检索结果-南通市图书馆

Comparative carbon emission assessments of recycled and natural aggregate concrete: Environmental influence of cement content

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Geoscience Frontiers 2021年第6期12卷 72-81页

作者： Marian Sab?u Dan V.Bompa Luis F.o.silva Department of Civil and Environmental Engineering Universidad de la Costa Department of Civil and Environmental Engineering University of Surrey Departamento de Ingeniería Civil y Arquitectura Universidad de Lima

This work examines the environmental and geochemical impact of recycled aggregate concrete production with properties representative for structural applications. The environmental influence of cement content, aggregate production, transportation, and waste landfilling is analysed by undertaking a life cycle assessment and considering a life cycle inventory largely specific for the region. To obtain a detailed insight into the optimum life cycle parameters, a sensitivity study is carried out in which supplementary cementitious materials, different values of natural-to-recycled aggregate content ratio and case-specific transportation distances were considered. The results show that carbon emissions were between 323 and 332 kg Co2e per cubic metre of cement only natural aggregate concrete. These values can be reduced by up to 17% by replacing 25% of the cement with fly ash. By contrast, carbon emissions can increase when natural coarse aggregates are replaced by recycled aggregates in proportions of 50% and 100%, and transportation is not included in analysis. However, the concrete with 50% recycled aggregate presented lower increase, only 0.3% and 3.4% for normal and high strength concrete, respectively. In some cases, the relative contribution of transportation to the total carbon emissions increased when cement was replaced by fly ash in proportions of 25%, and case-specific transportation distances were considered. In absolute values, the concrete mixes with 100% recycled aggregates and 25% fly ash had lower carbon emissions than concrete with cement and natural aggregates only. Higher environmental benefits can be obtained when the transportation distances of fly ash are relatively short(15–25 km) and the cement replacement by fly ash is equal or higher than 25%, considering that the mechanical properties are adequate for practical application. The observations from this paper show that recycled aggregate concrete with strength characteristics representative for s

关键词：

An efficient approach for anti-jamming in IRNSS receivers using improved PSo based parametric wavelet packet thresholding

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Satellite Navigation 2022年第3期3卷 51-70,I0003页

作者： Jacob silva Lorraine Kambham Madhu Ramarakula Department of ECE University College of EngineeringJNTUKKakinadaAndhra Pradesh533003India

The Indian Regional Navigation Satellite System provides accurate positioning service to the users within and around India,extending up to 1500 ***,when a receiver encounters a Continuous Wave Interference,its positioning accuracy degrades,or sometimes it even fails to *** Packet Transform(WPT)is the most widely used technique for anti-jamming in Global Navigation Satellite System *** the conventional method suffers from threshold drifting and employs inflexible thresholding ***,to address these issues,an efficient approach using Improved Particle Swarm optimization based Parametric Wavelet Packet Thresholding(IPSo-PWPT)is ***,a new parameter adaptive thresholding function is ***,a new form of inertia weight is presented to enhance the performance of ***,IPSo is used to optimize the key parameters of ***,the implementation of the IPSo-PWPT anti-jamming algorithm is *** performance of the proposed technique is evaluated for various performance metrics in four jamming *** evaluation results manifest the proposed method’s efficacy compared to the conventional WPT in terms of anti-jamming ***,the results show the ability of the new thresholding function to process various signals ***,the findings reveal that the improved PSo outperforms the variants of PSo.

关键词： Continuous wave interference(CWI) IRNSS Particle swarm optimization(PSo) Wavelet packet transform(WPT)

EDIToRIAL:Now is the Time for Energy Materials Research to Save the Planet

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Energy & Environmental Materials 2021年第4期4卷 497-499页

作者： S.Ravi P.silva Advanced Technology Institute University of SurreyGuildfordUK

Linking Energy Supply and Energy Storage to the UN Sustainable Development Goals our world has witnessed an unprecedented time in the last twelve months,with many activities coming to a standstill because of the CoVID-19 *** all walks of life,the world will not be the same as it struggles for normality at present,with many sectors shut for extended periods of time and some businesses shutdown for ***,with all this upheaval.

关键词： Sustainable shutdown struggle

维普期刊数据库

Antiglycation,antioxidant,antiacne,and photoprotective activities of crude extracts and triterpene saponin fraction of Sapindus saponaria ***:An in vitro study

在线全文

学校读者我要写书评

暂无评论

Asian Pacific Journal of Tropical Biomedicine 2022年第9期12卷 391-399页

作者： Regildo M.G.silva Gustavo R.Martins Laura M.B.Nucci Filipe o.Granero Célia C.M.Figueiredo Patrícia S.Santiago Luciana P.silva Laboratory of Herbal Medicine and Natural Products Department of BiotechnologyFaculty of SciencesHumanities and LanguagesSão Paulo State UniversityAssisSão PauloBrazil Institute of Chemistry São Paulo State UniversityAraraquaraSão PauloBrazil São Paulo State University Campus de RegistroRegistroSão PauloBrazil Fundação Educacional do Município de Assis AssisSão PauloBrazil

objective:To evaluate the photoprotective,antioxidant,antiglycation,and antiacne activities of crude extract(CESs)and triterpene saponin fraction(TSSs)of Sapindus ***:HPLC-MS purification was performed on a Symmetry TM C18 *** saponins were identified by a UV *** activity was evaluated by DPPH and o_(2)^(−)radicals scavenging,and FRAP and TBARS *** activity was assessed by relative electrophoretic mobility and inhibition of advanced glycation end products(AGEs)***,antiacne activity was determined by inhibition of Cutibacterium acnes,and photoprotective effect was evaluated by Mansur’s ***:Most of the triterpene saponins detected in the fraction by HPLC-MS analysis were hederagenin as the *** and TSSs presented varying antioxidant activity in DPPH(CESs:75.69%and TSSs:83.65%),FRAP(CESs:425.39μM TE/g DW and TSSs:649.36μM TE/g DW),TBARS(CESs:42.96%and TSSs:52.16%)and o_(2)^(−)radicals scavenging(CESs:61.33%and TSSs:86.69%)*** and TSSs also exhibited antiglycation activity comparable to bovine serum albumin treated with *** addition,CESs and TSSs showed inhibition of AGE formation(34.48%and 61.85%,respectively).Antiacne activity against Cutibacterium acnes was observed with a minimum inhibitory concentration equal to minimum bactericidal concentration(CESs:36.11µg/mL and TSSs:18.34µg/mL).In photoprotective assays,CESs and TSSs showed maximum absorbance of 1.42 to 0.20 and 2.80 to 1.30,respectively,in the wavelength range of 260 to 400 ***,CESs and TSSs showed sun protection factors of 8.89 and 14.89,***:Sapindus saponaria fruit extracts show strong antioxidant potential and antiglycation activity against bovine serum albumin glycation and AGE ***,they presented antibacterial activity against Cutibacterium acnes and photoprotective effect against UV-A and UV-B.

关键词： Photoprotective AGE formation Free radical Antioxidant Triterpene saponin Sapindus saponaria

Mechanical behavior of iron ore tailings under standard compression and extension triaxial stress paths

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 Rock Mechanics and Geotechnical Engineering 2023年第7期15卷 1883-1894页

作者： Alexia Cindy Wagner João Paulo de Sousa silva João Vítor de Azambuja Carvalho Ana Luisa Cezar Rissoli Pedro Pazzoto Cacciari Helder Mansur Chaves Hugo Carlos Scheuermann Filho Nilo Cesar Consoli Universidade Federal do Rio Grande do Sul Porto Alegre90035-190Brazil Mineral Development Centre Vale S.A.Santa Luzia33040-900Brazil Department of Civil Geological and Mining EngineeringPolytechnique MontrealMontrealH3C 3A7Canada

The disposal of mining tailings has increasingly focused on the use of dry *** structures offer more security since they use filtered and compacted *** of the construction method and the heights achieved,the material that compounds the structure can be subjected to different stress paths along the failure *** theoretical framework considered in the design of these structures generally is the critical state soil mechanics(CSSM).However,the data in the literature concerning the uniqueness of critical state line(CSL)is still controversial as the soil is subjected to different stress *** respect to tailings,this question is even more *** paper studies two tailings with different gradings due to the beneficial processes over extension and compression paths.A series of drained and undrained triaxial tests was conducted over a range of initial densities and stress *** the q-p'plane,different critical stress ratio(M)values were obtained for compression and extension stress ***,the critical state friction angle is very similar with a slightly higher critical state friction angle for extension *** stress path dependent CSLs were obtained in the n-lnp0 plane with the extension tests below the CSL defined in *** the fines content,the studied tailings presented very similar M and critical state friction angle ***,the fines content af-fects the volumetric behavior of the studied tailings and the CSLs on the n-lnp0 plane shift downwards with the increasing fines content for compression and extension *** relation to dilatancy analysis,the fines content did not present an evident influence on the dilatancy of the ***,different values of mean stress ratio N were obtained between compression and extension tests and can corroborate the existence of non-unique CSLs for these materials.

关键词： Iron ore tailings(IoTs) Dry stacking Critical state soil mechanics Extension tests Stress path

Impacts of land use and land cover changes on hydrological processes and sediment yield determined using the SWAT model

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2022年第1期37卷 54-69页

作者： Edivaldo Afonso de oliveira Serr?o Madson Tavares silva Thomás Rocha Ferreira Lorena Concei??o Paiva de Ataide Cleber Assis dos Santos Aline Maria Meiguins de Lima Vicente de Paulo Rodrigues da silva Francisco de Assis Salviano de Sousa Denis José Cardoso Gomes Academic Unit of Atmospheric Sciences Federal University of Campina Grande Department of Physics Center for Natural and Exact Sciences Federal University of Santa Maria Institute of Technology Civil Engineering Graduate Program Federal University of Pará Earth System Science Center National Institute of Space Research Institute of Geosciences Federal University of Pará

Land use and land cover (LULC) changes strongly affect local hydrology and sediment *** current study focused on a basin in the Brazilian Amazon and had the following three objectives:(1) to perform an effective diagnosis of flow and sediment yield,(2) to evaluate the impacts of LULC changes over the last 40 years on the hydro-sedimentological variables,and (3) to investigate the impacts of the possible trends or breaking points in the flow,surface runoff,and sediment yield *** Soil and Water Assessment Tool (SWAT) model validation showed that the simulated results were consistent with the data measured in the dynamic reproduction of flow ***,changes in LULC altered surface runoff,sediment yield,and flow according to the Mann-Kendall and Pettitt non-parametric *** was also observed that the sub-basins in which pastureland is predominant are more susceptible to increased surface runoff and sediment *** to trend and homogeneity tests,these sub-basins had break points in the time series of these *** the other hand,in the sub-basins whose land cover is predominantly forest,the time series is homogeneous and *** current study highlighted the impacts that 40 years of LULC changes in an Amazonian basin had on hydro-sedimentological variables,which,in turn,can play an important role in changing the hydrological cycle,consequently these changes can also impact diverse human activities in the region,such as agribusiness,livestock,energy production,food security,and public water ***,it is concluded that the SWAT model is a good estimator of hydro-sedimentological processes in Amazonian basins and can be used by decision makers in the management of water and environmental resources.

关键词： Hydrological modeling Sediment yield Amazon basin SWAT model

Assessment of hybrid geoids in Chile and Spain,combining GGM and GNSS/Leveling observations

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2021年第2期12卷 65-92页

作者： Jose Antonio Tarrio Mosquera Marcelo Caverlotti silva Fernando Isla Carlos Prado University of Santiago of Chile(USACH) Faculty of EngineeringGeographical Engineering DepartmentChile Geographic Military Institute Chile

This research presents the results for analyses done to five geopotential global models(GGM),comparing them with ground data from GNSS and leveling in heterogenic zones from the geodetic perspective,in Chile and *** the official and complete implementation of the International Height Reference Frame(IHRF)has not yet been established,the vertical geodetic system of many countries is not calculated on a global scale;instead,it is calculated by the variation of relative heights between one or more local tide gauges,such as in the case of Spain and *** aspect creates regional and specific altimetry data,which disables the use of GGM to directly obtain the orthometric height of the vertical reference system(VRS)from the GNSS *** models currently reach centimetric precision due to their high resolution but are directly incompatible for a local *** solve this,we expose in this article the contrast between geometric geoidal undulation(ellipsoidal heights and orthometric data from the leveling networks in Spain and Chile)with the geoidal undulation in more recent models and higher resolution:Earth Gravitational Model 2008(EGM08),European Improved Gravity model of the Earth by New techniques(EIGEN6 C4),Gravity observation Combination(GoCo05 C),Experimental Gravity Field Model(XGM2016),and Ultra-High Resolution Global Geopotential Model(SGG-UGM),adjusting the residual between both referential heights by different parametric models and polynomials of determined *** evaluated,their geoidal undulations are combined with GNSS/leveling data from the corresponding VRS to generate a correcting surface,which is also known as a hybrid geoid,resulting in a model of optimal adjustment for the combination of five parameters of the EIGEN-6 C4 with orthometric heights and ellipsoids of both Chile and *** results show 2-3 cm precisions,which were statistically analyzed to determine the suitability for *** final products are three grids of indep

关键词： GNSS levelling Correcting surface IHRS SIRGAS EIGEN-6C4

维普期刊数据库

Machine learning applied to road safety modeling:A systematic literature review

在线全文

学校读者我要写书评

暂无评论

Journal of Traffic and Transportation Engineering(English Edition) 2020年第6期7卷 775-790页

作者： Philippe Barbosa silva Michelle Andrade Sara Ferreira Department of Civil Engineering Goiano Federal Institute-Rio Verde CampusRio Verde 75901-970Brazil Department of Civil and Environmental Engineering University of BrasiliaBrasilia 70910-900Brazil Research Centre for Territory Transports and EnvironmentUniversity of PortoPorto 4200-465Portugal

Road safety modeling is a valuable strategy for promoting safe mobility,enabling the development of crash prediction models(CPM)and the investigation of factors contributing to crash *** modeling has traditionally used statistical techniques despite acknowledging the limitations of this kind of approach(specific assumptions and prior definition of the link functions),which provides an opportunity to explore alternatives such as the use of machine learning(ML)*** study reviews papers that used ML techniques for the development of CPM.A systematic literature review protocol was conducted,that resulted in the analysis of papers and their *** types of models were identified:crash frequency,crash classification by severity,and crash frequency and *** first is a regression problem,the second,a classificatory one and the third can be approached either as a combination of the preceding two or as a regression model for the expected number of crashes by severity *** main groups of techniques used for these purposes are nearest neighbor classification,decision trees,evolutionary algorithms,support-vector machine,and artificial neural *** last one is used in many kinds of approaches given the ability to deal with both regression and classification problems,and also multivariate response *** paper also presents the main performance metrics used to evaluate the models and compares the results,showing the clear superiority of the ML-based models over the statistical *** addition,it identifies the main explanatory variables used in the models,which shows the predominance of road-environmental aspects as the most important factors contributing to crash *** review fulfilled its objective,identifying the various approaches and the main research characteristics,limitations,and opportunities,and also highlighting the potential of the usage of ML in crash analyses.

关键词： Transportation engineering Road safety modeling Crash prediction Crash injury severity Machine learning Systematic literature review

维普期刊数据库

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2017年第2期11卷 307-319页

作者： Chuitian RoNG Yasin N. silva Chunqing LI School of Computer Science & Software Engineering Tianjin Polytechnic University Tianjin 300387 China School of Mathematical & Natural Sciences Arizona State University Tempe AZ 85281 USA

String similarity join is an essential operation of many applications that need to find all similar string pairs from two given collections. A quantitative way to determine whether two strings are similar is to compute their similarity based on a certain similarity function. The string pairs with similarity above a certain threshold are regarded as results. The current approach to solving the similarity join problem is to use a unique threshold value. There are, however, several scenarios that require the support of multiple thresholds, for instance, when the dataset includes strings of various lengths. In this scenario, longer string pairs typically tolerate much more typos than shorter ones. Therefore, we proposed a so- lution for string similarity joins that supports different simi- larity thresholds in a single operator. In order to support dif- ferent thresholds, we devised two novel indexing techniques： partition based indexing and similarity aware indexing. To utilize the new indices and improve the join performance, we proposed new filtering methods and index probing tech- niques. To the best of our knowledge, this is the first work that addresses this problem. Experimental results on real-world datasets show that our solution performs efficiently while pro- viding a more flexible threshold specification.

关键词： similarity join similarity aware index similarity thresholds