bluuebunny/crossref_metadata_2025 huggingface dataset:
An Updated Fractional Flow Model of Low Salinity Water Flooding with Respect to the Impact of Salt Diffusion
Authors: Al-Ibadi Hasan , Stephen Karl , Mackay Eric
Published: June 2018

Low Salinity Water Flooding (LSWF) is an emergent technology developed to increase oil recovery. Many laboratory tests of LSWF have been carried out since the 1990's, but modelling at the reservoir scale is less well reported. Various descriptions of the functional relationship between salt concentration and relative permeability have been presented in the literature, as have the differences in the effective salinity range over which salt content takes effect. This paper focuses on these properties and their impact on the fractional flow of LSWF. We present observations that help characterise the flow behaviour in a more general form, simplifying the interpretation of results. We explain how numerical or physical diffusion of salt affects the velocity of the waterflood front, and how this can be predicted from fractional flow analysis.

We have considered various linear and non-linear shapes of the function relating salinity to relative permeability and different effective salinity ranges using a numerical simulator applied at the reservoir scale. The results are compared to fractional flow theory in which both salt and water movement is assumed to be shock-like in nature.

We observe that diffusion of the salt front is an important process that affects the fractional flow behaviour depending on the effective salinity range. The simulator solution matches the analytical predictions from fractional flow analysis under the condition that the mid-point of the effective salinity range is at the mid-point between the formation and injected salt concentrations. However, an effective behaviour similar to adsorption/desorption occurs when these mid-point concentrations are not coincidental. The outcome is that the fronts representing high and low salinity water travel with altered velocities and at different saturations.

We find that we can predict this behaviour from the input data alone as an augmented form of the fractional flow theory including the concept of retardation or acceleration as occurs for adsorption and desorption for other injectants. We use the analytical solution to the advection-diffusion equation and find that the changes in behaviour depends on the Peclet number.

The result of our work is that we have produced an updated form of the fractional flow model of LSWF, to include the impact of salt front diffusion on the movement of fluids. A new factor is introduced, similar to adsorption in polymer flooding. We have developed a new mathematical formula, empirically, to estimate the magnitude of this factor. The new form can be used to modify the effects that numerical or physical diffusion have on the breakthrough times of high and low salinity water fronts during LSFW. This will improve predictive ability and also reduce the requirement for full simulation.
Estimation of OGIP in a Water-Drive Gas Reservoir Coupling Dynamic Material Balance and Fetkovich Aquifer Model
Authors: Zavaleta S. , Adrian P. M. , Michel Michel
Published: June 2018

Although various novel techniques were developed in reservoir engineering for estimation of hydrocarbons initially in place (HCIIP), conventional material balance still remains as one of the most reliable. Average reservoir pressure is critical input data for material balance, which is usually obtained by well shut-in. Nevertheless, this operation might be restricted due to economic and operational restrictions such as water production in gas wells.

In contrast, daily production data is commonly available and can be used to calculate the HCIIP by applying any production data analysis techniques such as the Dynamic Material Balance (DMB) method. The application of such methods to volumetric gas reservoirs and naturally fractured reservoirs resulted in accurate and reliable estimations. However, for water drive gas reservoirs, where the water influx term should be introduced into the iterative process, research and field case applications are limited.

This paper presents an extension to the DMB technique to water-drive gas reservoirs. A simultaneous estimation of the Original Gas-in-place (OGIP) and the water influx term is achieved by coupling the DMB technique with the Fetkovich aquifer model. Average reservoir pressure estimation can also be attained as a result of the coupled method.

Results were validated by means of numerical simulation on a synthetic model and a field study case. Synthetic production data was generated by a commercial simulator and then analized with the coupled method. The calculated OGIP, water influx volumes and average reservoir pressure resulted comparable to simulator output as they presented a low relative error. Furthermore, application of the coupled method to the field study case yielded comparable results to those obtained by volumetric method.
The Faults in our Fields – Well Count and Placement in a Columbus Basin Gas Field
Authors: Dowlath Joel , Onyeagoro Kachi , Sookal Elizabeth , Quammie Kevan , Srinivasan Ashwin
Published: June 2018

The Enterprise gas field is a discovery in Shell's operated acreage in the Columbus Basin off the east coast of Trinidad. It is comprised of two major fault blocks, with an exploration well in the smaller one and an appraisal well in the larger one. The larger fault block is further broken up by minor faults. The potential compartmentalization of this fault block is the major uncertainty in the development of the Enterprise field.

The development plan called for one or two wells to be drilled in the Enterprise field. Detailed mapping of each of the minor faults and analysis of log and pressure data from the wells was used to determine how well connected the various segments are. Using relationships derived from a global database and Vshale logs from offset wells, a range of fault transmissibility multipliers was derived for each fault based on calculated shale gouge ratios and mapped fault throws.

Results of the dynamic fault seal analysis were integrated with dynamic simulation and showed that using base case fault transmissibility multipliers, for all segments where there is reservoir-reservoir juxtaposition across the minor faults, there will be connectivity and the larger fault block can be drained by a single development well. Various combinations of well placements were tested against low, base and high case geological realizations and these were used to determine the optimal development scenario for the field.
Integrated Sand Control Method Design Based on Dsa, Lpsa and Geologic Aspects
Authors: Peña Gerado , Chaparro Humberto , Rodriguez Inti , Azuaje Evelyn
Published: June 2018

Design a completion system for sand control based on top technology as an alternative to the slotted-liner completions systems currently installed in extra heavy oil producing wells in unconsolidated formations.

The methodology and design are based on the resulting interpretations of Dry Sieve Analysis (DSA), Laser Particle Sieve Analysis (LPSA), and geological considerations. Based on the results of these analyses, uniformity coefficients were calculated and grain size sorting results were used to validate the completion criteria, the system type, and the open area to be used. Once these criterions were selected, the Sand Retention Test (SRT) was utilized in the laboratory to verify the performance of the design using different liner sections and core plugs specific to the area; which allowed the selection of the appropriate system. Quantifying the total recovered barrels with the new completion system was done using a nodal analysis in order to evaluate the cost benefit in a typical well.

As result of the interpretations of the tests, it was determined that the open area size of the completion system should be 200 μm, being estimated by the D10 obtained by the DSA realized to the core "A" of the Lower Morichal Formation. With the LPSA realized to the core "B", the quantity of thin grain movables less than 45 μm was estimated for the Lower Morichal Formation. All of these criteria were unified to select the completion method best suited for sand control. The results shows that the best option is metal mesh screen, which offer 150% more flow area in comparison with the slotted liner which translates to a recovery of 10% in production according to nodal analysis simulations.

While current design practices sometimes take into consideration grain size distribution and sorting, this paper highlights the added benefit of combining this approach with the laboratory results of the DSA and LPSA testing methods to ensure that production recovery is truly maximized.
A Study in Quantifying Thin-Bedded Pay Contribution Within a Deltaic System in the Columbus Basin
Authors: Fortune Jochelle , Jackman Randell
Published: June 2018

The objective of this study was to systematically and quantitatively quantify where production from Thin – Bedded Pay may be more challenging using conventional methods of completion. This study will focus on different areas within the deltaic environment in which Thin – Bedded Pay are prominent. A 3D structural model was built and populated with properties to represent four (4) different main classes of geological environments with a deltaic system. It explored the effect of completing across the conventional sands only vs completing both the conventional and secondary units. The main finding in this thesis is that completing the thin-bedded pay increased the overall rate of the production on average of about 10% in different environments. In addition, in complicated reservoir architecture environments such as the upper slope and distal delta slope environments, there are significant (14% and 10%) incremental increases in the recovery factors by completing across these thinly bedded zones. Thus, it is recommended that these environments be further explored in how best to develop the thin-bedded resource in these environments since, in a time when the finite resources of oil and gas are becoming scarce, it is important to understand what reserves we may have that are not currently being tapped into.
Application of the Capacitance Model in Primary Production Period before IOR Implementation
Authors: Soroush Mohammad , Rasaei Mohammad Reza
Published: June 2018

Injection and production historical data are easily accessible and using them does not incur the costs of running field tests. The capacitance model (CM), an analytical model based on injection and production data, has recently been applied successfully in several field cases. The CM has two outcomes, rate prediction and well to well connectivity evaluation and primarily derived for waterflood period. This paper modified this model for primary production period.

The CM has been developed from linear productivity model and material balance equation and predicts the total production rate of each producer as a function of the injection rates of all injectors in the system and the bottomhole pressures (BHPs) of all producers. In this paper the CM is modified based on two methods, Pseudo Injectors and BHP methods. Pseudo Injectors method is used for well to well connectivity assessment and BHP method is used for production prediction.

The modified CM was applied for several synthetic field examples and one Iranian oil reservoir. The results of synthetic fields showed that the modified CM can assess the interwell connectivity, reservoir heterogeneity, strength of aquifer, and wellbore productivity in primary production period. In addition, the modified CM can predict production rate and determine suitable areas of future IOR application. The results of modified CM on Iranian field assessed the effect of aquifer in the area and evaluated the degree of heterogeneity of the sands around the producers.

Unlike simulation-based methods, the CM does not require geological and geophysical data to generate the initial model. Developed modified CM can be applied before IOR implementation to assess reservoir continuity and manage future IOR strategies such as well pattern and amount of injected fluid.
A Practical Method for Estimating Stimulated Reservoir Volume in Shale Gas Reservoirs: Coupling Knudsen Diffusion and Surface Diffusion
Authors: Miao Yanan , Lee John , Zhao Chaojie , Lin Wenji , Li Han , Chang Yucui , Zhou Yunjian , Li Xiangfang
Published: June 2018

Estimating stimulated reservoir volume (SRV) in shale gas reservoirs with high accuracy has been of more concern to oil and gas industries. However, current SRV prediction methods are of limited use for characterizing critical flow mechanisms. To make more accurate prediction of SRV in shale gas reservoirs, multiple mechanisms cannot be ignored. In this paper, we develop a novel analytical model to accurately estimate the volume of SRV in shale gas reserviors by incorporating both Knudsen diffusion of bulk gas and surface diffusion of adsorbed gas directly into the model. Depending on flow discrepancies from conventional reservoirs, the modified pseudo-pressure equation to account for these critical transport mechanisms are further constructed. Predicted values of SRV by using this new model are in fair agreement with values from the CMG simulation. Compared with related research, it is the first time that both Knudsen diffusion of bulk gas and surface diffusion of adsorbed gas are taken into consdertion to analyze and estimate the volume of SRV in shale gas reservoirs. A clear workflow for implementation of this method is presented. Compared with the common numerical reservoir simulators, this approach is easier to setup and less data-intensive.
Adapting Fiscal Regimes to Entice Operators to Implement EOR Schemes
Authors: Nunez Fernando , Ramirez Christian Alan , Bashbush Jose Luis , Espinola Oswaldo
Published: June 2018

To optimize profit from Oil and Gas production activities, the Operating companies are often constrained in one side by contract terms with the host governments and on the other side by the nature of the reservoir, its fluids, and the resulting economics associated to its production and development. Enhanced Oil Recovery (EOR) methodologies have shown to provide satisfactory results in increasing the recovery factor. Nonetheless, their applications are normally linked to important capital investments which might turn the economics of the project not favorable, unless enticements are offered to ease the way towards a win-win pre-arrangement.

This paper aims to contrast results from economic evaluations and assessments for the implementation of an EOR methodology in a type field and how to foster cooperation with regulatory bodies to adapt their fiscal conditions to stimulate implementation of EOR techniques. In that way the host country could benefit from higher investment, larger production, increased tax revenue and a better recovery factors while the operating company would be enticed to assemble a quality team to design viable alternatives to maximize recoveries, increase reserves while increasing their profitability.

The methodology proposed considers the calculation of economic and business indicators such as: Net Present Value, Internal Rate of Return, Payout time, Company take and Government take which are obtained considering typical fiscal regimes applicable for Enhanced Oil Recovery techniques as a function of production profiles and EOR methodologies. The analyses are benchmarked versus natural depletion of current development, comparing investment alternatives and technical and economic benefits of possible Enhanced Oil Recovery alternatives and their prudent implementation.

The implementation of EOR techniques for different fields are either incentivized or discouraged as a function of the different terms of typical fiscal regimes for hydrocarbon production. A proper analysis of the alternatives could be used as the basis of negotiations for the fiscal regime configuration to be applied. Provided the regulations are already intelligently designed and properly approved. Various production scenarios are analyzed to ascertain which EOR methodology may be more advantageous from the points of view of operating companies, national oil companies and government take.
A Numerical Model for Pressure Transient Analysis in Fractured Reservoirs with Poorly Connected Fractures
Authors: Chu Hongyang , Liao Xinwei , Chen Zhiming , He Youwei , Zou Jiandong , Zhang Jiali , Zhao Juan , Wei Jiaxin
Published: June 2018

Given that some fractured reservoirs have poorly connected natural fractures, the conventional Warren and Root model (1963) may not applicable. To narrow this gap, we introduce a numerical method to build a dual-porosity model for those reservoirs. To verify this numerical model, we perform a case study with a semianalytical model (SPE-187290-MS) for a discretely fractured reservoir. During the model verification, the pressure response from this numerical model are compared to the semianalytical results for fractured reservoirs with poorly connected fractures. It is found that the difference between the pressure responses obtained by these two models is negligible. Results show that pressure transient behaviors of wells with intersecting fracture exhibit completely different flow regimes with those without intersecting fracture. Bilinear flow, linear flow, transient flow, and pseudo-radial flow may progressively occur for intersecting fracture. A radial flow in matrix occurs for discrete fractures, before the impacts of nature fractures exhibit. Once these impacts are detected, the pressure derivatives show a dual-porosity feature "V-shape", which is virtually quite different from that in Warren and Root's dual-porosity model.
Stability Improvement of CO2 Foam for Enhanced Oil Recovery Applications Using Nanoparticles and Viscoelastic Surfactants
Authors: Farid Ibrahim Ahmed , Nasr-El-Din Hisham
Published: June 2018

CO2-enhanced oil recovery (EOR) was started in 1950. Low sweep efficiency and early breakthrough issues were associated with the CO2-EOR system. Foam-EOR was introduced to improve the sweep efficiency instead of polymers to avoid formation damage caused by polymers. Foam stability reduces in high-salinity environments, high-temperature formations (>212°F), and in contact with crude oil. The present study the using of nanoparticles and viscoelastic surfactants (VES) to improve foam mobility control for EOR application.

This paper study the CO2-foam stability with using alpha olefin sulfonate (AOS) as a foaming agent and the change on the mobility-reduction factor (MRF) for different foam solutions by adding nanoparticles and VES. To achieve this objective, foam-stability for different solutions was measured at 77 and 150°F using high-pressure view chamber (HPVC). Interfacial tension measurements were conducted to investigate the destabilizing effect of crude oil on the different foam systems. Coreflood experiments were conducted using Buff Berea sandstone cores at 150°F, saturated initially with a dead-crude oil. The CO2 foam was injected with 80% quality as tertiary recovery mode. The oil recovery and the pressure drop across the core were measured for the different foam solutions.

Adding silica nanoparticles (0.1 wt%) of size 140 nm and viscoelastic cocamidopropyl betaine surfactant (cocobetaine VES) (0.4 wt%) to the AOS (0.5 wt%) solution improves both foam stability and MRF. In contact with crude oil, unstable oil-in-water emulsion formed inside the foam lamella that decreased foam stability. A weak foam was formed for AOS solution, but the foam stability increased by adding nanoparticles and VES. The interfacial tension measurements revealed positive values for the spreading and the bridging coefficients. Hence, the crude oil spread over the gas-water interface, and lamella films were unstable due to the bridging of oil droplets. The oil recovery from the conventional waterflooding (as a secondary recovery before foam injection) was 48% of the original oil-in-place. From the series coreflood experiments, AOS was not able to enhance the oil recovery. However, more oil was recovered in the presence of nanoparticles (12 %) and VES (18%).

Nanoparticles and VES were able to improve the foam stability for AOS solution. Adding nanoparticles is highly recommended for EOR applications, particularly at high temperatures.
Application of Integrated Dynamic Asset Modeling to Predict and Resolve Production Instabilities in an Offshore Facility, A Case Study, Mexico
Authors: Espinola Oswaldo , Mehranfar Reza , Alvarez Julieta , Villanueva Julio , Vazquez Laura
Published: June 2018

Integrated asset modeling has been used for the last decade with a wide technical application covering different challenges from field development to production optimization. Besides supporting the FEEDS and FEL studies for different purposes. Moreover, the technology has evolved in terms of integration and dynamic or transient simulation has been added as an extra element expanding the possibility to cover different challenges and workflows. The objective of this paper is to show how this dynamic integration (Dynamic integrated asset modeling) was applied to a common problem of several reservoirs that produce water and gas under different dynamic mechanisms (injection, aquifer and gas cap) to understand, from the reservoir perspective, the effects of gas and water conning over the entire production system.

The methodology applied was using a refined sector model solved with numerical simulation and coupled with a transient multiphase flow simulator to see how pressure drop affect the contacts level and shape based on the petrophysical properties and under different production scenarios and generate different graphics to see how this phenomenon behaves. Besides a comparison with all the most analytical correlations used in the literature to identify gas and water conning was performed to see the differences among them and with this dynamic integrated approach. On the other hand, for the production side this coupled model was applied to an offshore facility to see these reservoir effects in the transport system and how they impact in the pipeline and riser due to this abrupt entrance of gas and water changing the flow conditions, flow patterns, pressure drop and creating some instabilities in the separators caused by severe slugging.

The results of this analysis were very useful to understand the total production systems (reservoir-surface) behavior, predict the gas and water breakthrough, establish the critical rates to avoid these problems and see how the results differ in some cases with the common analytical correlations. Specific conditions in the pipeline and riser were established to quantify the slugging problems and evaluate different alternatives to eliminate the instabilities through proposing different scenarios such as gas injection in the riser, top side choking, etc. Application of this integrated approach has been very beneficial in recognizing the source of the problem, offer proper and feasible solutions in development and operational phases. In addition, validating and reducing uncertainty of related literature correlations and give to the production and reservoir engineers a quick and reliable way to know the critical rates that can support the decision-making process.
Optimization under Uncertainty for Reliable Unconventional Play Evaluation. A Case Study in Vaca Muerta Shale Gas Blocks, Argentina
Authors: Mehranfar Reza , Marquez Leonardo , Altman Raphael , kolivand Hassan , Orantes Rodrigo , Espinola Oswaldo
Published: June 2018

The objective of this work is to present a comprehensive workflow to optimize the value of a hydrocarbon asset evaluation project under high degrees of uncertainty. This workflow is applicable to both conventional and unconventional assets. However, because of the considerable level of subsurface uncertainty and high initial costs (mainly due to drilling and hydraulic fracturing operations), unconventional resources are good examples for demonstrating the benefits of the workflow. For the case of an unconventional asset, well spacing and perforation cluster spacing are usually the decision parameters that need to be optimized to increase its value.

The workflow begins with the construction of a representative base case single well gas simulation model for production history matching. Petrophysical, geological, geomechanical, stimulation, completions and production data are interpreted and analyzed together to better understand drivers that could be influencing the production. If this can be repeated with several wells in the block with sufficient production data, the process is enriched as so the level of confidence, as the range of history-matching parameters from these different wells across the block can be captured for sensitivity and uncertainty analysis. Several sets of sensitivities and uncertainty runs are then performed to get a probabilistic production profile in the presence of the most influential parameters. It is important to highlight that usually, the limited number of wells, short production histories, different dynamic behavior in neighboring blocks and the lack of necessary data to help understand well performance all contribute to the high uncertainty in predicting production.

Given the high cost of drilling and hydraulic fracturing and on the other hand the high gas price in Argentina, optimizing well spacing and cluster spacing are critical parameters in the process of unconventional resource evaluation considering the high degree of uncertainty.
Transient and Boundary Dominated Flow Temperature Analysis under Variable Rate Conditions
Authors: Mao Yilin , Zeidouni Mehdi
Published: June 2018

The assumption of constant rate production, which is often invalid for the extended period of production, is one of the fundamental premises for current analytical approaches of temperature transient analysis. This work addressed this issue by introducing novel analytical approaches to model temperature signals under variable rate conditions. The specific methods share underlying theories of superposition principle and production rate normalization from pressure transient analysis. With adapting these methods, cases with complex production history are modelled using analog cases producing with constant rate.

The analytical approach validation is performed by graphically and quantitative estimation of reservoir properties compared with synthetic temperature data. The estimation outputs of these methods include permeability, porosity, drainage area, and damaged zone properties, which are the application combinations from temperature transient analysis and reservoir limits testing. Monitoring well surveillance is extended to variable rate production in this paper. A case documented in the literature is addressed by this temperature analysis for which decent reservoir characterization results are obtained. The temperature analysis proposed in this paper extends the scope of temperature transient analysis to complex production constraints and demonstrates convincing results for practical purposes.
UTILIZAÇÃO DE FORMIGAS (HYMENOPTERA: FORMICIDAE) COMO BIOINDICADORAS EM PLANTIOS DE PINUS NO PARANÁ
Authors: Souza Karen Koch Fernandes de , Sousa Nilton José , Lima Pedro Pacheco dos Santos , Silva Ivan Crespo , Marques Eli Nunes
Published: June 2018

Os cultivos florestais transformam a paisagem e, como as demais monoculturas, apresentam baixa diversidade. A qualidade dos plantios pode ser investigada por meio da utilização bioindicadores. As formigas são amplamente empregadas como indicadores edáficos porque compreendem um grupo numericamente abundante, possuem ampla diversidade, ocupam diferentes nichos e, comparadas a outros seres vivos, são fáceis de amostrar, além de responderem as pressões ambientais. Esta pesquisa procurou realizar levantamento qualitativo e quantitativo das espécies de formigas de solo presentes em quatro ambientes (remanescente de Floresta Ombrófila Mista e três idades de plantios de Pinus sp.).  As coletas ocorreram em quatro etapas distribuídas ao longo de um ano. Em cada unidade amostral foi instalado um transecto de armadilha do tipo pitfall (adaptadas para uso com iscas de sardinha em óleo comestível) contendo cinco armadilhas com 10 m de distância. No total, foram coletados 3374 indivíduos pertencentes à Família Formicidae distribuídos em 23 espécies. A análise qualitativa mostrou que o gênero Pheidole teve o maior registro de indivíduos. O gênero Solenopsis foi o mais freqüente no plantio de Pinus taeda aos oito anos de idade, revelando que o gênero pode estar associado à ambientes perturbados enquanto que o gênero Pachycondyla sp. foi observado com maior freqüência  em ambiente com melhor estado de conservação.
FERTILIDADE DO SOLO E NUTRIÇÃO DA MANGUEIRA 'UBÁ' EM CONSÓRCIO COM BRAQUIÁRIA E SOB ADUBAÇÃO MINERAL, ORGÂNICA E ORGANOMINERAL
Authors: Pacheco Anália Lúcia Vieira , Borges Karina Schulz , De Freitas Gilberto Bernardo , Vieira Gerival
Published: June 2018

Devido ao clima apropriado ao cultivo da mangueira, a Zona da Mata mineira destaca-se pela produção de manga ‘Ubá’, contudo, a maior parte dos pomares é conduzida praticamente sem nenhum tipo de trato cultural, inclusive adubações e práticas de conservação do solo. Assim, o objetivo deste trabalho foi avaliar a fertilidade do solo e a nutrição da mangueira ‘Ubá’ após seis anos de cultivo com adubações mineral, orgânica e organomineral. Visando a proteção do solo e a ciclagem de nutrientes foi semeada Brachiaria brizantha nas entrelinhas do pomar, por ocasião do plantio das mangueiras. Utilizou-se cama de frango como adubo orgânico. O experimento iniciou em 2007, com quatro tratamentos: controle (apenas adubação de plantio), adubação mineral indicada para a cultura, adubação orgânica equivalente à adubação mineral e adubação organomineral (metade da dose da adubação mineral e metade da orgânica). Antes da implantação do pomar foi feita uma análise de solo da área experimental e ao término do experimento foram realizadas análises de solo e tecidos foliares. Adubações orgânicas proporcionaram maiores efeitos residuais de fósforo, potássio e magnésio no solo que adubações minerais e organominerais. O manejo da braquiária nas entrelinhas do pomar, através de roçadas periódicas, resultou em um aumento expressivo no teor de matéria orgânica do solo, além de propiciar a ciclagem de nutrientes. A adubação organomineral proporcionou uma nutrição mais equilibrada para as plantas.
DESEMPENHO DE MÁQUINAS E IMPLEMENTOS PARA MANEJO DE PALHAS E PLANTIO DIRETO NA AGRICULTURA ORGÂNICA
Authors: Favarato Luiz Fernando , Souza Jacimar Luis de , Pereira Victor Almeida , Guarçoni Rogério Carvalho
Published: June 2018

Um dos principais limitadores para a aplicação do sistema de plantio direto na agricultura orgânica é o manejo das plantas de cobertura, pela impossibilidade de uso de herbicidas para dessecação da palhada. Objetivou-se avaliar diversas formas de manejo de palhas e plantadoras, sobre diferentes plantas de cobertura, para sistema orgânico de produção, como alternativas operacionais e econômicas para o pequeno e grande produtor agrícola. Foram avaliados seis tipos de máquinas e implementos para roçagem e rolagem das plantas e três tipos de plantadoras. Verificou-se que os rolos-faca a trator e a microtrator foram as melhores opções, destacando-se com maiores eficiências operacionais e menores gastos de mão de obra, além de proporcionarem boas taxas de cobertura de solo. A plantadora de 2 linhas foi mais eficaz que as demais, além do potencial de ser utilizada no plantio direto em áreas maiores. Em pequenas áreas de agricultores familiares, o uso da matraca é uma boa opção, enquanto que a plantadora de 1 linha não apresenta rendimento de trabalho que justifique seu emprego no plantio direto na palha.
Earthquake Damage Predicting System of Songyuan Based on GIS
Authors: Zhenjiang Su , Meng Huang , Shaohui Xie , Dian Zhang , Zhe Wang
Published: June 2018

With the rapid development of cities, the research on urban seismic damage prediction should have a breakthrough based on the modern technology. The paper takes Songyuan of Jilin Province as the research object, and creates a spatial database by field data and Baidu maps. We simulate the earthquake by using the seismic intensity algorithm of the point source and the line source, use the spatial analysis method of PHP+GIS to simulate the influence at different earthquake levels on the urban buildings in Songyuan. At the same time, PHP, HTML and dynamic cutting technique were used to evaluate the disaster in 10 minutes after the earthquake. This system will provide technical support for the prevention of earthquake damage in Songyuan.
Examination of Factors Affecting Students’ Reading-Comprehension Achievement with Structural Equation Modeling
Authors: Ülper Hakan , Çetinkaya Gökhan , Dikici Ayhan
Published: June 2018

It is noted in the light of several studies
associated with the reading-comprehension skills that fluent word reading,
connectives knowledge and fluent text reading are closely related to the
comprehension skill. Hence it seems possible to create a model over these concepts
and their interrelationships. Within the scope of this research two different
models are proposed considering theoretical information. The
study group of the research was composed of 263 secondary school students at a
state school in Burdur province. Three different confirmatory factor analysis
(CFA) were performed to see whether factor structures were confirmed on the
sample by using the maximum estimate method of the AMOS 18 software. Analysis
of Covariance and Multivariate Analysis of Covariance were performed to
determine whether the demographic variables grade level and gender had a
significant effect on the scale scores. These analyzes were also performed in
the SPSS 18 program. It has been found that as the grade level of the students
increases, connective usage konowledge increases, the fluent silent word
reading, the fluent silent text reading, the reading comprehension and the
academic achievements increase as the grade level increases. This research
concluded that reading comprehension strongly and significantly predicted
academic achievement. But however, fluent silent text reading did not predict
reading comprehension significantly. According to the results of the research,
the model formed by the sub-dimensions of binding usage information shows
better fit.
Two-point boundary correlation functions of dense loop models
Authors: Morin-Duchesne Alexi , Jacobsen Jesper
Published: June 2018

We investigate six types of two-point boundary correlation functions
in the dense loop model. These are defined as ratios
Z/Z^0Z/Z0
of partition functions on the m\times nm×n
square lattice, with the boundary condition for
ZZ
depending on two points xx
and yy.
We consider: the insertion of an isolated defect (a) and a pair of
defects (b) in a Dirichlet boundary condition, the transition (c)
between Dirichlet and Neumann boundary conditions, and the connectivity
of clusters (d), loops (e) and boundary segments (f) in a Neumann
boundary condition.

For the model of critical dense polymers, corresponding to a
vanishing loop weight (\beta = 0β=0),
we find determinant and pfaffian expressions for these correlators. We
extract the conformal weights of the underlying conformal fields and
find \Delta = -\frac18Δ=−18,
00,
-\frac3{32}−332,
\frac3838,
11,
\tfrac \theta \pi (1+ \tfrac{2\theta}\pi)θπ(1+2θπ),
where \thetaθ
encodes the weight of one class of loops for the correlator of type f.
These results are obtained by analysing the asymptotics of the exact
expressions, and by using the Cardy-Peschel formula in the case where
xx
and yy
are set to the corners. For type b, we find a
\ln|x-y|ln|x−y|
dependence from the asymptotics, and a \ln (\ln n)ln(lnn)
term in the corner free energy. This is consistent with the
interpretation of the boundary condition of type b as the insertion of a
logarithmic field belonging to a rank two Jordan cell.

For the other values of \beta = 2 \cos \lambdaβ=2cosλ,
we use the hypothesis of conformal invariance to predict the conformal
weights and find \Delta = \Delta_{1,2}Δ=Δ1,2,
\Delta_{1,3}Δ1,3,
\Delta_{0,\frac12}Δ0,12,
\Delta_{1,0}Δ1,0,
\Delta_{1,-1}Δ1,−1
and \Delta_{\frac{2\theta}\lambda+1,\frac{2\theta}\lambda+1}Δ2θλ+1,2θλ+1,
extending the results of critical dense polymers. With the results for
type f, we reproduce a Coulomb gas prediction for the valence bond
entanglement entropy of Jacobsen and Saleur.
Job change and self-control of waste pickers: evidence from a field experiment in the Philippines
Authors: Yokoo Hide-Fumi , Ikuse Maki , Roda D. Romallosa Aries , Horita Masahide
Published: June 2018

Environmental policies may have a negative side effect on employment, often in a specific industry in the short run. Workers in regulated industries can be affected by losses in job-specific human capital. The informal sectors in developing countries are often associated with environmental pollution and thus targeted by such policies. Welfare loss due to this side effect can be problematic in developing countries, since they often lack safeguarding schemes, including unemployment insurance. Inducing workers in informal sectors to change their jobs can mitigate these negative side effects. This study examines efficient methods of inducing informal workers to change jobs. An alternative job is offered to informal workers at a dumpsite in the Philippines and whether changing the scheme of wage payment increases the acceptance of the offer is examined. The impacts of changing payment schemes are evaluated by using a randomized field experiment. The sampled 112 waste pickers each randomly receive one of four offers for an alternative job, and the number of those who accept the offer is observed to evaluate the impact of less frequent payment (i.e., once every three days instead of daily). Piece rates and fixed wages are also compared. Those offered less frequent payment are more likely to accept the job offer compared with those offered daily payment. This preferred payment scheme can mitigate the side effects of environmental policy and workers’ self-control problem related to savings, while minimizing moral hazard.
Prenatal Diagnosis and Fetal Outcomes of Cystic Hygroma: Experience of a Tertiary Hospital
Authors: Yakistiran Betul , Katlan Doruk Cevdi , Yuce Tuncay , Soylemez Feride
Published: June 2018

Objective: Cystic hygromas of nuchal origin are reported to be associated with fetal aneuploidy and structural anomalies in 50-80% of the cases. We aimed to report our experience on cystic hygromas via 18 cases.Study Design: We conducted a retrospective study based on a review of medical records of patients who had fetal septated cystic hygroma, diagnosed by ultrasonography, in the Ankara University School of Medicine, Department of Obstetrics and Gynecology, between 2012 and 2016. All patients were provided with genetic counselling and prenatal invasive diagnostic procedures were applied to obtain fetal karyotype.Results: We observed 18 cases of fetal cystic hygroma among these patients (0.39%). The abnormal karyotypes were: Turner syndrome (45X0) in 3 (16.7%), trisomy 21 in 2 (11.1%), trisomy 18 in 1 (5.6%) and mosaic Turner syndrome in 1 (5.6%) patient.Conclusion: The presence of cystic hygroma carries a high risk for aneuploidy and major structural malformations. Invasive prenatal diagnostic procedures for fetal karyotype analyses and parental counselling about poor perinatal prognosis is mandatory.
Spatiotemporal impacts of land use land cover changes on hydrology from the mechanism perspective using SWAT model with time-varying parameters
Authors: Li Yunyun , Chang Jianxia , Luo Lifeng , Wang Yimin , Guo Aijun , Ma Feng , Fan Jingjing
Published: June 2018

It is critically important to quantify the impact of land use land cover (LULC) changes on hydrology, and to understand the mechanism by which LULC changes affect the hydrological process in a river basin. To accurately simulate the hydrological process for a watershed like the Wei River Basin, where the surface characteristics are highly modified by human activities, we present an alternative approach of time-varying parameters in a hydrological model to reflect the changes in underlying land surfaces. The spatiotemporal impacts of LULC changes on watershed streamflow are quantified, and the mechanism that connects the changes in runoff generation and streamflow with LULC is explored. Results indicate the following: (1) time-varying parameters’ calibration is effective to ensure model validity when dealing with significant changes in underlying land surfaces; (2) LULC changes have significant impacts on the watershed streamflow, especially on the streamflow during the dry season; (3) the expansion of cropland is the major contributor to the reduction of surface water, causing decline in annual and dry seasonal streamflow. However, the shrinkage of woodland is the main driving force that decreases the soil water, thus contributing to a small increase in streamflow during the dry season.
Hydrodynamic disturbance on phosphorus release across the sediment–water interface in Xuanwu Lake, China
Authors: Bai Yu , Zeng Yuhong , Nie Bei , Jiang Helong , Zhang Xiaofeng
Published: June 2018

Excess phosphorus in lakes may cause algal blooming, and total phosphorus (TP) is an important index for lake eutrophication. As an important source of TP, lake sediment contributes a lot to TP release. TP release across the sediment–water interface varies with the hydrodynamic conditions of the overlying water, and in this paper the release characteristics of TP under hydrodynamic disturbance has been investigated. The sediment samples from Xuanwu Lake are collected and their release characteristics of TP under varying shear velocity are simulated in laboratory apparatus. Results show that increasing shear velocity contributes to the release of TP from sediment and the combination of varying shear velocity in different stages has a significant influence on the distribution of TP concentration. Further, the lattice Boltzmann method (LBM) is used to simulate the process of TP release from the sediment–water interface and the predicted values agree well with the measured data, which proves that the LBM can be used in simulating the process of TP release from sediment.
The Annual American Men's Internet Survey of Behaviors of Men Who Have Sex With Men in the United States: 2016 Key Indicators Report (Preprint)
Authors: Zlotorzynska Maria , Sullivan Patrick , Sanchez Travis
Published: June 2018

UNSTRUCTURED

The American Men’s Internet Survey (AMIS) is an annual Web-based behavioral survey of men who have sex with men (MSM) living in the United States. This Rapid Surveillance Report describes the fourth cycle of data collection (September 2016 through February 2017; AMIS 2016). The key indicators are the same as previously reported for AMIS (December 2013 through May 2014, AMIS 2013; November 2014 through April 2015, AMIS 2014; and September 2015 through April 2016, AMIS 2015). The AMIS survey methodology has not substantively changed since AMIS 2015. MSM were recruited from a variety of websites using banner advertisements and email blasts. Additionally, participants from AMIS 2015 who agreed to be recontacted for future research were emailed a link to the AMIS 2016 survey. Men were eligible to participate if they were ≥15 years old, resided in the United States, provided a valid US zone improvement plan code, and reported ever having sex with a man or identified as gay or bisexual. We examined demographic and recruitment characteristics using multivariable regression modeling (P<.05) stratified by participants’ self-reported HIV status. The AMIS 2016 round of data collection resulted in 10,166 completed surveys from MSM representing every US state, Puerto Rico, Guam, and the US Virgin Islands. Participants were mainly non-Hispanic white, over the age of 40 years, living in the Southern United States and urban areas, and recruited from general social networking websites. Self-reported HIV prevalence was 10.80% (1098/10,166). Compared to HIV-negative/unknown-status participants, HIV-positive participants were more likely to have had anal sex without a condom with a male partner in the past 12 months (75.77% vs 65.88%, P<.001) and more likely to have had anal sex without a condom with a serodiscordant or unknown-status partner (33.24% vs 16.06%, P<.001). The reported use of marijuana, methamphetamines, and other illicit substances in the past 12 months was higher among HIV-positive participants than among HIV-negative/unknown-status participants (28.05% vs 24.99%, 11.48% vs 2.16%, and 27.60% vs 18.22%, respectively; all P<.001). Most HIV-negative/unknown-status participants (79.93%, 7248/9068) reported ever having a previous HIV test, and 56.45% (5119/9068) reported undergoing HIV testing in the past 12 months. HIV-positive participants were more likely to report testing and diagnosis of sexually transmitted infections than HIV-negative/unknown-status participants (70.86% vs 40.13% and 24.04% vs 8.97%, respectively; both P<.001).
Relations Between the Use of Electronic Health and the Use of General Practitioner and Somatic Specialist Visits in Patients With Type 1 Diabetes: Cross-Sectional Study (Preprint)
Authors: Hansen Anne Helen , Broz Jan , Claudi Tor , Årsand Eirik
Published: June 2018

BACKGROUND

The prevalence of diabetes and the use of electronic health (eHealth) are increasing. People with diabetes need frequent monitoring and follow-up of health parameters, and eHealth services can be of great value. However, little is known about the association between the use of eHealth and provider-based health care services among people with diabetes.

OBJECTIVE

The objective of this study was to investigate the use of 4 different eHealth platforms (apps, search engines, video services, and social media sites) and associations with the use of provider-based health care visits among people diagnosed with type 1 diabetes mellitus (T1DM).

METHODS

We used email survey data collected from 1250 members of the Norwegian Diabetes Association (aged 18 to 89 years) in 2018. Eligible for analyses were the 523 respondents with T1DM. Using descriptive statistics, we estimated the use of eHealth and the use of general practitioners (GPs) and somatic specialist outpatient services. By logistic regressions, we studied the associations between the use of these provider-based health services and the use of eHealth, adjusted for gender, age, education, and self-rated health.

RESULTS

Of the sample of 523 people with T1DM, 90.7% (441/486) had visited a GP once or more, and 61.0% (289/474) had visited specialist services during the previous year. Internet search engines (such as Google) were used for health purposes sometimes or often by 84.0% (431/513), apps by 55.4% (285/514), social media (such as Facebook) by 45.2% (232/513), and video services (such as YouTube) by 23.3% (118/506). Participants aged from 18 to 39 years used all forms of eHealth more than people aged 40 years and older, with the exception of social media. The use of search engines was positively associated with the use of somatic specialist services (odds ratio 2.43, 95% CI 1.33-4.45). GP visits were not associated with any kind of eHealth use.

CONCLUSIONS

eHealth services are now widely used for health support and health information by people with T1DM, primarily in the form of search engines but often in the form of apps and social media as well. We found a positive association between the use of search engines and specialist visits and that people with T1DM are frequent users of eHealth, GPs, and specialist services. We found no evidence that eHealth reduces the use of provider-based health care; these services seem to be additional rather than alternative. Future research should focus on how health care services can meet and adapt to the high prevalence of eHealth use. Our results also indicate that many patients with T1DM do not visit specialist clinics once a year as recommended. This raises questions about collaboration in health care services and needs to be followed up in future research.