Avanti Publishers
Not a member yet
711 research outputs found
Sort by
Transport of Atrazine and Dicamba through Silt and Loam Soils
Get PDF The objectives of this research were to determine the role of preferential flow paths in the transport of atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine) and dicamba (3-6-dichloro-2-methoxybenzoic acid) through silt and loam soils overlying the High Plains aquifer in Nebraska. In a previous study, 3 of 6 study areas demonstrated high percentages of macropores; those three areas were used in this study for analysis of chemical transport. As a subsequent part of the study, 12 intact soil cores (30-cm diameter by 40-cm height), were excavated sequentially, two from each of the following depths: 0-40cm and 40-80cm. These cores were used to study preferential flow characteristics using dye staining and to determine hydraulic properties. Two undisturbed experimental field plots, each with a 3-m2 surface area, were installed in three study areas in Nebraska. Each was instrumented with suction lysimeters and tensiometers at depths of 10cm to 80cm in 10-cm increments. Additionally, each plot was planted with corn (Zea mays). A neutron probe access tube was installed in each plot to determine soil water content at 15-cm intervals. All plots were enclosed with a raised frame (of 8-cm height) to prevent surface runoff. All suction lysimeters were purged monthly for three months and were sampled immediately prior to pre-plant herbicide application to obtain background chemical concentrations. Atrazine and dicamba moved rapidly through the soil, but only after a heavy rainfall event, probably owing to the presence of preferential flow paths and lack of microbial degradation in these soil areas. Staining of laboratory cores showed a positive correlation between the percent area stained by depth and the subsequent breakthrough of Br- in the laboratory and leaching of field-applied herbicides owing to large rainfall events. Suction lysimeter samples in the field showed increases in concentrations of herbicides at depths where laboratory data indicated greater percentages of what appeared to be preferential flow paths. Concentrations of atrazine and dicamba exceeding 0.30 and 0.05µg m1-1 were observed at depths of 10-30cm and 50-70cm after two months following heavy rainfall events. It appears from the laboratory experiment that preferential flow paths were a significant factor in transport of atrazine and dicamba. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government or GNS
Permselective Membranes for Gas Processing Replacing the Conventional Methods
Get PDFMembrane technology has gained acceptance for gas separation and recovery as membranes are friendly to the environment and less expensive. Membranes are starting to play a great role in industries such as separation and production of gases, sweetening of natural gas, processing of biogas and syngas, and oil refineries. This article evaluates the replacement of the conventional methods for gas processing by perm selective membranes and also offers an overview of the membrane technology in current use for gas processing in industries
Mode-I Crack Problem in Generalized Thermo-microstretch with Harmonic Wave under Three Theories
Get PDFA general model of the equations of generalized thermo-microstretch for an infinite space weakened by a finite linear opening Mode-I crack are solving. The material is homogeneous isotropic elastic half space. The crack is subjected to prescribed temperature and stress distribution. The formulation is applied to generalized thermoelasticity theories, using mathematical analysis with the purview of the Lord-Åžhulman (LS involving one relaxation time) and Green-Lindsay (GL includes two relaxation times) theories with respect to the classical dynamical coupled theory (CD). The harmonic wave method has been used to getting the exact expression of Normal displacement, Normal stress force, couple stresses, microstress and temperature distribution. The variations of the considered fields with the horizontal distance are explained graphically. A comparison also is made between the three theories and for different depths
Detection of Subsurface Voids in Soil Media Using Seismic Wave Methods
Get PDF This research investigated the effect of anomalies such as voids on surface wave propagation. This was achieved by studying the signal simultaneously in both the time and frequency domains with the assistance of time-frequency plots generated by continuous wavelet transformation (CWT). The study also investigated the effects of different types of wavelets on CWT and developed a protocol for processing seismic wave data for void detection. For this purpose a numerical and experimental study was conducted and the data was studied in both the time and frequency domains in conjunction with time-frequency plots. The response of the soil media is presented in the time-frequency plots. The presence of void like anomalies disrupts the time-frequency plot features and introduces new features. These features have been used for cavity detection
The Tectonic Thinking and Strategies in Louis I. Kahn’s Art Museums
Get PDF Through the use of tectonic form to integrate natural lighting and modern mechanical services into his art museum designs, Louis Kahn was able to give full expression to the spatial poetics of his tectonic thinking. By making a comparative examination of the literature and illustrations and presenting 3D models, we examine how, in the process of giving shape to space, Kahn was able to make the most of the inherent qualities of his materials to integrate the mechanical services into his three museums designs—the Yale University Art Gallery (1951–53); the Kimbell Art Museum (1966–72); and the Yale Center for British Art (1969–74)—while also making ample use of natural lighting. We then go on to investigate why Kahn adopted a design concept which used tectonic form and natural lighting to give expression to the inherent spatial characteristics of a museum. The results indicate that the architectural principle of complying with the structural form and order were the main factors influencing Kahn’s approach to integrating the mechanical services and natural light into these three designs. It was also found that Kahn’s pioneering use of passive natural lighting has had a significant impact on subsequent museum designs
Drilling Technology for Deep and HPHT Containing Sour Gas well in the ChuanDongBei Field of China
Get PDFChuanDongBei Field of Sichuan Basin is a HPHT deep gas reservoir with multiple pressure systems, with maximum formation temperature up to 156 oC and pressure gradient of 1.86 at the depth of 6500m. Part of the well section contains more than 5% CO2 and near to 10% H2S, so drilling operation is extremely challenged. Firstly, this paper introduces drilling challenges such as lost circulation, severe caving-in, pipe sticking in upper section, sour gas corrosion problems, low penetration rate in the middle and deep section.
Secondly, a lot of available key drilling technologies are innovated and provided, including casing program optimization, air and nitrogen drilling to improve ROP, combination drilling with anti-HT motor and fit for purpose PDC bits, anti-HT mud along with losses prevention technologies such as MPD, anti-gas channeling and big temperature difference cementing slurry in the long interval, BOP and H2S sour gas monitoring system with emergency plan and some management advices for deep HTHP containing sour gas wells.
Finally, some unexpectable application results regarding these techniques to solve a series of drilling difficulties have been mentioned according to 40 wells cases. Take well LG01-XY as an example, which was improved average ROP to 6.4m/h, extended the footage to 1713m in one specialized bit with air hammer, reduced drilling period to 145days, reached “zero pollution, zero harm, zero accident†achievement during H2S interval, got premium cementing result and well bore qualify. So it could be used as a technical reference while drilling in deep HTHP containing sour gas wells in similar geologically complicated gas fields
Development of an Artificial Neural Network Based Model for Mimicking Combustion Tube Experiments for Heavy Oil Recovery
Get PDFOver the years, technologies for improved recovery of heavy oil have become an important part of the research efforts to meet the increasing demand for oil. Various methods are being developed for heavy oil recovery and among them in-situ combustion process has shown a good degree of potential in laboratory and pilot tests conducted in field. The in-situ combustion process needs to be studied further extensively because of the high degree of operational complexities involved in the process. Extensive laboratory studies have been conducted; however, a typical in-situ combustion tube experiment in the laboratory can be very costly in terms of its time, personnel and equipment requirements.This work aims at reducing the number of laboratory experiments by developing an artificial neural network (ANN) that has the ability of emulating in-situ combustion tube experiments. An intelligent database was generated using commercial software to train the network within the parametric ranges adapted from previous experimental work. The ANN model was used to predict the cumulative production of oil, water and gas, peak temperature attained, location and velocity of the combustion front in the numerical combustion experiments mimicking the physical experiments. The proposed ANN model can be used to focus towards designing the experimental program within a rather small range of parameter variations resulting in more economical and focused analysis. Therefore, our methodology provides a unique and novel approach to understand in-situ combustion experiment
Determination of Director Angle for Flow Aligning Nematic Liquid Crystals under Couette Geometry
Get PDFWe consider steady state flow of nematic liquid crystals in a Couette geometry driven by the relative rotation of the two concentric cylinders. We use the standard Ericksen-Leslie continuum model. The director, a unit vector, represents the average molecular orientation. We assume strong anchoring conditions at the walls of the flow which fixes the director orientation, and find an explicit expression of the director angle as a function of its distance from the common axis of the rotating cylinders
Validating a Model for Bluff-Body Burners Using the HM1 Turbulent Nonpremixed Flame
Get PDF We conducted computational fluid dynamics modeling of the bluff-body stabilized flame known as HM1, which was studied experimentally in detail at the University of Sydney to provide modelers with sufficient measurements to allow validation of their computational models. This benchmark flame is turbulent nonpremixed with a fuel-jet composed of 50% hydrogen and 50% methane by volume (hence the acronym HM) surrounded by a coflow of air, which is bounded by the walls of a wind tunnel. We successfully perfromed computational modeling of this flame, utilizing the published data about the problem settings and using a customized solver based on the open-source control-volume toolkit OpenFOAM. We describe the model settings and report the results of our predictions and show how they agree well with the measurements in terms of axial and radial profiles of miscellaneous flow variables. We conducted the simulation employing two meshes and obtained a reasonably mesh-idepenedent solution. The results suggest that the model can provide satisfactory results with as few as 10000 wedge-type computational cells. The model thus represents a free and fast computer tool to assist in the design of industrial bluff-body burners that possess similarity with the analyzed burner here
Thermal Conductivity of Aqueous Solvents Used in CO2 Capture
Get PDFThe growing CO2 concentration in the atmosphere forces researchers to work on improving existing carbon dioxide capture technologies. This technology is energy-intensive and consumes significant amount of heat for solvent regeneration. Thermal conductivity is a key property for the estimation of the heat required for solvents regeneration. Accordingly, in the present work thermal conductivity is measured for six aqueous solvent used for this purpose; monoethanolamine (MEA), diethanolamine (DEA), 2-amino-2methyl-1-propanol (AMP), sodium hydroxide (NaOH), potassium carbonate (K2CO3), and potassium glycinate (PG) aqueous solutions for mole fraction range from 0.00 to 0.0825. The measurements were carried out at constant temperature (294.82K) and pressure (102.02kPa). The total experimental standard uncertainty of thermal conductivity, pressure, temperature, and mole fraction measurements were estimated to be ± 0.001 Wm-1K-1, ± 0.02kPa, ± 0.1K, and ± 0.0002, respectively. The measured values of thermal conductivity were compared with data and correlations reported in the literature. The average absolute deviation between measured and calculated values from available correlation equations for the thermal conductivity was lease than 0.5%