检索结果-南通市图书馆

PYRIDINATION OF POLY(VINYL CHLORIDE) via A HOMOLYTIC PATHWAY

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2007年第3期25卷 297-302页

作者： sad Moulay Zakia Zeffouni Laboratoire de Chimie-Physique Moléculaire et Macromoléculaire Faculté des Sciences de l'Ingénieur Département de Chimie IndustrielleUniversité Sad Dahlab de BlidaRoute de SoumaB. P. 270Blida 09000Algeria

PVC was subjected to a chemical modification aiming at replacing the chlorine atoms by pyridine groups via a homolytic route. Pyridine groups were peculiarly affixed to the PVC matrix via a carbon-carbon bond rather than a carbonnitrogen one. PVC was first iodinated using the Conant-Finkelstein reaction, followed by the application of the homolytic conditions of Minisci to generate pyridinated PVC with a varying degree of substitution. The extent of substitution was not high; the reaction on 30% iodinated PVC afforded a degree of modification no greater than 3%.

关键词： Conditions of Minisci Iodinated PVC Pyridinated PVC

Changes in plant community diversity and aboveground biomass along with altitude within an alpine meadow on the Three-River source region

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2012年第27期57卷 3573-3577页

作者： sa WenJun AN LiZhe sa Wei Institute of Botany Science School of Life SciencesLanzhou UniversityLanzhou 730000China School of Life Science Qinghai UniversityXining 810008China

The grassland is an important component of terrestrial ecosystems and plays a significant role in biodiversity and ecosystem *** the present study,the changes of plant species diversity and aboveground biomass productivity were examined along with the altitude in natural alpine grassland in the source region of three rivers on the Qinghai-Tibetan *** experimental locations were selected with altitudes ranging from 3862 to 4450 m above sea level(a.s.l.).The results indicated that Kobresia pygmaea meadow,Kobresia humilis meadow and salix cupularis shrub meadow had higher indices of diversity and aboveground *** distribution of species diversity,richness and aboveground biomass showed similarly unimodal patterns across the altitude gradient with the highest indices appeared at mid-altitudes *** changing trend of species diversity,richness and evenness also showed significant unimodal patterns with total aboveground biomass,and the highest species diversity occurred at intermediate level of *** research would provide a valuable reference for the protection of grassland biodiversity and maintaining of the grazing ecosystem function in the source region of the Three Rivers.

关键词：植物群落多样性地上生物量海拔高度高寒草甸三江源地区植物物种多样性生态系统功能生物多样性

HALOMETHYLATION OF POLYSTYRENE AND SUBSEQUENT PYRIDINATION VIA A HOMOLYTIC PATHWAY

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2006年第6期24卷 627-635页

作者： sad Moulay Nadia Mehdi Laboratoire de Chimie-Physique Moléculaire et Macromoléculaire Faculté des Sciences de l'Ingénieur Departement de Chimie IndustrielleUniversité de BlidaRoute de SoumaB. P. 270Blida 09000Algeria

Chloromethylation of polystyrene （PS） with two different chloromethylating systems methylal/thionyl chloride and paraformaldehyde/trimethylchlorosilane was studied. Soluble chloromethylated polystyrene with a degree of substitution of 89% was obtained. The Conant-Finkelstein reaction on the chloromethylated PS afforded soluble iodomethylated polystyrene with a degree of substitution as high as 96%. The reaction conditions of Minisci were employed to radically pyridinate PS via its iodomethylated derivative. Polyelectrolytes were formed which could be converted to normal polymers by treatment with a 20% aqueous solution of NaOH.

关键词： Chloromethylated polystyrene Conditions of Minisci Iodomethylated polystyrene Pyridinated polystyrene.

Response of photosynthesis,growth,and acorn mass of pedunculate oak to diff erent levels of nitrogen in wet and dry growing seasons

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2023年第1期34卷 167-176页

作者： Krunoslav Sever saša Bogdan ŽeljkoŠkvorc Faculty of Forestry and Wood Technology University of ZagrebSvetošimunska 2510000 ZagrebCroatia

The objective was to examine the effects of optimal leaf nitrogen levels>2.0%and suboptimal levels<2.0%,nitrogen nutrition on net photo synthetic rate,stem diameter increment,height growth increment and acorn mass of ... 详细信息

The objective was to examine the effects of optimal leaf nitrogen levels>2.0%and suboptimal levelsgen nutrition on net photo synthetic rate,stem diameter increment,height growth increment and acorn mass of pedunculate oak during 2010 in the absence of drought stress and during 2011 under the impact of moderate drought *** to the results,moderate drought stress significantly reduced net photo synthetic rate,stem diameter increment and height growth increment,while acorn mass was not *** nitrogen nutrition significantly reduced the net photo synthetic rate and stem diameter increment only in the wet year,acorn mass in both wet and dry years,while height growth increment was not significantly reduced by suboptimal nitrogen nutrition in either *** results indicate that optimal nitrogen levels can stimulate photo synthetic rate and stem diameter increment of pedunculate oak only in the absence of moderate drought ***,the results show that moderate drought stress is a more dominant stressor for photosynthesis and growth of pedunculate oak than suboptimal nitrogen nutrition,while for acorn development,it is the more dominant stressor.

关键词： Quercus robur L. Drought stress Net photosynthic rate Stem diameter increment Height growth increment Acorn mass

Strip Casting of High Performance Structural Alloys

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2004年第Z2期22卷 78-84页

作者： S S Park J g lee Nack J Kim Center for Advanced Aerospace Materials Pohang University of Science and TechnologyPohang 790-784Korea Center for Advanced Aerospace MaterialsPohang University of Science and TechnologyPohang 790-784Korea Center for Advanced Aerospace MaterialsPohang University of Science and TechnologyPohang 790-784Korea

There exists a great need for the development of high performance alloys due to increasing demands for energy conservation and environmental protection. Application of strip casting shows a strong potential for the improvement of properties of existing alloys and also for the development of novel alloy systems with superior properties. The present paper reviews our Center's activities in the development of high performance alloys by strip casting. Examples include (1) Al alloys, (2) wrought Mg alloys, and (3) bulk metallic glass (BMg) alloys.

关键词： strip casting 6061 Al alloy AZ Mg alloy bulk metallic glass (BMg) alloy dispersion hardening

Ecoregional height-diameter models for Scots pine in Turkiye

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

Journal of Forestry Research 2024年第6期35卷 49-61页

作者： Fadime sağlam Oytun Emre sakici Department of Forest Engineering Faculty of ForestryKastamonu University37150 KastamonuTurkey

Ecoregion-based height-diameter models were developed in the present study for Scots pine(Pinus sylves-tris L.)stands in Turkiye and included several ecological factors derived from a pre-existing ecoregional classification *** data were obtained from 2831 sample trees in 292 sample *** generalized height–diameter models were developed,and the best model(HD10)was selected according to statistical ***,nonlinear mixed-effects modeling was applied to the best *** R2 for the generalized height‒diameter model(Richards function)modified by Sharma and Parton is 0.951,and the final model included number of trees,dominant height,and diameter at breast height,with a random parameter associated with each ecoregion attached to the inverse of the mean basal *** full model predictions using the nonlinear mixed-effects model and the reduced model(HD10)predictions were compared using the nonlinear sum of extra squares test,which revealed significant differences between ecore-gions;ecoregion-based height–diameter models were thus found to be suitable to *** addition,using these models in appropriate ecoregions was very important for achieving reliable predictions with low prediction errors.

关键词： Tree height Nonlinear mixed-effects modelling Nonlinear sum of extra squares method Ecoregion Scots pine

Practices of backuping homomorphically encrypted databases

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 Computer Science 2019年第2期13卷 220-230页

作者： sa WANg Yiwen SHAO Yungang BAO SKL Computer Architecture Institute of Computing Technology Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China

Ideal homomorphic encryption is theoretically achievable but impractical in reality due to tremendous computing overhead. Homomorphically encrypted databases, such as CryptDB, leverage replication with partially homomorphic encryption schemes to support different SQL queries over encrypted data directly. These databases reach a balance between security and efficiency, but incur considerable storage overhead, especially when making backups. Unfortunately, general data compression techniques relying on data similarity exhibit inefficiency on encrypted data. We present CryptZip, a backup and recovery system that could highly reduce the backup storage cost of encrypted databases. The key idea is to leverage the metadata information of encryption schemes and selectively backup one or several columns among semantically redundant columns. The experimental results show that CryptZip could reduce up to 90.5% backup storage cost on TPC-C benchmark.

关键词： homomorphic encryption security deduplication

Synthesis,Structures,and Fluorescence Property of a Novel Heterometallic Complex Constructed by Imidazole

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

Chinese Journal of Structural Chemistry 2020年第5期39卷 942-948页

作者： LI sa-Ying Department of Chemistry Chemical Engineering Shaanxi Xueqian Normal UniversityXi'an 710100China

A novel heterometallic complex constructed by imidazole ligand,CoZn(C3N2H3)4(1),has been synthesized under hydrothermal *** 1 was characterized by IR spectra,thermal analysis,powder X-ray diffraction and single-crystal X-ray ***-crystal X-ray diffraction studies reveals that compound 1 is in the tetragonal system,space group I41cd with a=23.4371(5),b=23.4371(5),c=12.4430(7)?,V=6834.9(4)?3,Z=16,C12H12CoN8Zn,Mr=392.60,Dc=1.526 g/cm^3,F(000)=3152,μ=2.381 mm–1,R=0.0323 and w R=*** CoZn(C3N2H3)4 is one-dimensional heterometallic molecular chains,which are further extended into a 3D open ***,the solid-state fluorescence property of the complex has also been investigated at room temperature.

关键词： heterometallic complex crystal structure fluorescence property

A location-based fog computing optimization of energy management in smart buildings:DEVS modeling and design of connected objects

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2023年第2期17卷 179-195页

作者： Abdelfettah MAATOUg ghalem BELALEM saïd MAHMOUDI Computer Science Department Faculty of Exact and Applied SciencesUniversity of Oran 1 Ahmed Ben BellaOran 31000Algeria Science and Technology Department Faculty of Science and TechnologyUniversity of TIARETTiaret 14000Algeria Computer Science Department Faculty of EngineeringUniversity of MonsMons 7000Belgium

Nowadays,smart buildings rely on Internet of things(loT)technology derived from the cloud and fog computing paradigms to coordinate and collaborate between connected *** is characterized by low latency with a wider spread and geographically distributed nodes to support mobility,real-time interaction,and location-based *** provide optimum quality of user life in moderm buildings,we rely on a holistic Framework,designed in a way that decreases latency and improves energy saving and services efficiency with different *** EVent system Specification(DEVS)is a formalism used to describe simulation models in a modular *** this work,the sub-models of connected objects in the building are accurately and independently designed,and after installing them together,we easily get an integrated model which is subject to the fog computing *** results show that this new approach significantly,improves energy efficiency of buildings and reduces ***,with DEVS,we can easily add or remove sub-models to or from the overall model,allowing us to continually improve our designs.

关键词： smart building energy consumption IoT fog computing Framework DEVS simulation models