warming moxibustion achieves good therapeutic effects without any side effects. 展开更多
关键词 Electroacupuncture (EA) Warming Moxibustion Massage Gouty arthritis
下载PDF
Low complexity joint source-channel decoding for transmission of wavelet compressed images
4
作者 殷玮玮 梅中辉 吴乐南 《Journal of Southeast University(English Edition)》 EI CAS 2006年第2期148-152,共5页
To utilize residual redundancy to reduce the error induced by fading channels and decrease the complexity of the field model to describe the probability structure for residual redundancy, a simplified statistical mode... To utilize residual redundancy to reduce the error induced by fading channels and decrease the complexity of the field model to describe the probability structure for residual redundancy, a simplified statistical model for residual redundancy and a low complexity joint source-channel decoding(JSCD) algorithm are proposed. The complicated residual redundancy in wavelet compressed images is decomposed into several independent 1-D probability check equations composed of Markov chains and it is regarded as a natural channel code with a structure similar to the low density parity check (LDPC) code. A parallel sum-product (SP) and iterative JSCD algorithm is proposed. Simulation results show that the proposed JSCD algorithm can make full use of residual redundancy in different directions to correct errors and improve the peak signal noise ratio (PSNR) of the reconstructed image and reduce the complexity and delay of JSCD. The performance of JSCD is more robust than the traditional separated encoding system with arithmetic coding in the same data rate. 展开更多
关键词 joint source-channel decoding sum-product algorithm generalized distribution law wavelet compressed image
下载PDF
Feature combination via importance-inhibition analysis
5
作者 杨思春 高超 +2 位作者 姚佳岷 戴新宇 陈家骏 《Journal of Southeast University(English Edition)》 EI CAS 2013年第1期22-26,共5页
A new method for combining features via importance-inhibition analysis (IIA) is described to obtain more effective feature combination in learning question classification. Features are combined based on the inhibiti... A new method for combining features via importance-inhibition analysis (IIA) is described to obtain more effective feature combination in learning question classification. Features are combined based on the inhibition among features as well as the importance of individual features. Experimental results on the Chinese questions set show that, the IIA method shows a gradual increase in average and maximum accuracies at all feature combinations, and achieves great improvement over the importance analysis(IA) method on the whole. Moreover, the IIA method achieves the same highest accuracy as the one by the exhaustive method, and further improves the performance of question classification. 展开更多
关键词 question answering system questionclassification feature combination importance-inhibitionanalysis
下载PDF
Tuning of the textural features and acidic properties of sulfated mesoporous lanthana-zirconia solid acid catalysts for alkenylation of diverse aromatics to their corresponding α-arylstyrenes
6
作者 赵忠奎 冉金凤 +2 位作者 郭永乐 苗博元 王桂茹 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 北大核心 2016年第8期1303-1313,共11页
The textural features and acidic properties of sulfated mesoporous lanthana‐zirconia solid acids (SO42?/meso‐La0.1Zr0.9Oδ) were efficiently tuned by modifying the conditions used to prepare the meso‐La0.1Zr0.9O... The textural features and acidic properties of sulfated mesoporous lanthana‐zirconia solid acids (SO42?/meso‐La0.1Zr0.9Oδ) were efficiently tuned by modifying the conditions used to prepare the meso‐La0.1Zr0.9Oδcomposites, such as the molar ratio of the template to La and Zr metal ions (Nt/m), molar ratio of ammonia to La and Zr metal ions (Na/m), hydrothermal temperature (Thydro), and hy‐drothermal time (thydro). The effect of the textural features and acidic properties on the catalytic performance of solid acid catalysts for alkenylation of p‐xylene with phenylacetylene was investi‐gated. Various characterization techniques such as N2 physisorption, X‐ray diffraction, NH3 temper‐ature‐programmed desorption, and thermogravimetric analysis were employed to reveal the rela‐tionship between the nature of catalyst and its catalytic performance. It was found that the catalytic performance significantly depended on the textural features and acidic properties, which were strongly affected by preparation conditions of the meso‐La0.1Zr0.9Oδcomposite. Appropriate acidic sites and high accessibility were required to obtain satisfactory catalytic reactions for this reaction. It was also found that the average crystallite size of t‐ZrO2 affected by the preparation conditions had significant influence on the ultrastrong acidic sites of the catalysts. The optimized SO42?/meso‐La0.1Zr0.9Oδcatalyst exhibited much superior catalytic activity and coke‐resistant stabil‐ity. Moreover, the developed SO42?/meso‐La0.1Zr0.9Oδcatalyst demonstrated excellent catalytic per‐formance for alkenylation of diverse aromatics with phenylacetylene to their correspondingα‐arylstyrenes. Combining the previously established complete regeneration of used catalysts by a facile calcination process with the improved catalytic properties, the developed SO42?/meso‐La0.1Zr0.9Oδ solid acid could be a potential catalyst for industrial production ofα‐arylstyrenes through clean and atom efficient solid‐acid‐mediated Friedel‐Crafts alkenylation of diverse aromatics with phenylacetylene. 展开更多
关键词 Mesoporous solid acid ALKENYLATION Clean synthesis Alkenyl aromatics Textural and acidic properties Tuning
下载PDF
科技文献中的“亲和”与“亲合”辨析 被引量:1
7
作者 向东 《编辑学报》 CSSCI 北大核心 2008年第4期298-299,共2页
列举科技文献中"亲和"和"亲合"的错误用法,对二者的正确使用提出了建议。
关键词 亲和 辨析
下载PDF
Responses of Photosynthetic Pigment, Phenol and Total Saponin Contents of Panax notoginseng to Supplemental UV-B under Field Conditions
8
作者 赵昶灵 陈中坚 +4 位作者 魏富刚 李孙文 杨莉 李俊 王崇德 《Agricultural Science & Technology》 CAS 2014年第7期1120-1124,1151,共6页
[Objective] The aim of this study was to investigate the content changes and their correlations of the photosynthetic pigment,phenols,including total phenols,total flavonoids and anthocyanins,and total saponins of the... [Objective] The aim of this study was to investigate the content changes and their correlations of the photosynthetic pigment,phenols,including total phenols,total flavonoids and anthocyanins,and total saponins of the one-year-old P.notoginseng plants under supplemental UV-B stress in fields.[Method] The one-year-old plants were irradiated by UV-B in field for 1 min per day,and the plants under the UV-B lamp were regarded as a circle center,achieving an annular leaf-sampling.The photosynthetic pigment,phenols and total saponins of the leaves were determined spectrophotometrically.[Result] With the increase of sampling radius,the supplemental UV-B intensity decreased significantly,the contents of chlorophyll (Chl) a,Chl b,Chl (a+b),carotenoid (Car) and total photosynthetic pigment (Chl+Car) of the leaves increased extremely significantly,the Chl a/b and total phenol content (TPC) decreased extremely significantly,but the Chl (a+b)/Car changes were not significant.The contents of total flavonoids,anthocyanins and saponins all increased due to the increasing of UV-B,displaying dose effects.The UV-B intensity was positively correlated with the Chl a/b,and negatively with the Chl a,Chl b,Chl (a+ b),Car and (Chl+Car) contents; and the two of TPC,total flavonoid content (TFC),total anthocyanin content (TAC) and total saponin content (TSC) were positively correlated,all reaching extremely significant level.The UV-B intensity was positively and significantly correlated with the total flavonoid content (TFC),negatively and significantly with the Chl (a+b)/Car,and positively and insignificantly with the TPC,TAC and TSC.[Conclusion] For one-year-old plants of P.notoginseng,UV-B can decrease the contents of the Chl a,Chl b,Chl (a+b),Car and (Chl+Car) and increase the Chl a/b and TPC,and,furthermore,induce the increases of the TFC,TAC and TSC in a dose-dependent manner.However,UV-B can hardly change the Chl (a+b)/Car.The supplemental UV-B of well-suited dose might be one of the effective measures to improve the TSC of P.notoginseng. 展开更多
关键词 One-year-old Panax notoginseng plants Photosynthetic pigment Phenol and total saponin contents Supplemental UV-B Response
下载PDF
Effects of frothers on bubbles size and flotation performance of hydrophobic minerals
9
作者 Gülşah GÜVEN Berivan TUNÇ +1 位作者 Ş.Beste AYDIN Gülay BULUT 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第7期2280-2299,共20页
Frothers facilitate the reduction of bubbles size by preventing bubbles coalescence and produce more stable froths.The collision probability of the bubbles and particles substantially increases by decreasing bubble si... Frothers facilitate the reduction of bubbles size by preventing bubbles coalescence and produce more stable froths.The collision probability of the bubbles and particles substantially increases by decreasing bubble size.For the same volume system,fewer bubbles result from a distribution of large-sized bubbles,and more bubbles result from a distribution of small-sized bubbles.In this research,fundamental two-phase frother characterization parameters were aimed to link with three-phase coal and talc flotation behavior.For this purpose,the effect of single and dual frother systems on inhibiting bubble coalescence was investigated with methyl isobutyl carbinol(MIBC),isooctanol(2 ethyl hexanol),pine oil,and Dowfroth 250.Based on the results of single frothers,isooctanol at the lowest critical coalescence concentration(CCC)value of 6×10^(−6) achieved the smallest bubbles with Sauter mean diameter of 0.80 mm.By blending Dowfroth 250 and pine oil,the bubbles size decreased significantly,reaching 0.45 mm.While the highest recoveries in coal flotation were obtained in single and frother blends where the bubbles size was measured as the smallest in two-phase system,and such a relationship was not found for talc flotation. 展开更多
关键词 FLOTATION frother blends bubble size coal and talc flotation
下载PDF
Affinity Chromatography Purification of Recombinant Human Interleukin-6 from Its Fusion Protein with GST
10
作者 吴蕾 甘一如 +1 位作者 林峰 黄鹤 《Transactions of Tianjin University》 EI CAS 2002年第2期106-109,共4页
Recombinant E.coli JM109, containing pHZ1818 plasmid which included the fused gene encoding human interleukin 6(IL 6), expressed a fusion protein with glutathion S transferase(GST). The fusion protein existed both... Recombinant E.coli JM109, containing pHZ1818 plasmid which included the fused gene encoding human interleukin 6(IL 6), expressed a fusion protein with glutathion S transferase(GST). The fusion protein existed both in the supernatant and inside the bacterial cell,but the insoluble protein had no biological activity and could not be refolded. The rotative speed of the shaker and the temperature of induction were optimized to maximize the expression of the soluble fusion protein. From the supernatant of the cell sonicates Glutathion Sephrose 4B affinity column chromatography was employed to isolate the fusion protein which could be purified to >80 0 0 in a single step. The yield of soluble GST IL 6 was about 10 mg per liter culture. The GST was site specifically cloven by 6 hours of treatment with thrombin and from the thrombin digest mixture IL 6 was purified by Q high performance ion exchange chromatography. From 1 liter of E.coli culture 2 mg refined IL 6 was obtained. The purified IL 6 had a purity of more than 95 0 0 and a biological activity of 1.02×10 8 IU/mg. 展开更多
关键词 affinity purification human interleukin 6 fusion protein GST
下载PDF
Selective laser melted near-beta titanium alloy Ti-5Al-5Mo-5V-1Cr-1Fe:Microstructure and mechanical properties 被引量:5
11
作者 HUANG Hua-long LI Dan +4 位作者 CHEN Chao LI Rui-di ZHANG Xiao-yong LIU Shi-chao ZHOU Ke-chao 《Journal of Central South University》 SCIE EI CAS CSCD 2021年第6期1601-1614,共14页
In this work,a near-beta Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy was fabricated by selective laser melting(SLM),and the microstructure evolution together with the mechanical properties was studied.The as-fabricated alloy... In this work,a near-beta Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy was fabricated by selective laser melting(SLM),and the microstructure evolution together with the mechanical properties was studied.The as-fabricated alloy showed columnarβgrains spreading over multiple layers and paralleling to the building direction.The distinct microstructure of as-fabricated alloy was composed of near-β(more than 98.1%)with a submicron cellular structure.Different SLM processing parameters such as hatch spacing could affect the microstructure of as-fabricated alloy,which could thus further significantly affect the mechanical properties of as-fabricated alloy.In addition,the as-fabricated alloy with the distinct microstructure exhibits yield strength of 818 MPa combined with elongation of more than 19%,which shows that SLM is a potential technology for manufacturing near-beta titanium components. 展开更多
关键词 selective laser melting Ti-5Al-5Mo-5V-1Cr-1Fe near-βandβ-titanium alloy cellular structure PRECIPITATION
下载PDF
Estimation of surface tension of organic compounds using quantitative structure-property relationship 被引量:2
12
作者 戴益民 刘又年 +3 位作者 李浔 曹忠 朱志平 杨道武 《Journal of Central South University》 SCIE EI CAS 2012年第1期93-100,共8页
A novel quantitative structure-property relationship (QSPR) model for estimating the solution surface tension of 92 organic compounds at 20℃ was developed based on newly introduced atom-type topological indices. Th... A novel quantitative structure-property relationship (QSPR) model for estimating the solution surface tension of 92 organic compounds at 20℃ was developed based on newly introduced atom-type topological indices. The data set contained non-polar and polar liquids, and saturated and unsaturated compounds. The regression analysis shows that excellent result is obtained with multiple linear regression. The predictive power of the proposed model was discussed using the leave-one-out (LOO) cross-validated (CV) method. The correlation coefficient (R) and the leave-one-out cross-validation correlation coefficient (Rcv) of multiple linear regression model are 0.991 4 and 0.991 3, respectively. The new model gives the average absolute relative deviation of 1.81% for 92 substances. The result demonstrates that novel topological indices based on the equilibrium electro-negativity of atom and the relative bond length are useful model parameters for QSPR analysis of compounds. 展开更多
关键词 surface tension quantitative structure-property relationship (QSPR) topological indice organic compound
下载PDF
Long-term changes in sedimentary diatom assemblages and their environmental implications in the Changjiang(Yangtze) River estuary, China 被引量:2
13
作者 程芳晋 俞志明 宋秀贤 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2014年第1期155-161,共7页
Long-term data on diatom assemblages in a sediment core (60 cm) obtained from the Changjiang (Yangtze) River estuary were analyzed in order to assess the environmental changes that took place in the approximately ... Long-term data on diatom assemblages in a sediment core (60 cm) obtained from the Changjiang (Yangtze) River estuary were analyzed in order to assess the environmental changes that took place in the approximately 38 years (as determined by 210pb measurements), i.e., between 1974 and 2012, of sediment accumulation. From the sediment core, 62 diatom taxa and genera were identified. The diatom biomass in the core generally increased beginning in the mid-1990s (core depth: 35 cm), accompanied by a shift in the dominant species from Podosira stelliger and two species of Cyclotella (C. stylorum and C. striata) to Paralia sulcata, three species of Thalassiosira ( T. eccentria, I". oestrupii, and T. excentrica), Actinoptychus undulates, and Thalassionema nitzschioides. The changes in both species diversity and abundance suggested that since the 1980s the estuary has undergone extensive eutrophication. This conclusion was supported by the increased proportion of planktonic species, another indicator of high nutrients inputs, in the Changjiang River estuary. 展开更多
关键词 diatom assemblages Changjiang River estuary East China Sea environmental implications
下载PDF
Combination of Ecoprofile and Least-cost Model for Eco-network Planning 被引量:3
14
作者 XIAO He LIU Yunhui +2 位作者 YU Zhenrong ZHANG Qian ZHANG Xin 《Chinese Geographical Science》 SCIE CSCD 2014年第1期113-125,共13页
The protecting requirements and functional connectivity of species in isolated habitat patches are crucial factors of eco-network planning.This study aimed to improve the method of eco-network planning for species con... The protecting requirements and functional connectivity of species in isolated habitat patches are crucial factors of eco-network planning.This study aimed to improve the method of eco-network planning for species conservation.Ecoprofiling was used to group the species by similar behavior types,namely,choice of ecosystem,area requirement,and short distance dispersal abilities.A least-cost model was used to simulate the optimal corridor location to maintain functional connectivity.A combination of ecoprofile and least-cost model was hired to develop an eco-network that promoted species conservation.A case study was also conducted in Beijing,China.In addition to the required ecosystem,habitat area is an important parameter for habitat extraction.Habitat area can remove noise habitat patches because of lacking area.Short-distance dispersal can be used to identify corridor requirements and avoid unnecessary building requirements.Species with various dispersal abilities exhibit significant differences in terms of corridor length and location requirement.Habitat isolation is the main threat for weakly mobile species,and habitat loss is the major risk of mobile species protection.Different species groups also exhibit distinct landscape pattern demands for an eco-network,and the eco-network planning based on specific species can not protect other species.We proposed that a combination of ecoprofile and least-cost model improved the efficiency of species conservation by eco-network planning. 展开更多
关键词 eco-network ecoprofile least-cost model biodiversity conservation BEIJING China
下载PDF
The relation between modes of lithologic association and interlayer-gliding structures in coal mine 被引量:6
15
作者 LE Qi-lang CHEN Ping YANG Wei-min 《Journal of Coal Science & Engineering(China)》 2010年第1期47-52,共6页
As a case study of the Panji No.1 Coal Mine in Anhui Province, based on thesite measured and statistical data, summarized the lithologic associations, characteristicsand distribution laws of interlayer-gliding structu... As a case study of the Panji No.1 Coal Mine in Anhui Province, based on thesite measured and statistical data, summarized the lithologic associations, characteristicsand distribution laws of interlayer-gliding structures and tectonic coal in the No.11-2 coalseams.The results show that 9 modes of lithologic association can form interlayer-glidingstructures.It is more easy for rock slip to occur when the lithologic associations are mainroof + coal seam + immediate floor type, compound roof+immediate roof + coal seam +immediate floor type and immediate roof + coal seam + immediate floor type.Lithologicassociations of roof and floor are the precondition to the formation of interlayer-glidingstructures. 展开更多
关键词 coal seam roof and floor modes of lithologic association interlayer-gliding structure Panji No.1 Coal Mine
下载PDF
Oxidation of Benzothiophenes Using Tert-amyl Hydroperoxide 被引量:4
16
作者 周新锐 盖洪涛 +3 位作者 王静 张珊珊 杨锦宗 张淑芬 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2009年第2期189-194,共6页
Homogeneous oxidation using an oil-soluble oxidant, tert-amyl hydroperoxide (TAHP), for ultra-deep desulfurization was performed under mild conditions in the presence of molybdenum oxide catalysts. Dibenzothio- phe... Homogeneous oxidation using an oil-soluble oxidant, tert-amyl hydroperoxide (TAHP), for ultra-deep desulfurization was performed under mild conditions in the presence of molybdenum oxide catalysts. Dibenzothio- phene (DBT), benzothiophene (BT) and 4, 6-dimethyl-dibenzothiophene (DMDBT), which are the refractory sulfur compounds for hydrodesulfurization (HDS), were employed as model substrates for a simulated diesel fuel. Activity of molybdenum oxide supported on a macroporous weak acidic resin was investigated. The mass conversion of DBT reached near 100% at 90℃ and a TAHP/DBT molar ratio of 3 with 1% of molybdenum oxide supported on Amberlite IRC-748 resin for 1 h. It was further found that the activities of the model substrates decreased in the or- der of DMDBT 〉DBT 〉BT. In the flow oxidation using TAHP as the oxidant, mass conversion of DBT increased remarkably from 61.3% to 98.5% when dropping the weight hourly space velocity (WHSV) from 40 h^-1 to 10 h^-1. A series of experiments dealt with selectivity of this oxidation using TAHP revealed that the model unsaturated compounds, i.e. 4, 6, 8-trimethyl-2-nonylene, and 2-methylnaphthalene did not affect the oxidation of DBT. Carbazole had nearly no effect on the conversion of DBT using TAHP, but had some influence on the one using tert-butyl hydroperoxide (TBHP). The mass conversion of DBT decreased remarkably from 75.2% to 3.6% when the content of carbazole increased from 0 to 500μg·g^-1. In the flow oxidation using TAHP as the oxidant, the concentration of DBT in model fuels was reduced from 500 μg·g^-1 to 7.2 μg·g^-1 at WHSV of 10 h^-1, and then reduced to 3.8 μg·g^-1 by adsorntion of Al2O3. 展开更多
关键词 DESULFURIZATION BENZOTHIOPHENE tert-amyl hydroperoxide
下载PDF
Effect of Cu-ZnO-Al_2O_3 supported on H-ferrierite on hydrocarbons formation from CO hydrogenation 被引量:2
17
作者 J.H.Flores M.E.H.Maia da Costa M.I.Pais da Silva 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 北大核心 2016年第3期378-388,共11页
Methanol synthesis catalysts based on Cu, Zn and Al were prepared by three methods and subsequently mixed with H-ferrierite zeolite in an aqueous suspension to disperse the catalysts over the support. These materials ... Methanol synthesis catalysts based on Cu, Zn and Al were prepared by three methods and subsequently mixed with H-ferrierite zeolite in an aqueous suspension to disperse the catalysts over the support. These materials were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy, temperature programmed reduction, NH3 and H2 temperature-programmed desorption, and X-ray photoelectron spectroscopy. They were also applied to the CO hydrogenation reaction to produce dimethyl ether and hydrocarbons. The catalysts were prepared by coprecipitation under low and high supersaturation conditions and by a homogeneous precipitation method. The preparation technique was found to affect the precursor structural characteristics, such as purity and crystallinity, as well as the particle size distribution of the resulting catalyst. Low supersaturation conditions favored high dispersion of the Cu species, increasing the methanol synthesis catalyst's metallic surface area and resulting in a homogeneous particle size distribution. These effects in turn were found to modify the zeolite properties, promoting both a low micropore volume and blockage of the zeolite acid sites. The effect of the methanol synthesis catalyst on the reaction was verified by the correlation between the Cu surface area and the CO conversion rate. 展开更多
关键词 Methanol synthesis catalyst Low supersaturation precipitation High supersaturation precipitation SYNGAS HYDROTALCITE HYDROCARBON Dimethyl ether
下载PDF
Synthesis of Novel Fluorinated Acrylate Co-polymers and Their Application on Cotton Fabrics 被引量:1
18
作者 杨彬彬 卿凤翎 孟卫东 《Journal of Donghua University(English Edition)》 EI CAS 2010年第1期19-24,共6页
Two novel fluorinated acrylate monomers 4a and 4b containing perfluorohexyl group were designed and synthesized starting from 4-allylanisole and perfluorohexyl iodide.The monomers 4a and 4b were then copolymerized wit... Two novel fluorinated acrylate monomers 4a and 4b containing perfluorohexyl group were designed and synthesized starting from 4-allylanisole and perfluorohexyl iodide.The monomers 4a and 4b were then copolymerized with octadecyl acrylate and 2-hydroxyethyl acrylate by emulsion polymerization to give copolymers PFA 1 and PFA 2 respectively.The co-polymers were characterized by FT-IR and their heat stability was measured by TGA.The surface properties of PFA 1 and PFA 2 were studied by applying on cotton fabrics.The treated cotton fabrics showed good water-repellent property,and the contact angles for water reached 142° for PFA 1 and 136° for PFA 2. 展开更多
关键词 fluorinated acrylate emulsion polymerization water and oil repellency
下载PDF
A novel hybrid algorithm based on a harmony search and artificial bee colony for solving a portfolio optimization problem using a mean-semi variance approach 被引量:4
19
作者 Seyed Mohammad Seyedhosseini Mohammad Javad Esfahani Mehdi Ghaffari 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第1期181-188,共8页
Portfolio selection is one of the major capital allocation and budgeting issues in financial management, and a variety of models have been presented for optimal selection. Semi-variance is usually considered as a risk... Portfolio selection is one of the major capital allocation and budgeting issues in financial management, and a variety of models have been presented for optimal selection. Semi-variance is usually considered as a risk factor in drawing up an efficient frontier and the optimal portfolio. Since semi-variance offers a better estimation of the actual risk portfolio, it was used as a measure to approximate the risk of investment in this work. The optimal portfolio selection is one of the non-deterministic polynomial(NP)-hard problems that have not been presented in an exact algorithm, which can solve this problem in a polynomial time. Meta-heuristic algorithms are usually used to solve such problems. A novel hybrid harmony search and artificial bee colony algorithm and its application were introduced in order to draw efficient frontier portfolios. Computational results show that this algorithm is more successful than the harmony search method and genetic algorithm. In addition, it is more accurate in finding optimal solutions at all levels of risk and return. 展开更多
关键词 portfolio optimizations mean-variance model mean semi-variance model harmony search and artificial bee colony efficient frontier
下载PDF
Composition-controlled synthesis of platinum and palladium nanoalloys as highly active electrocatalysts for methanol oxidation 被引量:4
20
作者 Haiqiang Zhao Weihong Qi +2 位作者 Xinfeng Zhou Haofei Wu Yejun Li 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 北大核心 2018年第2期342-349,共8页
Platinum and palladium(PtPd)alloy nanoparticles(NPs)are excellent catalysts for direct methanol fuel cells.In this study,we developed PtPd alloy NPs through the co‐reduction of K2PtCl4and Na2PdCl4in a polyol synthesi... Platinum and palladium(PtPd)alloy nanoparticles(NPs)are excellent catalysts for direct methanol fuel cells.In this study,we developed PtPd alloy NPs through the co‐reduction of K2PtCl4and Na2PdCl4in a polyol synthesis environment.During the reaction,the feed molar ratio of the two precursors was carried over to the final products,which have a narrow size distribution with a mean size of approximately4nm.The catalytic activity for methanol oxidation reactions possible depends closely on the composition of as‐prepared PtPd alloy NPs,and the NPs with a Pt atomic percentage of approximately75%result in higher activity and stability with a mass specific activity that is7times greater than that of commercial Pt/C catalysts.The results indicate that through composition control,PtPd alloy NPs can improve the effectiveness of catalytic performance. 展开更多
关键词 Platinum and palladium alloy nanoparticles Composition and size control Methanol oxidation
下载PDF
上一页 1 2 9 下一页 到第
使用帮助 返回顶部