bluuebunny/crossref_metadata_2025 huggingface dataset:
Coronally advanced flap + connective tissue graft techniques for the treatment of deep gingival recession in the lower incisors. A controlled randomized clinical trial
Authors: Zucchelli Giovanni , Marzadori Matteo , Mounssif Ilham , Mazzotti Claudio , Stefanini Martina
Published: May 2014

Aim

The aim of this study was to compare the clinical and aesthetic outcomes of two different surgical approaches for the treatment of deep gingival recession affecting the mandibular incisors.

Methods

Fifty patients with Miller class I and II gingival recessions (≥ 3 mm) in the lower incisors were enrolled. Twenty‐five patients were randomly assigned to the control group and the other 25 patients to the test group. All defects were treated with the coronally advanced flap + connective tissue graft (CAF + CTG) and in the test group the labial submucosal tissue (LST) was removed. Post‐operative morbidity was evaluated at 1 week. Clinical and aesthetic evaluations were made at 1 year.

Results

Statistically greater recession reduction, probability of CRC (adjusted OR 7.94 95% CI = 1.88–33.50, p = 0.0024) and greater increase in GT were observed in the test group. Greater graft exposure and increase in KTH were demonstrated in the control group. Better aesthetics outcomes were observed in the test group. No statistically significant between groups differences were demonstrated in patient analgesic assumption and post‐operative discomfort and bleeding.

Conclusions

LST removal during CAF + CTG surgery is indicated to provide better root coverage and aesthetic outcomes in the treatment of gingival recessions affecting the lower incisors.
The serotonin transporter gene polymorphism 5‐HTTLPR moderates the effects of stress on attention‐deficit/hyperactivity disorder
Authors: van der Meer Dennis , Hartman Catharina A. , Richards Jennifer , Bralten Janita B. , Franke Barbara , Oosterlaan Jaap , Heslenfeld Dirk J. , Faraone Stephen V. , Buitelaar Jan K. , Hoekstra Pieter J.
Published: May 2014

Introduction

The role of the serotonin transporter gene polymorphism 5‐HTTLPR in attention‐deficit/hyperactivity disorder (ADHD) is unclear. Heterogeneity of findings may be explained by gene–environment interactions (GxE), as it has been suggested that S‐allele carriers are more reactive to psychosocial stress than L‐allele homozygotes. This study aimed to investigate whether 5‐HTTLPR genotype moderates the effects of stress on ADHD in a multisite prospective ADHD cohort study.

Methods

5‐HTTLPR genotype, as well as the number of stressful life events in the past 5 years and ongoing long‐term difficulties, was determined in 671 adolescents and young adults with ADHD, their siblings, and healthy controls (57.4% male, average age 17.3 years). Linear mixed models, accounting for family relatedness, were applied to investigate the effects of genotype, experienced stress, and their interaction on ADHD severity at time point T2, while controlling for ADHD severity at T1 (mean follow‐up time 5.9 years) and for comorbid internalizing problems at T2.

Results

The interaction between genotype and stress significantly predicted ADHD severity at T2 (p = .006), which was driven by the effect on hyperactivity–impulsivity (p = .004). Probing of the interaction effect made clear that S‐allele carriers had a significantly more positive correlation between stress and ADHD severity than L‐allele homozygotes.

Conclusion

The results show that the interaction between 5‐HTTLPR and stress is a mechanism involved particularly in the hyperactivity/impulsivity dimension of ADHD, and that this is independent of comorbid internalizing problems. Further research into the neurobiological mechanisms underlying this interaction effect is warranted.
A diffusion modeling approach to understanding contextual cueing effects in children with ADHD
Authors: Weigard Alexander , Huang‐Pollock Cynthia
Published: May 2014

Background

Strong theoretical models suggest implicit learning deficits may exist among children with Attention Deficit Hyperactivity Disorder (ADHD).

Method

We examine implicit contextual cueing (CC) effects among children with ADHD (n = 72) and non‐ADHD Controls (n = 36).

Results

Using Ratcliff's drift diffusion model, we found that among Controls, the CC effect is due to improvements in attentional guidance and to reductions in response threshold. Children with ADHD did not show a CC effect; although they were able to use implicitly acquired information to deploy attentional focus, they had more difficulty adjusting their response thresholds.

Conclusions

Improvements in attentional guidance and reductions in response threshold together underlie the CC effect. Results are consistent with neurocognitive models of ADHD that posit subcortical dysfunction but intact spatial attention, and encourage the use of alternative data analytic methods when dealing with reaction time data.
Limited genomic consequences of mixed mating in the recently derived sister species pair,Collinsia concolorandCollinsia parryi
Authors: Salcedo A. , Kalisz S. , Wright S. I.
Published: May 2014

Highly selfing species often show reduced effective population sizes and reduced selection efficacy. Whether mixed mating species, which produce both self and outcross progeny, show similar patterns of diversity and selection remains less clear. Examination of patterns of molecular evolution and levels of diversity in species with mixed mating systems can be particularly useful for investigating the relative importance of linked selection and demographic effects on diversity and the efficacy of selection, as the effects of linked selection should be minimal in mixed mating populations, although severe bottlenecks tied to founder events could still be frequent. To begin to address this gap, we assembled and analysed the transcriptomes of individuals from a recently diverged mixed mating sister species pair in the self‐compatible genus,Collinsia. The de novo assembly of 52 and 37 MbpC. concolorandC. parryitranscriptomes resulted in ~40 000 and ~55 000 contigs, respectively, both with an average contig size ~945. We observed a high ratio of shared polymorphisms to fixed differences in the species pair and minimal differences between species in the ratio of synonymous to replacement substitutions or codon usage bias implying comparable effective population sizes throughout species divergence. Our results suggest that differences in effective population size and selection efficacy in mixed mating taxa shortly after their divergence may be minimal and are likely influenced by fluctuating mating systems and population sizes.
Dioecy is associated with higher diversification rates in flowering plants
Authors: Käfer J. , de Boer H. J. , Mousset S. , Kool A. , Dufay M. , Marais G. A. B.
Published: May 2014

In angiosperms, dioecious clades tend to have fewer species than their nondioecious sister clades. This departure from the expected equal species richness in the standard sister clade test has been interpreted as implying that dioecious clades diversify less and has initiated a series of studies suggesting that dioecy might be an 'evolutionary dead end‘. However, two of us recently showed that the ‘equal species richness‘ null hypothesis is not valid in the case of derived char acters, such as dioecy, and proposed a new test for sister clade comparisons; preliminary results, using a data set available in the litterature, indicated that dioecious clades migth diversify more than expected. However, it is crucial for this new test to distinguish between ancestral and derived cases of dioecy, a criterion that was not taken into account in the available data set. Here, we present a new data set that was obtained by searching the phylogenetic literature on more than 600 completely dioecious angiosperm genera and identifying 115 sister clade pairs for which dioecy is likely to be derived (including > 50% of the dioecious species). Applying the new sister clade test to this new dataset, we confirm the preliminary result that dioecy is associated with an increased diversification rate, a result that does not support the idea that dioecy is an evolutionary dead end in angiosperms. The traits usually associated with dioecy, that is, an arborescent growth form, abiotic pollination, fleshy fruits or a tropical distribution, do not influence the diversification rate. Rather than a low diversification rate, the observed species richness patterns of dioecious clades seem to be better explained by a low transition rate to dioecy and frequent losses.
Late‐life and intergenerational effects of larval exposure to microbial competitors in the burying beetle Nicrophorus vespilloides
Authors: McLean A. H. C. , Arce A. N. , Smiseth P. T. , Rozen D. E.
Published: May 2014

Intergenerational effects can have either adaptive or nonadaptive impacts on offspring performance. Such effects are likely to be of ecological and evolutionary importance in animals with extended parental care, such as birds, mammals and some insects. Here, we studied the effects of exposure to microbial competition during early development on subsequent reproductive success in the burying beetle Nicrophorus vespilloides, an insect with elaborate parental care. We found that exposure to high levels of microbial competition both during a female's larval development and during her subsequent reproduction resulted in females rearing smaller broods than those exposed to lower levels of microbial competition. To determine whether these differences arose before or after offspring hatching, a cross‐fostering experiment was conducted. Our results demonstrate that the impact of larval competition with microbes for resources extends into adult life and can negatively affect subsequent generations via impacts on the quality of parental care provided after hatching. However, we also find evidence for some positive effects of previous microbial exposure on prehatch investment, suggesting that the long‐term results of competition with microbes may include altering the balance of parental investment between prehatch and post‐hatch care.
The founding of Mauritian endemic coffee trees by a synchronous long‐distance dispersal event
Authors: Nowak M. D. , Haller B. C. , Yoder A. D.
Published: May 2014

The stochastic process of long‐distance dispersal is the exclusive means by which plants colonize oceanic islands. Baker's rule posits that self‐incompatible plant lineages are unlikely to successfully colonize oceanic islands because they must achieve a coordinated long‐distance dispersal of sufficiently numerous individuals to establish an outcrossing founder population. Here, we show for the first time that Mauritian Coffea species are self‐incompatible and thus represent an exception to Baker's rule. The genus Coffea (Rubiaceae) is composed of approximately 124 species with a paleotropical distribution. Phylogenetic evidence strongly supports a single colonization of the oceanic island of Mauritius from either Madagascar or Africa. We employ Bayesian divergence time analyses to show that the colonization of Mauritius was not a recent event. We genotype S‐RNase alleles from Mauritian endemic Coffea, and using S‐allele gene genealogies, we show that the Mauritian allelic diversity is confined to just seven deeply divergent Coffea S‐RNase allelic lineages. Based on these data, we developed an individual‐based model and performed a simulation study to estimate the most likely number of founding individuals involved in the colonization of Mauritius. Our simulations show that to explain the observed S‐RNase allelic diversity, the founding population was likely composed of fewer than 31 seeds that were likely synchronously dispersed from an ancestral mainland species.
Life history, predation and flight initiation distance in a migratory bird
Authors: Møller A. P.
Published: May 2014

Life‐history trade‐offs occur as a consequence of the compromise between maximization of different components such as the size and the number of clutches. Flight initiation distance (FID) potentially constitutes a general proximate factor influencing such trade‐offs reflecting the risks that individuals take. Therefore, greater investment in reproduction occurs at a higher risk of death, resulting in selection for efficient flight morphology. I analysed long‐term data onFIDin a population of barn swallowsHirundo rusticaduring 1984–2013 with 2196 records ofFIDfor 1789 individuals.FIDhad a repeatability of 0.62 (SE = 0.04) and a heritability of 0.48 (SE = 0.07).FIDvaried between individuals and sites, and it increased over time as climate ameliorated.FIDshowed a U‐shaped relationship with age, with young and very old individuals having the longestFIDs. Barn swallows that arrived early from spring migration, started to breed early and produced many fledglings had the longestFID. Individuals with the longest tails had the longestFID, and individuals with the shortest aspect ratios and wing loadings had the longestFID. Individuals that died from predation had shorterFIDthan survivors. These findings are consistent with the hypothesis thatFIDrelates directly to life history, with longerFIDs being associated with smaller levels of risk‐taking.
Proton Pump Inhibitors and Functional Decline in Older Adults Discharged From Acute Care Hospitals
Authors: Corsonello Andrea , Maggio Marcello , Fusco Sergio , Adamo Bakhita , Amantea Diana , Pedone Claudio , Garasto Sabrina , Ceda Gian Paolo , Corica Francesco , Lattanzio Fabrizia , Antonelli Incalzi Raffaele
Published: May 2014

Objectives

To investigate the relationship between use of proton pump inhibitors (PPIs) and incident dependency in older adults discharged from acute care hospitals.

Design

Prospective observational study.

Setting

Eleven geriatric and internal medicine acute care wards located throughout Italy.

Participants

Individuals (mean age 79.2 ± 5.5) who were not completely dependent at the time of discharge from participating wards (N = 401).

Measurements

The outcome of interest was the loss of at least one basic activity of daily living (ADL) from discharge to the end of follow‐up (12 months). The relationship between PPI use and functional decline was investigated using logistic regression analysis before and after propensity score matching.

Results

Use of PPIs was significantly associated with functional decline before (odds ratio (OR) = 1.75, 95% confidence interval (CI) = 1.17–2.60) and after propensity score matching (OR = 2.44; 95% CI = 1.36–4.41). Other predictors of functional decline were hypoalbuminemia (OR = 3.10, 95% CI = 1.36–7.10 before matching, OR = 2.81, 95% CI = 1.09–7.77 after matching) and cognitive impairment (OR = 4.08, 95% CI = 1.63–10.2 before matching, OR = 6.35, 95% CI = 1.70–24.0 after matching).

Conclusion

Use of PPIs is associated with functional decline during 12 months of follow‐up in older adults discharged from acute care hospitals.
Quality of End‐of‐Life Care Among Rural Medicare Beneficiaries With Colorectal Cancer
Authors: Watanabe‐Galloway Shinobu , Zhang Wanqing , Watkins Kate , Islam KM , Nayar Preethy , Boilesen Eugene , Lander Lina , Wang Hongmei , Qiu Fang
Published: May 2014

Background

Although previous research has documented rural disparities in hospice use, limited data exist on the roles of geographic access in different types of end‐of‐life indicators among cancer survivors.

Methods

Medicare claims data were used to identify beneficiaries with colorectal cancer who died in 2008 (N = 34,975). We evaluated rural‐urban differences in ER visits 90 days before death, inpatient hospital admissions ≤90 days before death, intensive care unit (ICU) use ≤90 days before death, hospice care use at any time, and hospice enrollment <3 days before death.

Results

About 60% of beneficiaries in rural areas lived in counties with the 2 lowest socioecomonic levels compared to only 5.3% of beneficiaries in metropolitan areas. After adjusting for demographic factors and comorbidities, beneficiaries in rural counties had a lower number of ICU days (RR = 0.65) and were less likely to ever use hospice (OR = 0.78) compared to those in metropolitan counties. Beneficiaries from racial/ethnic minority groups, those with lower socioeconomic status, and those with a higher comorbidity index were less likely to ever use hospice but they tended to use ER, inpatient care, and ICU.

Conclusions

Evidence for disparities due to geographic access and socioeconomic factors warrant increased efforts to remove systemic and structural barriers. Future research should focus on exploring and evaluating potential policy and practice interventions to improve the quality of life among elderly cancer survivors living in rural communities and those from socioeconomically disadvantaged backgrounds.
Characteristic haemodynamic changes of cirrhosis may influence the diagnosis of portopulmonary hypertension
Authors: Chiva Teresa , Ripoll Cristina , Sarnago Fernando , Rincón Diego , Gómez‐Camarero Judith , Galindo Evelyn , Catalina María‐Vega , Elizaga Jaime , Bañares Rafael
Published: May 2014

Background & Aims

Diagnosis of portopulmonary hypertension (POPH) is based on the presence of portal hypertension and the same haemodynamic criteria as pulmonary arterial hypertension (PAH). However, the typical hyperdynamic circulation of cirrhosis may have some impact on the diagnosis of POPH. The aim was to compare the haemodynamic pattern of the pulmonary circulation between cirrhotics and non‐cirrhotics, including patients with PAH.

Patients and Methods

600 patients with cirrhosis [male 77.5%, age 54 (47–60) years, Child A: 14.7%, B: 54.3%, C: 31%] received right heart catheterization. For comparison, 118 non‐cirrhotic patients [male 60%, age 64 (53–65) years] with right heart catheterization and PCWP <20 mmHg were included. Both were divided into 3 groups, A: absence of pulmonary arterial hypertension; B or intermediate group: MPAP >25 mmHg, PVR 120–240 dyn s cm−5 and PCWP <15 mmHg (or PCWP >15 mmHg with TPG ≥12 mmHg); C: pulmonary arterial hypertension (same criteria as B except PVR ≥240 dyn s cm−5).

Results

Distribution of patients with cirrhosis was A 583, B 7 and C 10. Prevalence of POPH was 1.7%. Cirrhotics had lower SVR and greater CO than non‐cirrhotics (P < 0.05). Interestingly, patients with cirrhosis without PAH (groups A and B) had lower PVR (P < 0.05) when comparing with non‐cirrhotics, while no differences in PVR were observed in group C. However, mean TPG was greater in group C of cirrhotics [36.6 mmHg (12.2) vs. 27.1 mmHg (10.1); P = 0.034].

Conclusions

Patients with cirrhosis have lower PVR. TPG is greater in POPH than PAH. Characteristic haemodynamic changes of cirrhosis may influence the diagnosis of POPH.
Use and reimbursement of off‐label drugs in pediatric anesthesia: the Italian experience
Authors: Salvo Ida , Landoni Giovanni , Mucchetti Marta , Cabrini Luca , Pani Luca
Published: May 2014

Background

Most of the drugs used in anesthesia are off‐label in children even if they present solid clinical evidence in adults. This lack of authorization is caused by multiple factors including the difficulty in conducting research in this area (due to the ethical concerns and/or the low number of available participants, the high variability of the outcome measures) and the lack of economic interest of the pharmaceutical companies (due to the limited market).

Objective

Define a list of medicinal products commonly used off‐label in pediatrics anesthesia to be reimbursed by Italian National Health System.

Methods and results

We hereby describe the methodological framework used to allow reimbursed use of a list of medicinal products, widely used off‐label in pediatric patients, ensuring the best therapeutic results with the lowest possible risk for children. A task force of pediatric anesthesiologists from Italy petitioned the Italian Medicines Agency (AIFA) to allow a number of commonly utilized but off‐label drugs for pediatric anesthesia to be reimbursed for specific indications. For each drug, both the supporting literature and expert opinion were used, and the resulting list of drugs allowed to be used/reimbursed officially by AIFA was significantly expanded. This paper documents one approach to the problem of off‐label use of drugs for pediatric patients that can be a model for future efforts.

Conclusion

Continuous efforts are needed from government institutions and sponsors on drug development and on drug approval process in pediatrics, as research on drug effectiveness and safety is mandatory in children as in adults. At the same time, clinicians must become more familiar with the drug‐approval process, participate to sponsored trials, and perform ztrials themselves.
Garment Industry in Sri Lanka and the Removal of GSP Plus by EU
Authors: Bandara Jayatilleke S. , Naranpanawa Athula
Published: May 2014

The ready‐made garment industry plays an important role in Sri Lanka both in terms of export earnings and poverty alleviation through employment generation. Following the removal of GSP Plus by EU in 2010 on the basis of alleged human right violations by the Sri Lankan government during the last stage of the civil war in 2009 and after, it currently faces serious challenges in exporting to the EU, its major market. Given the important role of the ready‐made garment industry in poverty alleviation through employment generation, the impact of removal of GSP plus on the poor is examined in this paper. The empirical results of this study demonstrate that poverty and income inequality are expected to be exacerbated in Sri Lanka as a result of the removal of GSP Plus by the EU using non‐economic reasons such as human rights violation. The results are also relevant for the renewed emphasis on trade preferences as a potential instrument for the Millennium Development Goals and the debate on how trade preferences are to be designed to maximise their effectiveness in stimulating a manufacturing supply response.
Aspects of Experimental Errors and Data Reduction Schemes From Spherical Indentation of Isotropic Materials
Authors: Phadikar J. K. , Bogetti T. A. , Karlsson A. M.
Published: May 2014

Sensitivity to experimental errors determines the reliability and usefulness of any experimental investigation. Thus, it is important to understand how various test techniques are affected by expected experimental errors. Here, a semi-analytical method based on the concept of condition number is explored for systematic investigation of the sensitivity of spherical indentation to experimental errors. The method is employed to investigate the reliability of various possible spherical indentation protocols, providing a ranking of the selected data reduction protocols from least to most sensitive to experimental errors. Explicit Monte Carlo sensitivity analysis is employed to provide further insight of selected protocol, supporting the ranking. The results suggest that the proposed method for estimating the sensitivity to experimental errors is a useful tool. Moreover, in the case of spherical indentation, the experimental errors must be very small to give reliable material properties.
Pulsed Thermal Imaging Measurement of Thermal Properties for Thermal Barrier Coatings Based on a Multilayer Heat Transfer Model
Authors: Sun J. G.
Published: May 2014

Thermal properties of thermal barrier coatings (TBCs) are important parameters for the safe and efficient operation of advanced turbine engines. This paper presents a new method, the pulsed thermal imaging–multilayer analysis (PTI–MLA) method, which can measure the coating thermal conductivity and heat capacity distributions over an entire engine component surface. This method utilizes a multilayer heat transfer model to analyze the surface temperature response acquired from a one-sided pulsed thermal imaging experiment. It was identified that several experimental system parameters and TBC material parameters may affect the coating surface temperature response. All of these parameters were evaluated and incorporated as necessary into the formulations. The PTI–MLA method was demonstrated by analyzing three TBC samples, and the experimental results were compared with those obtained from other methods.
Rationalized Concise Descriptions of Fluid Motions in an Oscillating/Pulsating Heat Pipe
Authors: Furukawa Masao
Published: May 2014

Various ways developed so far in modeling oscillating/pulsating heat pipes (OHPs/PHPs) are briefly reviewed to find which way would be serviceable for design purposes and also be helpful to mathematically plainly describe oscillatory/circulatory motions of the charged working fluid. A selected way basically follows Ma's approach but a theoretically new attempt is made to derive the oscillation angular frequency ratio from two differently represented expressions of the oscillation velocity. A two-phase flow and evaporative/condensing heat transfer analysis is then carried out to get the wave equation of pressure oscillation. Finally obtained are closed-form algebraic expressions, providing us with convenient means of predicting the oscillation frequency- and-amplitude and the wave velocity. To demonstrate the applicability of those expressions, numerical comparisons are extensively done between our predictions and many other ones.
Simulating Bluff-Body Flameholders: On the Use of Proper Orthogonal Decomposition for Wake Dynamics Validation
Authors: Blanchard Ryan , Ng Wing , Lowe Todd K. , Vandsburger Uri
Published: May 2014

In this article, we describe a novel use of proper orthogonal decomposition (POD) for validation of the structure of dominant flow features in the wake of a bluff-body flameholder. Large-eddy simulations (LES) using both FLUENT and OpenFOAM were conducted based on experiments with planar particle-image velocimetry (PIV) measurements of the same geometry and conditions. With the vision of extending the LES to reacting flows, a validation process is presented that involves a comparison of experimental and computational results, beginning with single-point mean statistics and then extended to the dynamic modes of the data sets as obtained using POD of the instantaneous flow field results. The results exhibit quantitative agreement between both shapes and mode magnitudes for the first POD modes of the measured and simulated data.
Experimental and Modeling Study of the Effect of Manufacturing Deviations on the Flow Characteristics of Tangential Intake Port in a Diesel Engine
Authors: Lu Zhen , Wang Tianyou , Liu Shuliang , Lin Zhiqiang , Han Yiyong
Published: May 2014

The intake port flow characteristics in an internal combustion engine significantly affect its power output, fuel economy, and emissions. To optimize the flow characteristics in the intake port, increasing attention has been paid to its design process. However, the casting and machining processes of the intake port are underappreciated, which may introduce significant deviations, leading to undesirable variation of intake port flow and subsequent deterioration in engine combustion and emissions. In this paper, steady flow tests were carried out on a four-valve diesel engine to investigate how and to what extent the casting and machining deviations of the intake port influence the in-cylinder flow characteristics. The results show that these deviations lead to the variation of swirl ratio up to 20%. Then, computational fluid dynamics (CFD) simulation was conducted for understanding the reason. It is indicated that higher tolerance is needed during the casting and machining processes. For example, in order to control the variation of swirl ratio within 10%, the inclined angle should be controlled at less than 1 deg, the eccentric distance should be restricted to less than 0.5 mm, and the swelling thickness should be limited to less than 1 mm.
Simulating Bluff-Body Flameholders: On the Use of Proper Orthogonal Decomposition for Combustion Dynamics Validation
Authors: Blanchard Ryan , Wickersham A. J. , Ma Lin , Ng Wing , Vandsburger Uri
Published: May 2014

Contemporary tools for experimentation and computational modeling of unsteady and reacting flow open new opportunities for engineering insight into dynamic phenomena. In this article, we describe a novel use of proper orthogonal decomposition (POD) for validation of the unsteady heat release of a turbulent premixed flame stabilized by a vee-gutter bluff-body. Large-eddy simulations were conducted for the same geometry and flow conditions as examined in an experimental rig with chemiluminescence measurements obtained with a high-speed camera. In addition to comparing the experiment to the simulation using traditional time-averaging and pointwise statistical techniques, the dynamic modes of each are isolated using proper orthogonal decomposition (POD) and then compared mode-by-mode against each other. The results show good overall agreement between the shapes and magnitudes of the first modes of the measured and simulated data. A numerical study of into the effects of various simulation parameters on these heat release modes showed significant effects on the flame's effective angle but also on the size, shape, and symmetry patterns of the flame's dynamic modes.
Transient Response Control of Two-Mass System via Polynomial Approach
Authors: Qiao Yue , Cao Junyi , Ma Chengbin
Published: May 2014

This paper discusses the application of polynomial method in the transient response control of a benchmark two-mass system. It is shown that transient responses can be directly addressed by specifying the so-called characteristic ratios and the generalized time constant. The nominal characteristic ratio assignment (CRA) is a good starting point for controller design. And the characteristic ratios with lower indices have a more dominant influence. Two practical low-order control configurations, the integral-proportional (IP) and modified-integral-proportional-derivative (m-IPD) controllers are designed. The primary design strategy of the controllers is to guarantee the lower-index characteristic ratios to be equal to their nominal values, while the higher-index characteristic ratios are determined by the interaction with the generalized time constant and the limits imposed by zeros, a specific control configuration, etc. The demonstrated relationship between the transient responses and the assignments of characteristic ratios and generalized time constant in simulation and experiments explains the effectiveness of the polynomial-method-based controller design.
ECMS Controller Robustness in Flex-Fuel Hybrid Vehicles
Authors: Manzie Chris , Grondin Olivier , Sciarretta Antonio , Zito Gianluca
Published: May 2014

Control algorithms for hybrid vehicles have undergone extensive research and development leading to near-optimal techniques being employed and demonstrated in prototype vehicles over the previous decade. The use of different implementations of optimal controllers is inevitably linked through the assumed knowledge of the system being controlled. With the growing interest in alternative fuels, such as ethanol, liquified petroleum gas (LPG), and compressed natural gas (CNG) due to enhanced emissions and fuel security considerations, a natural extension is to hybridize these engines to improve fuel economy and CO2 emissions. This step is complicated by the potential variation in fuel composition seen with many gasoline and diesel alternatives, leading to uncertainty in the models used by the hybrid powertrain controller. This work investigates the robustness of one hybrid powertrain optimal control approach, the equivalent consumption minimization strategy (ECMS). Two case studies are performed involving experimentally obtained engine maps from two significantly different prototypes flex-fuel vehicles to quantify the potential impact of map error caused by incorrect fuel assumptions.
Borehole Stability Analysis in Deepwater Shallow Sediments
Authors: Chuanliang Yan , Jingen Deng , Xiangdong Lai , Xiaorong Li , Yongcun Feng
Published: May 2014

Deepwater shallow sediment is less-consolidated, with a rock mechanical behavior similar to saturated soil. It is prone to borehole shrinkage and downhole leakage. Assume the deepwater shallow sediments are homogeneous, isotropic, and ideally elastoplastic materials, and formation around the borehole is divided into elastic and plastic zone. The theories of small deformation and large deformation are, respectively, adopted in the elastic and plastic zone. In the plastic zone, Mohr–Coulomb strength criterion is selected. The stress and deformation distributions in these two zones, and the radius of plastic zone are derived. The collapse pressure calculation formula of deepwater shallow sediments under the control of different shrinkage rates is obtained. With the introduction of excess pore pressure theory in soil mechanics, the distribution rule of excess pore pressure in these two zones is obtained. Combined with hydraulic fracturing theory, the fracture mechanism of shallow sediments is analyzed and the theoretical formula of fracture pressure is given. The calculation results are quite close to the practically measured results. So the reliability of the theory is confirmed.
Effect of Drillstring Deflection and Rotary Speed on Annular Frictional Pressure Losses
Authors: Erge Oney , Ozbayoglu Mehmet E. , Miska Stefan Z. , Yu Mengjiao , Takach Nicholas , Saasen Arild , May Roland
Published: May 2014

Keeping the drilling fluid equivalent circulating density in the operating window between the pore and fracture pressure is a challenge, particularly when the gap between these two is narrow, such as in offshore, extended reach, and slim hole drilling applications usually encountered in shale gas and/or oil drilling. To overcome this challenge, accurate estimation of frictional pressure loss in the annulus is essential. A better estimation of frictional pressure losses will enable improved well control, optimized bit hydraulics, a better drilling fluid program, and pump selection. Field and experimental measurements show that pressure loss in annuli is strongly affected by the pipe rotation and eccentricity. The major focus of this project is on a horizontal well setup with drillstring under compression, considering the influence of rotation on frictional pressure losses of yield power law fluids. The test matrix includes flow through the annulus for various buckling modes with and without the rotation of the inner pipe. Sinusoidal, helical, and transition from sinusoidal to helical configurations with and without the drillstring rotation were investigated. Helical configurations with two different pitch lengths are compared. Eight yield power law fluids are tested and consistent results are observed. The drillstring rotation patterns and buckling can be observed due to experimental facility's relatively longer and transparent test section. At the initial position, inner pipe is lying at the bottom due to its extensive length, suggesting a fully eccentric annular geometry. When the drillstring is rotated, whirling, snaking, irregular motions are observed. This state is considered as a free drillstring configuration since there is no prefixed eccentricity imposed on the drillstring. The reason for such design is to simulate the actual drilling operations, especially the highly inclined and horizontal drilling operations. Results show that rotating the drillstring can either increase or decrease the frictional pressure losses. The most pronounced effect of rotation is observed in the transition region from laminar to turbulent flow. The experiments with the buckled drillstring showed significantly reduced frictional pressure losses compared to the free drillstring configuration. Decreasing the length of the pitch caused a further reduction in pressure losses. Using the experimental database, turbulent friction factors for buckled and rotating drillstrings are presented. The drilling industry has recently been involved in incidents that show the need for critical improvements for evaluating and avoiding risks in oil/gas drilling. The information obtained from this study can be used to improve the control of bottomhole pressures during extended reach, horizontal, managed pressure, offshore, and slim hole drilling applications. This will lead to improved safety and enhanced optimization of drilling operations.
Shale Caprock/Acidic Brine Interaction in Underground CO2 Storage
Authors: Olabode Abiola , Radonjic Mileva
Published: May 2014

Shale caprock integrity is critical in ensuring that subsurface injection and storage of anthropogenic carbon dioxide (CO2) is permanent. The interaction of clay-rich rock with aqueous CO2 under dynamic conditions requires characterization at the nanoscale level due to the low-reactivity of clay minerals. Geochemical mineral–fluid interaction can impact properties of shale rocks primarily through changes in pore geometry/connectivity. The experimental work reported in this paper applied specific analytical techniques in investigating changes in surface/near-surface properties of crushed shale rocks after exposure (by flooding) to CO2–brine for a time frame ranging between 30 days and 92 days at elevated pressure and fractional flow rate. The intrinsically low permeability in shale may be altered by changes in surface properties as the effective permeability of any porous medium is largely a function of its global pore geometry. Diffusive transport of CO2 as well as carbon accounting could be significantly affected over the long term. The estimation of permeability ratio indicated that petrophysical properties of shale caprock can be doubled.
Particle Image Velocimetry Measurement and Computational Fluid Dynamic Simulations of the Unsteady Flow Within a Rotating Disk Cavity
Authors: Luo Xiang , Liu Dongdong , Wu Hongwei , Tao Zhi
Published: May 2014

In this article a combined experimental and numerical investigation of the unsteady mixing flow of the ingestion gas and rim sealing air inside a rotating disk cavity was carried out. A new test rig was set up, and the experiments were conducted on a 1.5-stage turbine rotor disk and included pressure measurements. The flow structure of the mixing region of the ingestion gas and sealing air in cavity was measured using the particle image velocimetry (PIV) technique. To complement the experimental investigation and to aid in understanding the flow mechanism within the cavity, a three-dimensional (3D) unsteady computational fluid dynamic (CFD) analysis was undertaken. Both simulated and experimental results indicated that near the rotating disk, (i) a large amount of the ingestion gas will turn around and flow out the cavity due to the impact of the centrifugal force and the Coriolis force, (ii) a small amount of ingestion gas will mix transiently with the sealing air inside the cavity, whereas near the static disk, (iii) the ingestion gas will flow into the cavity along the static wall and mix with the sealing air.
Aerodynamic Analysis of Steam Turbine Feed-Heating Steam Extractions
Authors: Rosic Budimir , Maria Mazzoni Cosimo , Bignell Zoe
Published: May 2014

Feed-heating in steam turbines, the use of steam extracted from the turbine to heat the feed-water, is known to raise the plant efficiency and so is included in most steam turbine power plant designs. The steam is extracted through an extraction slot that runs around the casing downstream of a rotor blade row. The slot is connected to a plenum, which runs around the outside of the turbine annulus. Steam flows to the feed-heaters through a pipe connected usually to the bottom of the plenum. The steam extraction is driven by a circumferentially nonuniform pressure gradient in the plenum. This causes the mass flow rate of steam extracted to vary circumferentially, which affects the main passage flow downstream of the extraction point. The flow in the extraction plenum and the influence of the steam extraction on the mainstream aerodynamics is analyzed numerically in this paper. A complete annulus with the extraction slot and plenum together with the downstream stator and rotor blade rows is modeled in this study. The results reveal a highly nonuniform steam extraction around the annulus with the highest extraction rates from the bottom nearest the extraction pipe and the lowest at the top of the annulus. This difference in extraction rates modifies the flow angle and loss circumferential distribution downstream of the stator blade row. This study finds out that the distribution of steam extraction around the annulus and its influence on the main passage flow could be greatly improved by changing the shape and increasing the volume of the extraction slot and plenum.
Gelation Performance and Microstructure Study of Chromium Gel and Phenolic Resin Gel in Bulk and Porous Media
Authors: Zhang Jian , He Hong , Wang Yefei , Xu Xiaoli , Zhu Yuejun , Li Ruyin
Published: May 2014

Polymer gel has been widely used to control excessive water production in many mature oilfields; however, there still exist some problems concerning the differences between gelation behavior in bulk and porous media. In this paper, the gelation time and microstructures of chromium gel and phenolic resin gel in bulk and porous media were studied. Results showed that for chromium gel, the initial gelation time in porous media was about 2.5–3.5 times of that in bulk and final gelation time in porous media was about 6.0–7.0 times of that in bulk. While for phenolic resin gel, the initial gelation time in porous media was about 1.0–1.5 times of that in bulk, and final gelation time in porous media was about 1.5–2.0 times of that in bulk. The morphology of chromium gel and phenolic resin gel in bulk were dendritic shape structure and 3D network structure, respectively. However, the morphology of chromium gel and phenolic resin gel in porous media were both dense gel membranes at low magnification. While at higher magnification, compared with the branchlike cluster structure of chromium gel in porous media, the network of phenolic resin gel was more developed. The experimental results can provide the basis for determining well shut off time and reveal the differences of gel microstructures between the chromium gel and phenolic gel in bulk and porous media.
Semi-Analytical Proxy for Vapex Process Modeling in Heterogeneous Reservoirs
Authors: Shi Jindong , Leung Juliana Y.
Published: May 2014

Vapex (vapor extraction) is a nonthermal process that has significant potential in providing a more environmentally friendly and energy-efficient alternative to steam injection. Vaporized solvent injected in-situ dissolves into the oil and reduces oil viscosity, allowing the oil to flow to a horizontal production well via gravitational forces. While compositional simulators are available for assessing the Vapex performance, the simulation process may become difficult when taking into account the uncertainty due to reservoir heterogeneity. A semi-analytical proxy is proposed to model the process, in a way analogous to the steam-assisted gravity drainage (SAGD) model described by Butler, who demonstrated the similarity between two processes with a series of Hele-Shaw experiments and derived an analytical steady-state flow rate relationship that is comparable with the SAGD case. Solvent concentration and intrinsic diffusivity are introduced in this model instead of temperature and thermal diffusivity in SAGD. In this paper, analytical solutions and implementation details for the Vapex proxy are presented. The proposed approach is then applied to various reservoirs discretized with spatially varying rock porosity and permeability values; bitumen drainage rate and solvent penetration are calculated sequentially at grid blocks along the solvent–bitumen interface over incremental time steps. Results from this model are compared against experimental data available in the literature as well as detailed compositional simulation studies. Computational requirement of the proxy in comparison with numerical simulations is also emphasized. An important contribution from this work is that process physics are built directly into this proxy, giving it an advantage over other data-driven modeling approaches (e.g., regression). It can be used as an efficient alternative to expensive detailed flow simulations. It presents an important potential for assessing the uncertainty due to multiscale heterogeneity on effective mass transfer and the resulting recovery performance, as well as assisting decisions-making for future pilot and field development.
Cobalt Sulphate as an Alternative Counter Electrode Material in Dye Sensitized Solar Cells
Authors: Shelke R. S. , Thombre S. B. , Patrikar S. R.
Published: May 2014

Dye sensitized solar cells (DSSCs) have become an attractive and cheap device for the conversion of solar light into electrical energy. The glass substrate coated with platinum is widely used as a counter electrode because of its high catalytic activity for iodide/triiodide redox reaction. This paper presents a systematic comparative study on exploring and understanding the performance of DSSC using cobalt sulphate as a counter electrode material in place of platinum or graphite. However, platinum being costly, other materials like graphite or carbon black etc. also used in DSSCs but with reduced conversion efficiency. Later in the present study, it was found that, the DSSCs made with graphite as a counter electrode does not have long term stability. It may be mentioned here that cobalt sulphate so far has never been used as a counter electrode in DSSC fabrication. It is found that DSSCs made with the cobalt sulphate as a counter electrode gives better photovoltaic performance over that with the graphite-coated counter electrode and can be a suitable alternative for DSSCs in future. The paper also presents a comparative study on the performance degradation of DSSCs using cobalt sulphate and graphite as a counter electrodes. The investigation was carried out initially for 60 days in succession and then after 1 yr without charging with dye or electrolyte. Good long term stability of the cobalt sulphate compared to graphite was observed during this study.
Design Optimization of Shore-Based Low Temperature Thermal Desalination System Utilizing the Ocean Thermal Energy
Authors: Mutair Sami , Ikegami Yasuyuki
Published: May 2014

A model for calculation and optimization of seawater desalination process is presented. In this process, temperature difference between the upper and the lower strata of the ocean is utilized in producing fresh water, by evaporating the warm surface seawater at a reduced pressure and then condensing the generated steam by using the colder seawater drawn from the depth of the ocean to produce distilled water. In order to make the optimization process realistic, the developed model takes into consideration the characteristics of the proposed location such as temperature and density variation with depth, seabed topography, and subsequently the actual lengths of the cold and the warm seawater intake pipes. This article gives details of the process and investigates on the influence of various parameters on its economics. As electricity is the sole source of energy used, the objective function was taken as the specific energy, i.e., the amount of electrical energy required for producing a unit mass of distilled water. Results indicate that distilled water can be produced at a value as low as 5.5 kWh per ton, which makes the process competitive with most of the existing desalination technologies.