检索结果-南通市图书馆

Computer modeling in Engineering & Sciences 2020年第5期123卷 571-602页

作者： j.Serrano-Arellano j.m.belman-flores I.Hernández-Pérez K.m.Aguilar-Castro E.V.macías-melo F.Elizalde-Blancas j.m.Riesco-Ávila F.j.García-Rodríguez Instituto Tecnológico Superior de Huichapan El SaucilloHuichapan42411México Universidad de Guanajuato Palo BlancoSalamanca36885México Universidad juárez Autónoma de Tabasco CunduacánTabasco86690México Instituto Tecnológico de Celaya Col.FovisssteCelaya38010México

In the present study,an analysis of the heat and mass transfer in a ventilated cavity in a warm climate zone was carried out to analyze,among others,the temperatures and percentage of relative humidity(RH).The governing equations of the mathematical model were solved through the finite volume *** used the k-εturbulence mode to find the results of the variables of interest in seven climate records on a given *** velocity of the inlet flow of the air-H2O mixture was varied through the Reynolds number(Re)from 500 to *** outdoor weather conditions considered were solar radiation,ambient temperature,and *** was found that at low velocities,flow recirculation was formed inside the cavity which increased the temperature and concentration of *** Re=5000 the flow is predominantly forced,which tends to set the values of temperature and RH as 20°C and 20%*** values of the RH increase in the afternoon hours when the solar radiation decreases to the value of ***,the mass transfer through the values of Sh is maintained with similar values in the seven weather *** was concluded that when air conditioning supplies air at speeds higher than 0.26 m/s at low temperatures it produces cooling with low RH,this causes discomfort,illness and/or discomfort to the users.

关键词： Heat transfer mass transfer solar radiation turbulence

Occurrence,leaching,and mobility of major and trace elements in a coal mining waste dump:The case of Douro Coalfield,Portugal

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 Geoscience 2021年第2期2卷 121-128页

作者： j.Ribeiro D.flores Department of Earth Sciences University of CoimbraRua Silvio Lima3030-790CoimbraPortugal Institute of Earth Sciences-Porto Pole Rua Do Campo Alegre 6874169-007PortoPortugal Environment and Spatial Planning Department of GeosciencesUniversity of PortoRua Do Campo Alegre 6874169-007PortoPortugal

The coal mining residues from past mining activities in the Douro Coalfield are emplaced in many dumps near the mining areas,causing substantial environmental *** study aims to contribute to the investigation of environmental impacts caused by the disposal of the residue in the Douro Coalfield through the determination of the geochemical composition of waste materials collected at 3 e 15 m depth,and of the water-leachable fraction produced by percolation in these materials inside the *** elements with higher concentration in the leachates are Ca,Cd,Co,mg,mn,Na,Ni,S,and Zn,indicating that they are the most easily leached and accessible elements for percolation and mobilization into the *** presence of these elements in the leachates is principally attributed to their occurrence as water-soluble ions in clays and sulphides affected by natural weathering conditions,which promotes their breakdown and occurrence as exchangeable *** leachates are classified as acid *** weathering and leaching in the Sao Pedro da Cova waste dump are the principal~paths for chemical elements to be percolated and mobilized to environment,posing risk to the soils,waters and ecosystems in the surrounding areas.

关键词： Coal mining Waste dump Water-soluble compound Hazardous element

Asphaltene Erosion Process in Air Plasma: Emission Spectroscopy and Surface Analysis for Air-Plasma Reactions

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Plasma Science and Technology 2012年第4期14卷 303-311页

作者： H.mARTINEZ O. flores j.C. POVEDA B. CAmPILLO Institute of Physical Sciences Autonomous National University of Mexico Chemistry Faculty Autonomous National University of Mexico

Optical emission spectroscopy （OES） was applied for plasma characterization during the erosion of asphaltene substrates. An amount of 100 mg of asphaltene was carefully applied to an electrode and exposed to air-plasma glow discharge at a pressure of 1.0 Torr. The plasma was generated in a stainless steel discharge chamber by an ac generator at a frequency of 60 Hz, output power of 50 W and a gas flow rate of 1.8 L/min. The electron temperature and ion density were estimated to be 2.15±0.11 eV and （1.24±0.05）× 10^16 m^-3, respectively, using a double Langmuir probe. OES was employed to observe the emission from the asphaltene exposed to air plasma. Both molecular band emission from N2, N2＋, OH, CH, NH, O2 as well as CN, and atomic light emission from V and Hγ were observed and used to monitor the evolution of asphaltene erosion. The asphaltene erosion was analyzed with the aid of a scanning electron microscope （SEm） equipped with an energy dispersive X-ray （EDX） detector. The EDX analysis showed that the time evolution of elements C, O, S and V were similar and the chemical composition of the exposed asphaltenes remained constant. Particle size evolution was measured, showing a maximum size of 2307 μm after 60 min. This behavior is most likely related to particle agglomeration as a function of time.

关键词： asphaltene erosion surface analysis optical emission spectroscopy pulsedplasma glow discharge

维普期刊数据库

A transition from a large open pit into a novel “macroblock variant” block caving geometry at Chuquicamata mine, Codelco Chile

在线全文

学校读者我要写书评

暂无评论

journal of Rock mechanics and Geotechnical Engineering 2019年第3期11卷 549-561页

作者： German flores Alex Catalan Newcrest mining Ltd. Melbourne3004Australia Codelco Chile Santiago8320000Chile

With a history of more than 100 years, Chuquicamata has become one of the largest open pits in the world. Its current depth of 1100 m, length of 4500 m and width of 3000 m, resulting in haulage distances of over 11,000 m from pit bottom to the processing plant or waste dumps, with waste/ore ratio greater than 4 and much lower grades, are effectively determining its profitable limit by the end of this decade. Currently, there are over 4300 mt of geological resources containing 0.7% of copper and 340 ppm (1 ppm = 1 g/t) of molybdenum below the final pit shell. The corresponding orebody geometry is 3000 m northsouth, 300-800 m eastwest and the drilling campaign suggested the existence of more than 900 m of mineable ore from the final pit bottom. This is in spite of the fact that the Chuquicamata orebody is still open at depth. The business case to continue with the mining of the Chuquicamata orebody is to change from the current large open pit to a novel macroblock variant block caving geometry. This requires a production rate of 140,000 t/d (50 mt per annum), with a continuous material handling system to achieve the 7-year ramp-up to full production. The resolution of a number of known technical, operational and logistical challenges outside current industry practises which Chuquicamata will face over its projected 40-year mine life is therefore essential. These challenges include simultaneous operations of open pit and underground macroblocks and from the initial lift to the second lift, rapid ramp-up and optimum sequencing of the planned macroblocks, early dilution from the west fault and late dilution from potential slope failures, and the potential for major operational hazards. An equally important issue to be addressed is cultural given that the mining history in the northern region of Chile, which includes Chuquicamata, is predominantly open pit. This paper presents a synopsis of the main challenges that the Chuquicamata underground project will face in order t

关键词： macroblock variant Block caving Cave propagation Early and late dilutions Intensive preconditioning Rib pillar West fault Ore buffer

维普期刊数据库

Nucleation and growth kinetics of La0.7Sr0.3Cr0.4mn0.6O3-δ SOFC perovskite:Symmetry alteration evolution induced by Cu2+ and Ni2+ impregnation

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:materials International 2016年第6期26卷 665-670页

作者： A.Concha-Balderrama G.Rojas-George j.Alvarado-flores H.Esparza-Ponce m.H.Bocanegra-Bernal A.Reyes-Rojas Centro de Investigación en materiales Avanzados S.C.(CImAV) Laboratorio Nacional de NanotecnologíaMiguel de Cervantes 120 Complejo Industrial ChihuahuaCd.de Chihuahua

La0.7Sr0.3Cr0.4mn0.6O3-δperovskite nanoparticles have been synthetized using an ethylene glycol modified solgel method and impregnated by Cu0.75Ni0.25nanoparticles. The phase transitions and nucleation kinetics were studied by time resolved x-ray diffraction, Rietveld, Raman spectroscopy and high resolution transmission electron microscopy. Findings have shown that, an atomic disorder dominates from room temperature to 400 °C. Nanoparticles with crystal size m start through nuclei formation of La0.7Sr0.3Cr0.4mn0.6O3-δand SrCrO4solid solutions with Pm3m cubic and P21/n monoclinic symmetry respectively in the range of 600–650 °C. Symmetry reduction from the Pm3m→R3c space group had been obtained at a lower temperature（750 °C） than those reported in the literature in oxygen atmosphere and it was confirmed by an octahedral distortion, which takes place in the crystallographic direction[221]/（122）. The johnson-mehl-Avrami model had described the whole process, where the existence of two phases was shown before it reached its complete D3d6point group symmetry.

关键词： Perovskite structure Sol-gel method Composite Kinetics Rietveld

Laparoscopic sleeve gastrectomy:more than a restrictive bariatric surgery procedure?

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

World journal of Gastroenterology 2015年第41期21卷 11804-11814页

作者： David Benaiges Antonio más-Lorenzo Albert Goday josé m Ramon juan j Chillarón juan Pedro-Botet juana A flores-Le Roux Department of Endocrinology and Nutrition Hospital del Mar Department of medicine Universitat Autònoma de Barcelona Institut Hospital del mar d’Investigacions mèdiques (ImIm) CiberOBN Instituto de Salud Carlos III Department of Gastrointestinal Surgery Hospital del Mar

Sleeve gastrectomy(SG) is a restrictive bariatric surgery technique that was first used as part of restrictive horizontal gastrectomy in the original Scopinaro type biliopancreatic diversion. Its good results as a single technique have led to a rise in its use, and it is currently the second most performed technique worldwide. SG achieves clearly better results than other restrictive techniques and is comparable in some aspects to the Roux-en-Y gastric bypass, the current gold standard in bariatric surgery. These benefits have been associated with different pathophysiologic mechanisms unrelated to weight loss such as increased gastric emptying and intestinal transit, and activation of hormonal mechanisms such as increased GLP-1 hormone and decreased ghrelin. The aim of this review was to highlight the salient aspects of SG regarding its historical evolution, pathophysiologic mechanisms, main results, clinical applications and perioperative complications.

关键词： Bariatric surgery Sleeve gastrectomy Severe obesit

A Numerical Study Comparing the Effect on Residual Stresses of Two Different Types of Projectiles During Shot Peening

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 2016年第3期51卷 203-215页

作者： j.Solórzano-López F.A.García-Pastor Angélica flores-Luna UNAm Facultad de QuímicaCiudad de MéxicoMéxico Cinvestav Unidad Saltillo CoahuilaMéxico TecNm Instituto Tecnológico de Tláhuac IIICiudad de MéxicoMéxico

Shot peening is a widely used technique to improve fatigue life in metallic *** processing technique introduces a subsurface compressive residual stress field through a plastic deformation of the surface caused by the impact of a large number of high-speed *** are a number of parameters that affect the residual stress field depth and *** effects of the impact angle,shot speed and shot geometry are currently being *** particular,substituting spherical cast shots by cylindrical cut wire shots is an attractive option,especially in terms of *** effect of shot geometry on residual stresses,however,needs to be further *** industrial-scale experimentation is costly and cumbersome,mathematical modeling offers a convenient alternative to carry out this type of *** present work shows a comparison between the residual stresses generated by the impact of spherical and cylindrical projectiles on a steel *** threedimensional model was developed using ABAQUS finite element commercial software(Release 6.12,Dassault Systémes,France).The results show that cylindrical shots generate residual stress fields t hat a re higher in magnitude than t hose generated by a spherical ***,the residual stress field of cylindrical shots impacting the surface at an oblique angle shows an important degree of *** effect is not found when spherical shots impact the surface at the same oblique angle.

关键词： Shot Peening Finite element method Residual Stresses

microwave-ultrasound assisted extraction of red corn pigments and their effect on chemical composition and tecno-functional properties

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Food Bioscience 2022年第6期50卷 1111-1119页

作者： j.D.Garcia-Ortiz A.C.flores-Gallegos j.A.Ascacio-Valdés C.m.López-Badillo S.D.Nery-flores S.C.Esparza-González R.Rodríguez-Herrera School of Chemistry Autonomous University of CoahuilaCampus SaltilloSaltilloCoahuila25280Mexico School of Dentistry Autonomous University of CoahuilaCampus SaltilloSaltilloCoahuila25125Mexico

Currently, there is a growing interest in obtaining natural pigments, without presenting a risk to health, as well as to the matrix and food safety. The objective of this study was to characterize grains with different shades of red color (High pigmentation maize = RA, medium pigmentation maize = Rm, and Low pigmentation maize = RB, reddish maize with white segments = VO and white maize control = SC). The physical properties (kernel weight, length, width, thickness, and grain and flour color), chemical composition (moisture, fat, protein, fiber, starch, ash, and minerals), and techno-functional properties (capacity of absorption of organic molecules (OmAC), swelling (CH), oil retention (CAAC), and water absorption (WAS)) variables were measured. Afterward, Rm was selected, and a pigment extraction (EAUm) was carried out using microwave-ultrasound equipment with different ratios of ethanol (0, 30, and 70%) and citric acid ratios (0 and 1%). The color and properties of the solid (starch, protein, fat, and their techno-functional properties) were determined in the aqueous phase and were compared with the properties prior to EAUm. The results indicated that the red grains have higher starch content (57.6%) and reddish colors, in addition, VO presented higher moisture (10.4%), fat (6.7%) and fiber (10.0%). The colors of the pigments obtained with EtOH (30 and 70%) show shades red and yellow. Finally, the EAUm decreased the fat content up to 57%, increased WAS and CAAC in the residual flour and generated changes in OmAC and CH, increasing in aqueous medium and reducing with EtOH.

关键词： Natural colorant Zea mays Green extraction Proximal analysis NIR Agronomic properties

mechanical and natural ventilation systems in a greenhouse designed using computational fluid dynamics

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 Agricultural and Biological Engineering 2014年第1期7卷 1-16页

作者： jorge flores-Velazquez juan I.montero Esteban j.Baeza juan C.Lopez mexican Institute of Water Technology.Paseo Cuauhnáhuac 8532 Col.ProgresoC.P.62550JiutepecMor.Mexico Institut de Recerca i Tecnologia Agroalimentàries 08348Cabrils(Barcelona)Spain IFAPA Centro La mojonera(junta de Andalucía) Camino San Nicolás 104745 La MojoneraAlmeríaSpain Fundación Cajamar.Estación Experimental“Las Palmerillas”Autovía del mediterráneo Km 416 704710El EjidoAlmeríaSpain

The aim of this study was to analyse air exchange and temperature distribution in a greenhouse with combined mechanical and natural ventilation and to design more efficient mechanical ventilation *** this purpose,a computational fluid dynamics(CFD)model of the greenhouse was *** configurations were considered:Configuration 1(mechanical ventilation and closed roof ventilators),Configurations 2 and 3(mechanical ventilation and roof ventilators open 30%and 100%,respectively).After validation,the CFD model was used to improve the design of the greenhouse mechanical ventilation system in each of the three configurations *** greenhouse lengths,28 m,50 m,75 m and 100 m,were used in the *** to fan ventilation only,roof ventilation improved the climate of fan-ventilated greenhouses in terms of the air exchange rate(22%)and climate uniformity because the internal air was mixed better than with mechanical ventilation *** the greenhouse length increased,more advantages were achieved with natural ventilation compared to mechanical *** most configurations,there was a strong linear correlation between temperature gradient and greenhouse *** greenhouse whose regression line had the steepest slope was the one with closed roof *** the fan capacity produced a general reduction in temperature,but the effect was less intense for the greenhouses with open roof *** to box inlet ventilators,an enlarged continuous inlet in the wall opposite the fans increased overall system performance because it eliminated backflow recirculation zones,which are prone to produce high temperatures.

关键词： greenhouse cooling fan ventilation roof ventilators combined ventilation

Effect of Cu-ZnO-Al_2O_3 supported on H-ferrierite on hydrocarbons formation from CO hydrogenation

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 Catalysis 2016年第3期37卷 378-388页

作者： j.H.flores m.E.H.maia da Costa m.I.Pais da Silva 里约热内卢天主教大学生物化学系里约热内卢天主教大学物理系

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.

关键词： methanol synthesis catalyst Low supersaturation precipitation High supersaturation precipitation Syngas Hydrotalcite Hydrocarbon Dimethyl ether

维普期刊数据库