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Articles 31 - 60 of 84
Full-Text Articles in Nanoscience and Nanotechnology
Transport Properties Of Nano-Silica Contained Self-Consolidating Concrete, Borhan Moradi
Transport Properties Of Nano-Silica Contained Self-Consolidating Concrete, Borhan Moradi
UNLV Theses, Dissertations, Professional Papers, and Capstones
In this research study, transport properties of various self-consolidating concretes (SCCs) containing nano-particles (SiO2) were investigated. Nano-silica replaced a portion of the cementitious materials at different replacement levels ranging from 1.5 to 7.5% by weight. For the purpose of this investigation, flow, bulk, and transport properties of SCCs were studied. The investigated transport properties were absorption, water penetration, rapid chloride permeability, capillary absorption, rapid migration, and chloride diffusion. Transport properties of nano-silica SCCs were also compared to those of equivalent silica fume (micro silica) contained concretes, as well as those of control mixture (concrete without nano or micro silica).
Test …
Selected Durability Studies Of Geopolymer Concrete With Respect To Carbonation, Elevated Temperature, And Microbial Induced Corrosion, Mohammad Sufian Badar
Selected Durability Studies Of Geopolymer Concrete With Respect To Carbonation, Elevated Temperature, And Microbial Induced Corrosion, Mohammad Sufian Badar
Doctoral Dissertations
This thesis reports a comprehensive study related to the experimental evaluation of carbonation in reinforced geopolymer concrete, the evaluation of geopolymer concretes at elevated temperature, and the resistance of geopolymer concrete to microbial induced corrosion (MIC).
Carbonation: Reinforced concretes, made of geopolymer, prepared from two class F fly ashes and one class C fly ash, were subjected to accelerated carbonation treatment for a period of 450 days. Electrochemical, microstructure and pore structure examinations were performed to evaluate the effect of corrosion caused due to carbonation. GPC specimens prepared from class F fly ash exhibited lower corrosion rates by a factor …
Crystalline Cellulose – Atomistic Modeling Toolkit, Mateo Gomez, Pablo Zavattieri Dr.
Crystalline Cellulose – Atomistic Modeling Toolkit, Mateo Gomez, Pablo Zavattieri Dr.
The Summer Undergraduate Research Fellowship (SURF) Symposium
Nature has created efficient strategies to make materials with hierarchical internal structure that often exhibit exceptional mechanical properties. One such example is found in cellulose, in fact it is eight times stronger than stainless steel and advantage is that cellulose incredibly cheap, because processing is obtained from purified wood pulp (it is environmental friendly). The most prevalent modeling technique to study the fundamental mechanical behavior of the crystalline cellulose has been Molecular Dynamics (MD). As a predictive tool, MD allows us to study the behavior of crystalline cellulose at the atomic level, and as such, it accurately predicts the crystalline …
Biodiesel Production From Waste Trying Oils Over Lime Catalysts, João F. Gomes
Biodiesel Production From Waste Trying Oils Over Lime Catalysts, João F. Gomes
João F Gomes
No abstract provided.
Monitoring Exposure To Airborne Ultrafine Particles In Lisbon, Portugal, João F. Gomes
Monitoring Exposure To Airborne Ultrafine Particles In Lisbon, Portugal, João F. Gomes
João F Gomes
No abstract provided.
Comparison Of Deposited Surface Area Of Airborne Ultrafine Particles Generated From Two Welding Processes, João F. Gomes
Comparison Of Deposited Surface Area Of Airborne Ultrafine Particles Generated From Two Welding Processes, João F. Gomes
João F Gomes
No abstract provided.
Determination Of Airborne Nanoparticles From Welding Operations, João F. Gomes
Determination Of Airborne Nanoparticles From Welding Operations, João F. Gomes
João F Gomes
The aim of this study is to assess the levels of airborne ultrafine particles emitted in welding processes (tungsten inert gas (TIG), metal active gas (MAG) of carbon steel and friction stir welding (FSW) of aluminium) in terms of deposited area in pulmonary alveolar tract using a Nanoparticle Surface Area Monitor (NSAM) analyzer. The obtained results showed the dependence from process parameters on emitted ultrafine particles and demonstrated the presence of ultrafine particles compared to background levels. Data indicated that the process that resulted in the lowest levels of alveolar deposited surface area (ADSA) was FSW, followed by TIG and …
Exposure To Airborne Ultrafine Particles From Cooking In Portuguese Homes, João F. Gomes
Exposure To Airborne Ultrafine Particles From Cooking In Portuguese Homes, João F. Gomes
João F Gomes
No abstract provided.
Assessment Of Exposure To Airborne Ultrafine Particles In The Urban Environment Of Lisbon, Portugal, João F. Gomes
Assessment Of Exposure To Airborne Ultrafine Particles In The Urban Environment Of Lisbon, Portugal, João F. Gomes
João F Gomes
The aim of this study was the assessment of exposure to ultrafine in the urban environment of Lisbon, Portugal, due to automobile traffic, and consisted of the determination of deposited alveolar surface area in an avenue leading to the town center during late spring. This study revealed differentiated patterns for weekdays and weekends, which could be related with the fluxes of automobile traffic. During a typical week, ultrafine particles alveolar deposited surface area varied between 35.0 and 89.2 mm2/cm3, which is comparable with levels reported for other towns such in Germany and the United States. These measurements were also complemented …
Study On The Use Of Mgal Hydrotalcites As Solid Heterogeneous Catalysts For Biodiesel Production, João F. Gomes
Study On The Use Of Mgal Hydrotalcites As Solid Heterogeneous Catalysts For Biodiesel Production, João F. Gomes
João F Gomes
This paper, reports experimental work on the use of new heterogeneous solid basic catalysts for biodiesel production: double oxides of Mg and Al, produced by calcination, at high temperature, of MgAl lamellar structures, the hydrotalcites (HT). The most suitable catalyst system studied are hydrotalcite Mg:Al 2:1 calcinated at 507 ºC and 700 ºC, leading to higher values of FAME also in the second reaction stage. One of the prepared catalysts resulted in 97.1 % Fatty acids methyl esters (FAME) in the 1st reaction step, 92.2 % FAME in the 2nd reaction step and 34 % FAME in the 3rd reaction …
Technical Note: Friction Factor Diagrams For Pipe Flow, Jim Mcgovern
Technical Note: Friction Factor Diagrams For Pipe Flow, Jim Mcgovern
Articles
This technical note describes diagrams of friction factor for pipe flow that have been prepared using, mainly, the equations that Lewis Moody used to prepare his famous diagram in 1944. The preparation of the new diagrams was prompted by the need for vector graphics versions that could be used for teaching purposes and that could be distributed freely to students and others under a Creative Commons Attribution-Share-Alike license. Using a structure very similar to that of Moody's diagram, variants with the Darcy friction factor and the Fanning friction factor have been prepared. In addition, variants have been prepared that include …
Notice On A Case Study On The Utilization Of Wind Energy Potential On A Remote And Isolated Small Wastewater Treatment Plant, João F. Gomes
Notice On A Case Study On The Utilization Of Wind Energy Potential On A Remote And Isolated Small Wastewater Treatment Plant, João F. Gomes
João F Gomes
Small wastewater treatment plants (WWTP) are frequently located, by necessity, in remote and isolated sites, which increases the difficulty of its energy supply. Some of them are located near the seaside, in environmental sensible zones, and due to tourism activity of these sites, seasonal effects related with population size fluctuation can occur, which can originate certain inefficiencies concerning WWTP design and energy supply. The objective of this paper is to describe a step by step procedure for evaluation of the wind potential of sites that are dependent of in-situ energy generation, as well as, a case study on the utilization …
Seismic Characterization Of Select Engineered Nanoparticles In Essentially Saturated Glass Beads, Mohamed Nihad Rajabdeen
Seismic Characterization Of Select Engineered Nanoparticles In Essentially Saturated Glass Beads, Mohamed Nihad Rajabdeen
UNLV Theses, Dissertations, Professional Papers, and Capstones
A laboratory testing apparatus was developed for the study of seismic body wave propagation through nanoparticles dispersed in pore fluid that is essentially saturating glass beads. First, the responses of water-saturated glass bead specimens were studied to establish baseline signatures. Then the seismic responses in the presence of engineered nanoparticles of various concentrations dispersed in the pore fluid of the specimen chamber were studied to observe variances from baseline.
The testing apparatus incorporates piezoceramic bender elements to actuate and receive seismic body waves through a cylindrical column filled with glass beads and back-saturated at ambient pressure with liquid. The system …
Study On The Glycerolysis Reaction Of High Free Fatty Acid Oils For Use As Biodiesel Feedstock, João F. Gomes
Study On The Glycerolysis Reaction Of High Free Fatty Acid Oils For Use As Biodiesel Feedstock, João F. Gomes
João F Gomes
Biodiesel is the main alternative to fossil diesel and it may be produced from different feedstocks such as semi-refined vegetable oils, waste frying oils or animal fats. However, these feedstocks usually contain significant amounts of free fatty acids (FFA) that make them inadequate for the direct base catalyzed transesterification reaction (where the FFA content should be lower than 4%). The present work describes a possible method for the pre-treatment of oils with high content of FFA (20 to 50%) by esterification with glycerol. In order to reduce the FFA content, the reaction between these FFA and an esterification agent is …
Design Of A New Test Chamber For Evaluation Of The Toxicity Of Rubber Infill, João F. Gomes
Design Of A New Test Chamber For Evaluation Of The Toxicity Of Rubber Infill, João F. Gomes
João F Gomes
A test chamber was projected and built (according to ISO 16000-9 Standard) to simulate atmospheric conditions experienced by rubber infill (when applied in synthetic turf pitches) and measure accurately the airborne emissions of pollutants such as dusts and volatile organic compounds (VOC), as well as pollutants present in leacheates. It should be pointed out that standard ISO 16000-9 is only concerned with the determination of the emission of VOC from building products and furnishing (not specific of synthetic turf materials), while other standards are concerned with the emission of leacheates only. This procedure is to be considered as a technical …
What Is A Chemical Engineer ?, João F. Gomes
On The Toxicological Effects Of Airborne Nanoparticles From Welding Processes, João F. Gomes
On The Toxicological Effects Of Airborne Nanoparticles From Welding Processes, João F. Gomes
João F Gomes
No abstract provided.
Halloysite Clay Nanotubes For Controlled Delivery Of Chemically Active Agents, Elshard Abdullayev
Halloysite Clay Nanotubes For Controlled Delivery Of Chemically Active Agents, Elshard Abdullayev
Doctoral Dissertations
In this work we explored the capabilities of halloysite nanotubes as capsules for encapsulation and controlled delivery of the chemically and biologically active substances. Halloysite is a two-layered aluminosilicate which has a predominantly hollow tubular structure in the submicron range and is chemically similar to kaolinite [1, 2].
In the first section of this work, we analyzed the structure of the halloysite nanotubes as well as its capability to encapsulate and deliver biologically and chemically active agents, similarities and differences between release characteristics of different agents and how these differences relate with their chemical structure. Models were used to describe …
Advances On The Development Of Novel Heterogeneous Catalysts For Transesterification Of Triglycerides In Biodiesel, João F. Gomes
Advances On The Development Of Novel Heterogeneous Catalysts For Transesterification Of Triglycerides In Biodiesel, João F. Gomes
João F Gomes
This paper describes experimental work done towards the search for more profitable and sustainable alternatives regarding biodiesel production, using heterogeneous catalysts instead of the conventional homogenous alkaline catalysts, such as NaOH, KOH or sodium methoxide, for the methanolysis reaction. This experimental work is a first stage on the development and optimization of new solid catalysts, able to produce biodiesel from vegetable oils. The heterogeneous catalytic process has many differences from the currently used in industry homogeneous process. The main advantage is that, it requires lower investment costs, since no need for separation steps of methanol/catalyst, biodiesel/catalyst and glycerine/catalyst. This work …
A Simulation Study On The Abatement Of Co2 Emissions By De-Absorption, João F. Gomes
A Simulation Study On The Abatement Of Co2 Emissions By De-Absorption, João F. Gomes
João F Gomes
Due to the adverse effect of CO2 from fossil fuel combustion on the earth’s ecosystems, the most cost effective method for CO2 capture is an important area of research. The predominant process for CO2 capture currently employed by industry is chemical absorption in amine solutions. A dynamic model for the de-absorption process was developed with Monoethanolamine (MEA) solution. Henry’s law was used for modeling the vapour phase equilibrium of the CO2, and fugacity ratios calculated by the Peng Robinson equation of state (EOS) were used for H2O, MEA, N2 and O2. Chemical reactions between CO2 and MEA were included in …
2009 Report Of Crerg Research Activities, João F. Gomes
2009 Report Of Crerg Research Activities, João F. Gomes
João F Gomes
No abstract provided.
Toxicological Assessment Of Coated Versus Uncoated Rubber Granulates Obtained From Used Tires For Use In Sport Facilities, João F. Gomes
Toxicological Assessment Of Coated Versus Uncoated Rubber Granulates Obtained From Used Tires For Use In Sport Facilities, João F. Gomes
João F Gomes
Reuse of tire crumb in sport facilities is currently a very cost-effective waste management measure. Considering that incorporation of the waste materials in artificial turf would be facilitated if the rubber materials were already colored green, coatings were specifically developed for this purpose. This paper presents an experimental toxicological and environmental assessment aimed at comparing the obtained emissions to the environment in terms of polycyclic aromatic hydrocarbons (PAHs), heavy metals, and ecotoxicity for coated and noncoated rubber granulates. This study is a comprehensive evaluation of the major potential critical factors related with the release of all of these classes of …
Endargement Of Undeveloped Areas Of Serbia By Forest Fires, João F. Gomes
Endargement Of Undeveloped Areas Of Serbia By Forest Fires, João F. Gomes
João F Gomes
Considering the significance of discovering the causes of forest fires, the hypothesis on the solar activity is presented (i.e. physical–chemical characteristics of the solar wind) as the possible cause of these natural disasters. The empirical confirmation of the mentioned hypothesis was disabled by the non existence of an adequate data base on the (regional) distribution of the number of fires and burned areas on the level of Serbia. Therefore an emphasis is put on theoretical explanations, but also on the characteristic situations in which there is an agreement between the processes occurring on the Sun and fire phenomena in the …
2008 Report Of Crerg Research Activities, João F. Gomes
2008 Report Of Crerg Research Activities, João F. Gomes
João F Gomes
No abstract provided.
Study Of A Nanoscale Water Cluster By Atomic Force Microscopy, Manhee Lee, Baekman Sung, Nicole N. Hashemi, Wonho Jhe
Study Of A Nanoscale Water Cluster By Atomic Force Microscopy, Manhee Lee, Baekman Sung, Nicole N. Hashemi, Wonho Jhe
Nastaran Hashemi
We present a novel method for investigating a nanometric cluster of water molecules, which includes the formation and manipulation of nanometric water, and the measurement of its mechanical properties. The atomic force microscope based on the quartz tuning-fork sensor is employed to form and manipulate the nanometric water, and the theoretical tool of amplitude-modulation atomic force microscopy is used to obtain the elasticity, viscosity and dissipation energy of it. With high vertical resolution less than [similar]0.1 nm and high force sensitivity of [similar]0.01 N m−1, this tool facilitates the stable formation and manipulation of a nano-water cluster ([similar]104 molecules) in …
Assessment Of The Impact Of The European Co2 Emissions Trading Scheme On The Portuguese Chemical Industry, João F. Gomes
Assessment Of The Impact Of The European Co2 Emissions Trading Scheme On The Portuguese Chemical Industry, João F. Gomes
João F Gomes
No abstract provided.
Estimating Local Greenhouse Gas Emissions - A Case Study On A Portuguese Municipality, João F. Gomes
Estimating Local Greenhouse Gas Emissions - A Case Study On A Portuguese Municipality, João F. Gomes
João F Gomes
This paper describes the study that led to the development of a carbon dioxide emissions matrix for the Oeiras municipality, one of the largest Portuguese municipalities, located in the metropolitan area of Lisbon. This matrix takes into account the Greenhouse Gases (GHG) Emissions, due an increase of electricity demand in buildings as well as solid and liquid wastes treatment, from the domestic and services sectors. Using emission factors that were calculated from the relationship between the electricity produced and amount of treated wastes, the GHG emissions in the Oeiras municipality, were estimated for a time series of 6 years (1998 …
Dynamic Simulation Of Co2 Absorption From Post Combustion Gases, João Gomes
Dynamic Simulation Of Co2 Absorption From Post Combustion Gases, João Gomes
João F Gomes
CO2 capture from combustion flue gases is currently an issue of main interest due to the high taxes being imposed on industrial companies as a measure to achieve CO2 emissions abatement. CO2 capture can be efficiently achieved by gas absorption using amines, namely Monoethanolamine (MEA). Based on henrys law, validated with previously published experimental work, this study considers the development of a dynamic model of an absorption column for post combustion CO2 capture. A dynamic model of the temperature swing de-absorption process was developed with the integration of both models for absorption and de-absorption (with the introduction of heat exchangers, …
Reflexions On The Use Of Renewable Power Sources And Nuclear Energy In Portugal, João F. Gomes
Reflexions On The Use Of Renewable Power Sources And Nuclear Energy In Portugal, João F. Gomes
João F Gomes
This paper analyses the current energy balance of Portugal, considering the actual sources which are mainly traditional fossil fuels, hydroelectric power and renewables. Other potential sources are discussed also and taken into consideration in view of the previewed evolution of the country in energetic terms. Among these, nuclear power, once regarded as an option, is now being re-considered. This paper also sums up the main issues to be considered in a future debate on the subject.
Emissions Of Polyciclic Aromatic Hidrocarbons And Polyciclic Carbonyl Bifenils From Electric Arc Furnaces, João F. Gomes
Emissions Of Polyciclic Aromatic Hidrocarbons And Polyciclic Carbonyl Bifenils From Electric Arc Furnaces, João F. Gomes
João F Gomes
This paper describes work done in order to determine the emissions of highly toxic organic micropollutants from electric arc furnaces used in the production of carbon steel from scrap. The study will be allowing to derive relationships between the levels of airborne micropollutants and the operational parameters of the production process so that an abatement of pollution could be achieved. By using the European standard method CEN 1948 for dioxin like compounds sampling and measurement, it was possible to determine the characteristic fingerprint of micropollutants such as polycyclic aromatic hydrocarbons (PAHs) and PCBs emitted by this particular stationary source.