bluuebunny/crossref_metadata_2025 huggingface dataset:
Determining Interwell Connectivity and Reservoir Complexity through Frac Pressure Hits and Production Interference Analysis
Authors: Sardinha Christopher , Petr Christopher , Lehmann Jurgen , Pyecroft James
Published: September 2014

This paper presents a process for analyzing production interference and interwell hydraulic fracturing pressure hits for multi-well horizontal pads in unconventional reservoirs. Ten wells with varied spacing in separate formations are evaluated. The analysis determines the degree of connectivity between the wells to help assess the extent and complexity of the stimulated network. Many of these connections persist through flowback and early production. The results of the study impact decisions regarding well spacing, injection rate, perforation design and frac order.

A prescriptive completions program enabled observation of pressure interactions between wells during multi-stage hydraulic fracturing. Wellhead pressures are continuously recorded during all completions and flowback operations. The rate of pressure buildup plus the magnitude and frequency of the inter-well hits are studied. Pressure hits are then compared with production interactions between wells. Connections are mapped to form a comprehensive image of the fracture network.

In the pad studied, all wells had multiple hits with varying degrees of communication across the fracture network. Observations confirm that fractures had significant vertical and lateral growth establishing a highly complex network. Interference analysis indicates the connections between wells often diminish over time. As a final validation, the high degree of interaction and fracture overlap are shown to be consistent with high-resolution microseismic observations.

Establishing the extent of the effective fracture network is fundamental to deciding design variables. Multi-variable pad designs and production results can only be deciphered when viewed in conjunction with fracture interactions. The process discussed provides a simple way to observe and understand these interactions.
Does a Multi-Entry, Multi-Stage Fracturing Sleeve System Improve Production in Bakken Shale Wells Over Other Completion Methods?
Authors: Wellhoefer Ben , Eis Andy , Gullickson Geoffrey
Published: September 2014

Shale and unconventional reservoir wells require multiple completion options be available so that the best one can be selected to maximize the stimulation influence potential, enable efficient operations, and increase production potential. Shale and unconventional reservoir continuous resource wells are typically drilled horizontally with the completion system run in the lateral section of the wellbore. The completion design must enable the hydraulic fracturing of multiple discreet treatment zones in the target interval to help ensure economical production. Traditionally, unconventional reservoir wells have been completed using a plug and perforate methodology. This completion uses wireline intervention to set composite fracturing plugs for stage isolation and to perforate individual stages. Due to inefficiencies with this type of completion design, single entry fracturing sleeve systems (SE FSS) completions have gained acceptance. SE FSS offer a single entry point per stage and remove the need for wireline intervention thereby increasing completion efficiency. Recently, multi-entry fracturing sleeve systems (ME FSS) completions have been deployed in unconventional reservoir stimulation operations. ME FSS completions also do not require wireline intervention, and allow for multiple entry points per stage to be simultaneously stimulated. Even though it is optimal for unconventional reservoir development to have several completion alternatives, evaluation of the best method can be challenging.

This paper will evaluate the three dominant and currently applied completion methods by comparing wells in the Middle Bakken continuous resource play which have utilized all identified systems. The paper will discuss each of the three completion methods (Plug-and-Perforate, SE FSS, ME FSS), the completion design, and fracturing operations that are executed. The paper will then illustrate production results from using all three of the completion methods. This data will be drawn from similar well designs for comparison purposes.

Assessment of viability and production efficiency of ME FSS completions against other completion methods is the primary focus. Results will be presented based on production outputs obtained after a qualified 180 day period. Conclusions will also highlight the potential efficiency gains of a ME FSS completion versus traditional methods.
Effects of Pore Confinement on Rate-Transient Analysis of Shale Gas Reservoirs
Authors: Qanbari F. , Haghshenas B. , Clarkson C. R.
Published: September 2014

It is common practice to use PVT data measured in laboratories (i.e. bulk fluid properties) for reservoir modeling and production data analysis purposes. However, theoretical studies have shown that fluid properties (including critical properties, phase behavior, viscosity, density, etc.) change under nano-scale confinement in shale reservoirs due to the abundance of interactions between the fluid molecules and the pore walls (pore proximity effects). In addition to these effects, in nanopores, an adsorbed layer can form which could cause changes in the apparent permeability to the free gas phase. The purpose of this study therefore is to incorporate the effects of pore proximity and adsorbed layer thickness changes into rate-transient analysis. The transient linear flow period in particular is studied for this purpose as it is often the dominant flow period in shale gas wells.

An iterative integral method is used to solve the nonlinear partial differential equation (PDE) for fluid flow in the presence of pore proximity effects and changing adsorbed layer thickness. Fluid properties (i.e. viscosity and density) under confinement are simulated using critical property adjustments and conventional fluid property correlations. The simplified local density model is used to estimate the thickness of the adsorbed layer, and this is coupled with an apparent permeability equation, which accounts for diffusion and slippage phenomena, to quantify permeability alteration in the presence of an adsorbed layer. Stress-sensitivity of permeability is also accounted for.

The results of our analysis using simulated data show that neglecting proximity effects in linear flow analysis leads to overestimation of the linear flow parameter ( i.e. xfki) in nanoporous shale reservoirs. This in turn could cause errors in the derivation of fracture half-length, if permeability is known, or vice-versa.

The new modified analytical rate-transient analysis tools and procedures provided in this work will lead to improved linear flow analysis, should pore proximity and confinement effects be important. In general, this method can be used for inclusion of different pressure-dependent fluid and rock properties and processes in the analysis of shale gas reservoirs.
Entering a Liquid-Rich Shale Play Near the Top of the Learning Curve: Early Quantification and Application of Development Best Practices
Authors: Braun D. , Powell B. , Guo R. , Morad K. , Flint D. , Dixon R. K.
Published: September 2014

Exploitation of unconventional resources is evolving rapidly. Case in point: liquid-rich shale (LRS) plays, once impermeable source rock, are now a prime target for unconventional exploration and development, with economic plays, such as the Eagle Ford, proving the potential. However, given complex and expensive completion, drilling and production operations combined with relatively low production rates and commodity prices, slim economic margins will likely prevail for the foreseeable future. Hence, the difference between economic success and failure could be the pace at which an economically robust development plan can be conceived, tested and implemented.

With this in mind, entry into new plays must rapidly and intelligently build on all unconventional best practices to-date – of which there is no shortage. Unfortunately, most are presented as rules-of-thumb, intuitive-but-unquantifiable or come with a long caveat list. Thus, the authors of this paper chose to quantify the credible ranges of several selected best practices based on the belief that there are only a handful of key engineering and geological levers that have step-change influence on production and cost (as opposed to optimizations). We have built an unconventional development workflow that identifies them, quantifies them, risks them and constructs full field development scenarios, which are economically evaluated and ranked, using only initial exploration data. Thus, even early appraisal wells can be planned to mitigate development risks and ensure the highest value geological and engineering data is collected early and used to steer timely development decisions.

The workflow is not novel, but at its core it accepts the inherent uncertainty of unconventional reservoirs and seeks to test end-member cases to drive decision making. This workflow was applied by Shell while planning the development of the Duvernay LRS play in Canada and will be described in that context. It consists of: Identifying the key, play specific development leversGathering and analyzing analogue play data on these leversConstructing individual well production profiles and economicsBuilding field development "end game" scenariosEvaluating full development economics to understand total project value and robustness
Sequenced Fracture Treatment Diversion Enhances Horizontal Well Completions in the Eagle Ford Shale
Authors: Viswanathan Anup , Watkins Hunter , Reese Jennifer , Corman Andrew , Sinosic Brian
Published: September 2014

With the boom of the oil and gas activities in south Texas, our understanding of completions and completion optimization of multistage horizontal wells has been greatly enhanced. Various multiple-stage isolation techniques are currently being utilized. The success of any horizontal shale well depends on contacting maximum reservoir rock, causing operators to reduce interval length which, in turn, increases drilling and completions cost.

To enable extending the interval length and increasing effectively stimulated rock volume, a new sequenced fracturing technique was developed and successfully tested. The technique relies on a novel fracturing fluid diversion blend delivered downhole at high concentration levels, which are achieved by using degradable fibers to stabilize fluid fronts and prevent slug dispersion when displaced. Thus, only a minor amount of material is used, and the pill is seamlessly integrated into a fracturing design and execution to divert stimulation fluids to under-stimulated regions of the wellbore. The material degrades completely after the fracturing treatment has been completed, leaving no residual formation or fracture conductivity damage.

The technique was first applied on several wells without extending stage spacing. The consistent results and diversion performance led to introducing the technique to wells with increased stage spacing, with the objective of achieving higher productivity and higher operations efficiency.

The early diagnostic data from wells completed with this technology demonstrate that diversion was achieved and reservoir contact improved. On wells with restricted internal diameter and long stage spacing, this technique was the only viable option to complete a section of the wellbore. Surveillance measurements indicate that the fracture treatment covered the interval as planned.
Assessing Soil Nitrogen Availability using Microdialysis‐Derived Diffusive Flux Measurements
Authors: Shaw R. , Williams A. P. , Jones D. L.
Published: September 2014

Microdialysis‐based soil sampling offers a potential alternative to traditional soil core extractions that better informs about the availability of nitrogen (N) for plant nutrition. This study compared soil N status, as estimated using 0.5 M K2SO4and distilled water extractions, with microdialysis‐derived diffusive flux measurements in eight grassland soils up an altitudinal gradient. Soil extracts and microdialysis samples were analyzed for plant‐available N: total free amino acids, NH4+, and NO3−. In terms of the percentage contribution that amino acids, NH4+, and NO3−made to total plant‐available N, the microdialysis‐derived diffusive flux measurements were most similar to distilled water extractions. However, the relative magnitude of the diffusive flux measurements did not always reflect the pool sizes as estimated by the soil extractions, which suggests that the availability of N to plants, via diffusion, may be decoupled from concentration in these soils. The potential and limitations of microdialysis sampling and the implications of the results for soil N management are discussed.
Factors Affecting Ammonia Loss from Pastures Fertilized with Broiler Litter
Authors: Cassity-Duffey Kate , Cabrera Miguel , Rema John , Calvert Vaughn
Published: September 2014

Broiler litter is commonly surface‐applied to pasture in the southeastern United States as a method of waste management and to provide an inexpensive source of plant nutrients, such as N. However, predicting plant available N derived from litter can be difficult due to losses through NH3volatilization. We conducted 11 field studies to determine overall NH3loss as affected by environmental variables and litter characteristics. Ammonia loss as a percentage of the applied total N (TN) ranged from 0.9 to 10.5% in eleven 28‐d studies conducted from April to November in 2011 and 2012. In two studies, a series of small rain events (2–5 mm) combined with elevated soil water content (WC) (>0.2 g H2O g soil−1) decreased overall NH3losses, potentially due to N movement into the soil. In the remaining nine studies, average vapor pressure (VP) and initial NH4–N plus uric acid‐N (ANUA) explained 79% of the variability in cumulative NH3loss over 28 d. Our data suggest that elevated concentrations of initial uric acid‐N and NH4–N, as well as, elevated VP increase NH3losses. The effect of elevated VP on NH3losses was attributed to the rewetting of the litter, which likely leads to increased N mineralization and NH4–N in solution. The statistical model developed may help estimate NH3losses from surface‐applied litter and increase the accuracy of estimating available N under field conditions.
Alteration of Biochar Carbon Chemistry during Soil Incubations: SR‐FTIR and NEXAFS Investigation
Authors: Mukome Fungai N. D. , Kilcoyne Arthur L. D. , Parikh Sanjai J.
Published: September 2014

Near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy and synchrotron radiation based Fourier‐transform infrared (SR‐FTIR) microspectroscopy were utilized to systematically study the aging of three biochars under similar controlled conditions by tracking changes in the C chemistry of biochar in the presence and absence of a Typic Xerorthent soil. By utilizing both NEXAFS and SR‐FTIR, differences in the initial biochar C functional group composition due to feedstock (aromatic C was greater in walnut shell biochar than softwood feedstock) and pyrolysis temperature (no long‐range‐ordered C in wood feedstock made at 410°C compared with 510°C) were confirmed. The data provided spectroscopic evidence corroborating both the conceptual biphasic model for biochar degradation and the power model of organic matter continuum mass loss as biochar ages due to a more labile aliphatic biochar portion and an aromatic portion that is oxidized more slowly. Incubations in the presence and absence of soil revealed a decrease in the ratio of the 287.6 eV peak (aliphatic C) relative to the 285.5 eV peak (aromatic C) during the incubations. Binding through functional groups present on the aged biochar surfaces (e.g., quinones, phenols, carbonyls) as well as the physical protection of the biochar by the soil appears to retard biochar surface decomposition. This study provides high‐resolution spectroscopic data on discrete points on the biochar in addition to interactions between the soil and the biochar under conditions of minimal sample disturbance and destruction that corroborates current biochar stability and turnover models.
Improved multiple-objective dynamic programming model for reservoir operation optimization
Authors: Zhao Tongtiegang , Zhao Jianshi
Published: September 2014

Reservoirs are usually designed and operated for multiple purposes, which makes the multiple-objective issue important in reservoir operation. Based on multiple-objective dynamic programming (MODP), this study proposes an improved multiple-objective DP (IMODP) algorithm for reservoir operation optimization, which can be used to solve multiple-objective optimization models regardless whether the curvatures of trade-offs among objectives are concave or not. MODP retains all the Pareto-optimal solutions through backward induction, resulting in the exponential increase of computational burden with the length of study horizon. To improve the computational efficiency, this study incorporates the ranking technique into MODP and proposes an efficient IMODP algorithm. We demonstrate the effectiveness of IMODP through a hypothetical test and a real-world case. The hypothetical test includes three cases in which the trade-offs between objectives are concave, convex, and neither concave nor convex. The results show that IMODP satisfactorily captures the Pareto front for all three cases. The real-world test focuses on hydropower and analyzes the trade-offs between total energy and firm energy for Danjiangkou Reservoir. IMODP efficiently identifies the Pareto-optimal solutions and the trade-offs among objectives.
Two-dimensional numerical modeling of wood transport
Authors: Ruiz-Villanueva Virginia , Bladé Ernest , Sánchez-Juny Martí , Marti-Cardona Belén , Díez-Herrero Andrés , Bodoque José María
Published: September 2014

The transport of wood material in rivers has been the subject of various studies in recent years. Most research has focused on the ecological and geomorphologic role of wood, its recruitment processes and spatial distribution in streams. In this study, we focused on wood transport dynamics, and we have developed a numerical model to simulate wood transport coupled with a two-dimensional (2D) hydrodynamic model. For this purpose, wood drag forces were incorporated as additional source terms into the shallow water equations, which are solved together with wood transport by using the finite volume method. This new tool has been implemented as a computational module into ‘Iber’, a 2D hydraulic simulation software. The new module analyzes the initial motion threshold of wood based on the balance of forces involved in the wood's movement, and computes the position and velocity of differently shaped logs using a kinematic approach. The method also considers the interaction between the logs themselves and between the logs and the channel walls or boundaries. Flume experiments were used in a straight channel with obstructions to validate the model's capacity to accurately reproduce the movement of floating logs.
A new hybrid algorithm for rainfall–runoff process modeling based on the wavelet transform and genetic fuzzy system
Authors: Nourani Vahid , Tahershamsi Ahmad , Abbaszadeh Peyman , Shahrabi Jamal , Hadavandi Esmaeil
Published: September 2014

In this paper, two hybrid artificial intelligence (AI) based models were introduced for rainfall–runoff modeling. In the first model, a genetic fuzzy system (GFS) was developed and evolved for the prediction of watersheds' runoff one time step ahead. In the second model, the wavelet-GFS (WGFS) model, wavelet transform was also used as a data pre-processing method prior to GFS modeling and in this way the main time series of two variables (rainfall and runoff) were decomposed into some multi-frequency time series by the wavelet transform. Then, the GFS was trained using the transformed time series, and finally the runoff discharge was predicted one time step ahead. In addition, to specify the capability and reliability of the proposed WGFS model, multi-step ahead runoff forecasting was also implemented for the watersheds. The obtained results through the application of the models for rainfall–runoff modeling of two distinct watersheds, located in Azerbaijan, Iran showed that the runoff could be better forecasted through the proposed WGFS model than other AI-based models in terms of determination coefficient and root mean squared error criteria in both training and verifying steps.
Hydrodynamic modelling of a regulated Mediterranean coastal lagoon, the Albufera of Valencia (Spain)
Authors: Alba Javier García , Gómez Aina G. , del Barrio Fernández Pilar , Gómez Andrés García , Álvarez Díaz César
Published: September 2014

Coastal lagoon hydrodynamics are strongly influenced by sea water exchange, especially when the connection between the lagoon and the sea is artificially regulated. These situations increase the complexity of the hydrodynamic regime, requiring the use of numerical models to understand their behaviour. Traditionally, one-dimensional models have been used, although in recent years, the development of two-dimensional shallow water models and advanced numerical techniques have increased notably. However, most of the existing bi-dimensional models consider the connection to the sea as a boundary condition, and they do not take into consideration the sea-lagoon exchange. In this paper, a fully two-dimensional hydrodynamic model of a heavily regulated coastal lagoon, which includes the artificial connection with the sea, is presented. The model allows the characterization of water level variation in the lagoon, taking into account the combined effect of different forcings. This model consists of two hydrodynamic modules: a long wave module (two-dimensional depth-averaged) which includes the analysis of a system of sluice gates, and a wind module (quasi three-dimensional). The model was successfully calibrated and validated with real data, showing its ability to accurately describe the hydraulic dynamics of regulated coastal lagoons.
Effects of ultraviolet light disinfection on tetracycline-resistant bacteria in wastewater effluents
Authors: Childress H. , Sullivan B. , Kaur J. , Karthikeyan R.
Published: September 2014

The ubiquitous use of antibiotics has led to an increasing number of antibiotic-resistant bacterial strains, including strains that are multidrug-resistant, pathogenic, or both. There is also evidence to suggest that antibiotic resistance genes (ARGs) spread to the environment, humans, and animals through wastewater effluents. The overall objective of this study was to investigate the effect of ultraviolet (UV) light disinfection on antibiotic-resistant bacteria. Wastewater effluent samples from a wastewater treatment plant (WWTP) in Texas were evaluated for differences in tetracycline-resistant bacteria before and after UV treatment. The effects of photoreactivation or dark repair on the reactivation of bacteria present in WWTP effluent after UV disinfection were also examined. Culture-based methods were used to characterize viable heterotrophic, tetracycline-resistant heterotrophic, Escherichia coli, and tetracycline-resistant E. coli bacteria present before and after UV treatment. UV disinfection was found to be as effective at reducing concentrations of resistant heterotrophs and E. coli, as it was at reducing total bacterial concentrations. The lowest survival ratio following UV disinfection was observed in tetracycline-resistant E. coli showing particular susceptibility to UV treatment. Photoreactivation and dark repair rates were found to be comparable to each other for all bacterial populations.
Microbial water quality communication: public and practitioner insights from British Columbia, Canada
Authors: Dunn G. , Henrich N. , Holmes B. , Harris L. , Prystajecky N.
Published: September 2014

This work examines the communication interactions of water suppliers and health authorities with the general public regarding microbial source water quality for recreational and drinking water. We compare current approaches to risk communication observable in British Columbia (BC), Canada, with best practices derived from the communications literature, finding significant gaps between theory and practice. By considering public views and government practices together, we identify key disconnects, leading to the conclusion that at present, neither the public's needs nor public health officials' goals are being met. We find: (1) there is a general lack of awareness and poor understanding by the public of microbial threats to water and the associated health implications; (2) the public often does not know where to find water quality information; (3) public information needs are not identified or met; (4) information sharing by authorities is predominantly one-way and reactive (crisis-oriented); and (5) the effectiveness of communications is not evaluated. There is a need for both improved public understanding of water quality-related risks, and new approaches to ensure information related to water quality reaches audiences. Overall, greater attention should be given to planning and goal setting related to microbial water risk communication.
Efficacy of arsenic filtration by Kanchan Arsenic Filter in Nepal
Authors: Singh Anjana , Smith Linda S. , Shrestha Shreekrishna , Maden Narendra
Published: September 2014

Groundwater arsenic contamination has caused a significant public health burden in lowland regions of Nepal. For arsenic mitigation purposes, the Kanchan Arsenic Filter (KAF) was developed and validated for use in 2003 after pilot studies showed its effectiveness in removing arsenic. However, its efficacy in field conditions operating for a long period has been scarcely observed. In this study, we observe the efficacy of KAFs running over 6 months in highly arsenic-affected households in Nawalparasi district. We assessed pair-wise arsenic concentrations of 62 randomly selected household tubewells before filtration and after filtration via KAFs. Of 62 tubewells, 41 had influent arsenic concentration exceeding the Nepal drinking water quality standard value (50 μg/L). Of the 41 tubewells having unsafe arsenic levels, KAFs reduced arsenic concentration to the safe level for only 22 tubewells, an efficacy of 54%. In conclusion, we did not find significantly high efficacy of KAFs in reducing unsafe influent arsenic level to the safe level under the in situ field conditions.
Influence of solar water disinfection on immunity against cholera – a review
Authors: Ssemakalu Cornelius Cano , Ubomba-Jaswa Eunice , Motaung Keolebogile Shirley , Pillay Michael
Published: September 2014

Cholera remains a problem in developing countries. This is attributed to the unavailability of proper water treatment, sanitary infrastructure and poor hygiene. As a consequence, countries facing cholera outbreaks rely on interventions such as the use of oral rehydration therapy and antibiotics to save lives. In addition to vaccination, the provision of chlorine tablets and hygiene sensitization drives have been used to prevent new cholera infections. The implementation of these interventions remains a challenge due to constraints associated with the cost, ease of use and technical knowhow. These challenges have been reduced through the use of solar water disinfection (SODIS). The success of SODIS in mitigating the risk associated with the consumption of waterborne pathogens has been associated with solar irradiation. This has prompted a lot of focus on the solar component for enhanced disinfection. However, the role played by the host immune system following the consumption of solar-irradiated water pathogens has not received any significant attention. The mode of inactivation resulting from the exposure of microbiologically contaminated water results in immunologically important microbial states as well as components. In this review, the possible influence that solar water disinfection may have on the immunity against cholera is discussed.
Effectiveness of selected wastewater treatment plants in Yemen for reduction of faecal indicators and pathogenic bacteria in secondary effluents and sludge
Authors: Al-Gheethi Adel A. S. , Abdul-Monem M. O. , AL-Zubeiry A. H. S. , Efaq A. N. , Shamar A. M. , Al-Amery Ramzy M. A.
Published: September 2014

The aim of this study was to evaluate the efficiency of wastewater treatment plants (WWTPs) in Yemen for reduction of faecal indicators and pathogenic bacteria in the secondary effluents and sludge. Hundred sixty bacterial isolates were obtained from 27 secondary effluents and sludge samples generated from Ibb wastewater treatment plant (IWWTP), Taiz wastewater treatment plant (TWWTP), Aden wastewater treatment plant (AWWTP1 and 2) and Sana'a wastewater treatment plant (SWWTP) in Republic of Yemen. Isolation of the bacteria was carried out by the direct plate method on the several selective media. The concentrations of faecal coliforms (FCs) were more than that recommended by World Health Organisation guidelines in all secondary effluents samples expect for those collected from TWWTP. FCs in the sludge from IWWTP and SWWTP were more than the standards limits recommended by United State Environmental Protection Agency (U. S. EPA) Class B, while sludge from AWWTP and TWWTP meet U. S. EPA standards limits Class A and class B, respectively. Among 160 bacterial isolates, E. coli was the most common (detected in 88.88% of the samples), followed by Streptococcus faecalis (70.37%), Klebsiella pneumonia (66.67%), Enterobacter aerogenes (59.23%), Salmonella typhi (33.33%), S. typhimurium and Shigella sonni (25.93% for each) and Yersinia pestis (22.22%). The sludge samples collected from IWWTP and TWWTP and stored for 24 weeks at room temperature (25 ± 2 °C) met the standards limits recommended by U.S. EPA, Class A.
Cost-effectiveness of membrane bioreactors treatment system for low-level phosphorus reduction from municipal wastewater
Authors: Young Thor , Smoot Sebastian , Peeters Jeff , Côté Pierre
Published: September 2014

Phosphorus removal from municipal wastewater is primarily accomplished through a combination of biological uptake and chemical precipitation. This study examines the capital and operating costs of four strategies for phosphorus removal: conventional activated sludge (CAS), CAS followed by sand filtration, CAS followed by membrane filtration, and membrane bioreactors (MBR).

The cost-effectiveness of these four strategies to achieve three target levels of effluent total phosphorus is contrasted: 2.0, 0.3, and 0.1 mg/L. The impact of simultaneously achieving biological nitrogen removal in the system to achieve 10 mg/L total nitrogen is also considered. This study, which is balanced carefully to try to ensure a ‘level playing field’, reveals that MBR facilities are cost-competitive with CAS facilities when tertiary media filtration or tertiary membrane filtration is required for achieving moderate to high levels of phosphorus removal, particularly when simultaneous nitrogen removal is required.
Clear-water local scour at wide piers in shallow-water flow
Authors: Ahmad N. , Mohamed T. , Ali F. H. , Yusuf B.
Published: September 2014

Laboratory data for local scour depth regarding the size of wide piers are presented. Clear water scour tests were performed for various pier widths (0.06, 0.076, 0.102, 0.14 and 0.165 m), two types of pier shapes (circular and rectangular) and two types of uniform cohesionless bed sediment (d50 = 0.23 and d50 = 0.80 mm). New data are presented and used to demonstrate the effects of pier width, pier shape and sediment size on scour depth. The influence of equilibrium time (te) on scouring processes is also discussed. Equilibrium scour depths were found to decrease with increasing values of b/d50. The temporal development of equilibrium local scour depth with new laboratory data is demonstrated for flow intensity V/Vc = 0.95. On the other hand, the results of scour mechanism have shown a significant relationship between normalized volume of scoured and deposited with pier width, b. The experimental data obtained in this study and data available from the literature for wide piers are used to evaluate predictions of existing methods.
Detection and removal of pathogenic norovirus employing tertiary treatment in wastewater and water treatment facilities
Authors: Fitzhenry K. , Barrett M. , O'Flaherty V. , Dore W. , Keaveney S. , Cormican M. , Clifford E.
Published: September 2014

Human pathogenic viruses (HPVs) with particular reference to norovirus (NoV) commonly known as ‘the winter vomiting bug’ is the leading causes of viral gastroenteritis worldwide. NoV is present in wastewater in high numbers and coupled with a low infectious dose can endanger public health. Secondary wastewater treatment processes are not designed to eradicate HPVs thus a tertiary disinfection step is required. Typical pathogen removal processes include slow sand filtration and membrane barrier methods. NoV cannot be cultured in a laboratory and so its sole detection is limited to expensive and time-consuming molecular methods. The use of an alternative virus, the FRNA bacteriophages has been suggested as a surrogate for NoV due to its physicochemical similarities and cultivability. This research focuses on the investigation of a barrier method of tertiary disinfection using membrane filters and tangential flow filtration. In addition to this, the suitability of FRNA bacteriophages as a cheaper alternative indicator of NoV was investigated.
Socio-economic activities around Alau Dam and the quality of raw water supply to Maiduguri Treatment Plant, Nigeria
Authors: Dammo M. N. , Sangodoyin A. Y.
Published: September 2014

Water quality and supply are central to the socio-economic development of any nation. Scarcity of potable water results in the construction of dams and water treatment plants. Unfortunately, provision of potable water through improvement and treatment may prove to be difficult because of the socio-economic activities around a dam. This study is aimed at assessing the socio-economic activities around the Alau Dam Maiduguri, and how they affect the quality of raw water supply to Maiduguri Water Treatment Plant. The data was generated through the administration of questionnaires, and by interview and water quality analysis of dam and irrigation sites. The samples were subjected to physical, chemical and biological analysis to assess the impact of socio economic activities on the dam water, and its suitabilityfor drinking and agricultural uses. Findings reveal pollution with high concentration of nitrate (260–230 mg-NO3/l), phosphate (22–28 mg/l) and Escherichia coli (13–24 n/100 mg). This arose from improper sanitary management, inadequate public education on irrigation,indiscriminate waste disposaland some farming practices. Regular monitoring of socio-economic activities around the dam, and doing away with unhealthy waste disposal practices are recommended to safeguard the raw water supply to the treatment plant.
The Effect of Digital Games and Game Strategies on Young Adolescents' Aggression
Authors: Eden Sigal , Eshet-Alkalai Yoram
Published: September 2014

Violence is a major element in many of the present-day's digital games. Despite the extensive research on this subject, the effect of violent digital games on the aggression level among children has not been satisfactorily clarified. The study examines the combined effect of collaborative/competitive game strategy and the presence or absence of violence in the game on the aggression of young adolescents. Fifty-six young adolescents (28 girls, 28 boys) aged 10–13 years old participated in this study. They played digital games and answered questionnaires designed to check the influence of the game on their aggression level immediately after the game. Findings indicate that game strategy may have a significant effect on aggression level: collaborative game strategy was found to repress aggression, whereas competitive strategy was found to raise aggression levels among all subjects. The very existence of violence in the game was not found to be responsible for the aggression level of players. No differences in player aggression levels were found between genders.
Exploring E-Learning Acceptance among University Students in Thailand: A National Survey
Authors: Teo Timothy , Ruangrit Nammon , Khlaisang Jintavee , Thammetar Thapanee , Sunphakitjumnong Kobkul
Published: September 2014

This study surveys the e-learning acceptance of university students in Thailand. One thousand nine hundred and eighty-one (1,981) participants completed the E-Learning Acceptance Measure (Teo, 2010) which measures three constructs that predict e-learning acceptance (tutor quality, perceived usefulness, and facilitating conditions). Data analysis was performed using structural equation modeling (SEM). The results of this study showed that the three constructs were significant predictors of e-learning acceptance. Further analysis with MIMIC (multiple indicators, multiple causes) modeling revealed that university students' e-learning acceptance was significantly different by age and perceived technology competence. Younger students and those who perceived themselves to be technologically more competent reported a higher level of e-learning acceptance than older students and those who perceived themselves as less competent in using technology.
Put Your Robot in, Put Your Robot out: Sequencing through Programming Robots in Early Childhood
Authors: Kazakoff Elizabeth R. , Bers Marina Umaschi
Published: September 2014

This article examines the impact of programming robots on sequencing ability in early childhood. Thirty-four children (ages 4.5–6.5 years) participated in computer programming activities with a developmentally appropriate tool, CHERP, specifically designed to program a robot's behaviors. The children learned to build and program robots over three sessions, of 1.5 hours duration each, in a laboratory setting. The participants' sequencing skills were assessed before and after the intervention using a picture-story sequencing task. Pre- and post-test scores were compared using a paired sample t-test. A significant increase in post-test scores compared to pre-test scores was found.
Investor Heterogeneity, Auditor Choice, and Information Signaling
Authors: Wei Xu , Xiao Xiao , Zhou Yi
Published: September 2014

We develop a model of firms' auditor choices when presented with a heterogeneous group of investors. We show that firms' auditor choices in equilibrium depend on the composition of investors in the market. The signaling effect of choosing a high-quality auditor exists only when there is at least a certain proportion of sophisticated investors. If there is a sufficiently high proportion of sophisticated investors, then all firms will choose high-quality auditors. We also show that the overall audit quality in the market increases with an increasing proportion of sophisticated investors. When the audit market is differentiated and investors are heterogeneous, an increase in the penalty for firms that receive a qualified opinion will lead to a decrease in the overall audit quality in the market. Our conclusions remain valid even after taking audit fees, auditor quality change, and firm heterogeneity into consideration.
Use of contrast-enhanced ultrasonography to characterize adrenal gland tumors in dogs
Authors: Pey Pascaline , Rossi Federica , Vignoli Massimo , Duchateau Luc , Marescaux Laurent , Saunders Jimmy H.
Published: September 2014

Objective—To describe the contrast-enhanced ultrasonographic characteristics and vascular patterns of adrenal gland tumors in dogs and determine whether those features are indicative of malignancy or histologic type of tumor.

Animals—14 dogs with 16 adrenal gland lesions (10 carcinomas [8 dogs], 3 adenomas [3 dogs], and 3 pheochromocytomas [3 dogs]).

Procedures—Unsedated dogs with adrenal gland lesions underwent B-mode ultrasonography and contrast-enhanced ultrasonography ≤ 48 hours before adrenalectomy; contrast-enhanced ultrasonographic examinations were video-recorded. Macroscopic evaluation of the adrenal gland lesions and histologic examination of removed adrenal gland tissues were subsequently performed. Surgical and histopathologic findings and the ultrasonographic and contrast-enhanced ultrasonographic characteristics were recorded for the various tumor types. Time-intensity curves were generated from the contrast-enhanced ultrasonographic recordings and used to calculate regional blood volume (value proportional to area under the curve) and mean transit time (time the lesion began to enhance to the half-peak intensity).

Results—In adrenal gland carcinomas, tortuous feeding vessels were noticeable during the arterial and venous phases of contrast enhancement. Heterogeneity of contrast enhancement was evident only in malignant tumors. Compared with adenomas, adrenal gland carcinomas and pheochromocytomas had significantly less regional blood volume. Mean transit times were significantly shorter in adrenal gland carcinomas and pheochromocytomas than in adenomas.

Conclusions and Clinical Relevance—For dogs, evaluation of the vascular pattern and contrast-enhancement characteristics of adrenal gland tumors by means of contrast-enhanced ultrasonography may be useful in assessment of malignancy and tumor type.
Comparison of echocardiographic measurements in elite and nonelite Arabian endurance horses
Authors: Sleeper Meg M. , Durando Mary M. , Holbrook Todd C. , Payton Mark E. , Birks Eric K.
Published: September 2014

Objective—To determine whether echocardiographic variables differed between successful (elite) and less successful (nonelite) Arabian endurance horses.

Animals—34 Arabian horses that competed in endurance racing.

Procedures—Horses were assigned to either an elite or nonelite group on the basis of results of a previous competition, and a standardized echocardiographic examination was performed on each horse within 1 to 4 weeks after that competition. Multivariable logistic regression with backward stepwise elimination was used to create a prediction model for the determination of horse status (elite or nonelite) as a function of the measured echocardiographic variables.

Results—The elite and nonelite groups consisted of 23 and 11 horses, respectively. One horse in the nonelite group had a frequent ventricular dysrhythmia that could have negatively affected its performance and rider's safety, whereas none of the horses in the elite group had remarkable cardiac abnormalities. The left ventricular internal diameter during systole and diastole and left ventricular mass and stroke volume were significantly greater for horses in the elite group, compared with those for horses in the nonelite group. The final logistic regression model correctly predicted the horse status for all of the horses in the elite group and 8 of 11 horses in the nonelite group.

Conclusions and Clinical Relevance—Results indicated that heart size was significantly associated with performance for Arabian endurance horses in a manner similar to findings for Thoroughbred and Standardbred racehorses in active competition.
‘Crows’ vs. ‘Avatar,’ or: 3D vs. Total-Dimension Immersion
Authors: Martins José Manuel
Published: September 2014

3D film’s explicit new space depth arguably provides both an enhanced realistic quality to the image and a wealth of more acute visual and haptic sensations (a ‘montage of attractions’) to the increasingly involved spectator. But David Cronenberg’s related ironic remark that “cinema as such is from the outset a ‘special effect’” should warn us against the geometrical naiveté of such assumptions, within a Cartesian ocularcentric tradition for long overcome by Merleau-Ponty’s embodiment of perception and Deleuze’s notion of the self-consistency of the artistic sensation and space. Indeed, ‘2D’ traditional cinema already provides the accomplished “fourth wall effect,” enclosing the beholder behind his back within a space that no longer belongs to the screen (nor to ‘reality’) as such, and therefore is no longer ‘illusorily’ two-dimensional. This kind of totally absorbing, ‘dream-like’ space, metaphorical for both painting and cinema, is illustrated by the episode Crows in Kurosawa’s Dreams (1990). Such a space requires the actual effacement of the empirical status of spectator, screen, and film as separate dimensions, and it is precisely the 3D characteristic unfolding of merely frontal space layers (and film events) out of the screen towards us (and sometimes above the heads of the spectators before us) that reinstalls at the core of the film-viewing phenomenon a regressive struggle with reality and with different degrees of realism, originally overcome by film since the Lumière’s Arrival of a Train at Ciotat (L’Arrivée d’un train en gare de la Ciotat, 1896) seminal demonstration. Through an analysis of crucial aspects in Avatar (James Cameron, 2009) and the recent Cave of Forgotten Dreams (Werner Herzog, 2010), both dealing with historical and ontological deepening processes of ‘going inside,’ we shall try to show how the formal and technically advanced component of those 3D-depth films impairs, on the contrary, their apparent conceptual purpose on the level of contents, and we will assume, drawing on Merleau-Ponty and Deleuze, that this technological mistake is due to a lack of recognition of the nature of perception and sensation in relation to space and human experience.
A simple method for mapping woody plant cover in agricultural fields using airborne lidar / Lihtne meetod aerolidari andmete põhjal puitttaimestiku kaardistamiseks mahajäetud põllumaadel
Authors: Lang Mait
Published: September 2014

Information about the status of agricultural land is of strategic interest in every country. In Estonia, different and even contradicting estimates of area of actively used as agricultural land exist. To solve this problem, airborne laser scanning (ALS) data can be used to map the woody plant cover (values range from 0 to 1 corresponding to the no cover and full tree canopy cover) in agricultural land and to provide digital maps for further analysis. Canopy cover was estimated from ALS data by setting reference height to 2 m from ground. Validation dataset was created from ortophotos on 442 rectangular 100 m2 elementary sampling units. The relationship was linear and determination coefficient was high (R2 = 0.795) and the model fitting residual standard error was 0.116 indicating good applicability of ALS for woody plant cover mapping. The method can be easily automated, does not require additional fieldwork and can be applied in all places where ALS data are available
Assessment of NTSG MODIS NPP product for forests in Kurzeme region, Latvia / Kuramaa metsade primaarproduktsiooni hindamisest NTSG MODIS NPP andmestiku abil
Authors: Lang Mait , Traškovs Agris , Gulbe Linda
Published: September 2014

The space-borne Moderate Resolution Imaging Spectroradiometer (MODIS) data based net primary production (NPP) product from Numerical Terradynamic Simulation Group (NTSG) was tested in the Kurzeme region, Latvia using a stand-wise forest inventory database. The NPP product has been validated globally and found to have no overall bias. In this study the NPP product was compared with stem biomass increment and soil fertility in respect to distance from the Baltic Sea coast. For each MODIS NPP product pixel we calculated forest cover, share of coniferous trees, average stem biomass increment and average site fertility (growth potential estimate). Then, 2432 pixels with a forest cover over 75% were selected for analysis. The results indicated that MODIS NPP decreased with distance from Baltic Sea coast but stem biomass increment and site fertility indicated a trend of increase. There was no functional relationship between MODIS NPP and stem biomass increment. Analysis of the landcover map used by NTSG for MODIS NPP product showed that the classes “Evergreen needleleaf” and “Mixed forests” differentiated only 10% by mode value of coniferous proportions in species composition. A non-natural jump was detected in the MODIS NPP values at a longitude of 22.5 degrees east corresponding to the border of the coarse scale meteorological dataset (NCEP Reanalysis (R2)) data representation unit. According to the results the MODIS NPP product is not applicable for regional level planning but can probably provide only rough average estimates of NPP for the Baltic region