Numerical study of erosion in critical components of subsea pipeline: tees vs bends

Elbows are a vulnerable part of piping systems in erosive environments. Traditionally, plugged tees are used instead of elbows when the erosion rate is high. However, the advantage of plugged tees over elbows in large-scale pipelines is unclear. A comprehensive computational fluid dynamics study was carried out to predict the erosion rate in plugged tees and elbows. A numerical method was first used for aluminium elbows and tees with available experimental data through which the accuracy of the numerical solution was verified. After validating the model, numerical modelling was used to compare the erosion rates of plugged tees and elbows in varying geometrical conditions, ranging from 0.0254 to 0.6 m diameter carbon steel pipes transmitting multiphase gas/sand flow. The effects of internal flow velocity and sand particle size on erosion rates were also investigated. The numerical results revealed that the erosion ratio between plugged tees and elbows strongly depends on the internal diameter of the pipe, the flow velocity and particle size. Hence, the influence of these parameters should be considered for proper selection of the fittings to be used. Finally, numerical modelling of erosion in two subsea jumpers outfitted with standard elbows and plugged tees was presented

A numerical study on water wetting associated with the internal corrosion of oil pipelines

Long distance pipelines are considered as the vein of the oil and gas industry on land and offshore. A well often produces water along with crude oil. The presence of water as well as dissolved gases such as CO2 and H2S introduces a serious menace of internal corrosion. It is well known that the distribution of water and oil inside the pipeline has a great influence on the corrosion rate. As a matter of fact, internal corrosion occurs when a free layer of water comes in contact with the pipe. Hence, predicting the distribution of water inside the pipe and identifying the continuous phase that directly wet the wall is of foremost importance when dealing with internal corrosion of oil pipelines. The accurate prediction of the distribution of water significantly increases the accuracy of corrosion prediction as well as the confidence regarding the integrity of the pipelines. In spite of all the great efforts toward studying different influential factors associated with the internal corrosion of steel pipelines, a large gap of knowledge is observed in predicting the water wetting. The objective of the present study is to employ a tuned two-fluid model by taking advantage of computational fluid dynamics, that is capable of predicting the distribution of water and the type of wetting (water wetting/oil wetting) at the bottom of the pipe. Furthermore, the effect of different parameters such as pipe diameter, oil density, oil viscosity and interfacial tension on the transition from water wetting to oil wetting is studied

Validation of chronic obstructive pulmonary disease recording in the Clinical Practice Research Datalink (CPRD-GOLD)

Objectives: The optimal method of identifying people with chronic obstructive pulmonary disease (COPD) from electronic primary care records is not known. We assessed the accuracy of different approaches using the Clinical Practice Research Datalink, a UK electronic health record database. Setting: 951 participants registered with a CPRD practice in the UK between 1 January 2004 and 31 December 2012. Individuals were selected for ≥1 of 8 algorithms to identify people with COPD. General practitioners were sent a brief questionnaire and additional evidence to support a COPD diagnosis was requested. All information received was reviewed independently by two respiratory physicians whose opinion was taken as the gold standard. Primary outcome measure: The primary measure of accuracy was the positive predictive value (PPV), the proportion of people identified by each algorithm for whom COPD was confirmed. Results: 951 questionnaires were sent and 738 (78%) returned. After quality control, 696 (73.2%) patients were included in the final analysis. All four algorithms including a specific COPD diagnostic code performed well. Using a diagnostic code alone, the PPV was 86.5% (77.5-92.3%) while requiring a diagnosis plus spirometry plus specific medication; the PPV was slightly higher at 89.4% (80.7-94.5%) but reduced case numbers by 10%. Algorithms without specific diagnostic codes had low PPVs (range 12.2-44.4%). Conclusions: Patients with COPD can be accurately identified from UK primary care records using specific diagnostic codes. Requiring spirometry or COPD medications only marginally improved accuracy. The high accuracy applies since the introduction of an incentivised disease register for COPD as part of Quality and Outcomes Framework in 2004

Answer Set Solving with Bounded Treewidth Revisited

Parameterized algorithms are a way to solve hard problems more efficiently, given that a specific parameter of the input is small. In this paper, we apply this idea to the field of answer set programming (ASP). To this end, we propose two kinds of graph representations of programs to exploit their treewidth as a parameter. Treewidth roughly measures to which extent the internal structure of a program resembles a tree. Our main contribution is the design of parameterized dynamic programming algorithms, which run in linear time if the treewidth and weights of the given program are bounded. Compared to previous work, our algorithms handle the full syntax of ASP. Finally, we report on an empirical evaluation that shows good runtime behaviour for benchmark instances of low treewidth, especially for counting answer sets.Comment: This paper extends and updates a paper that has been presented on the workshop TAASP'16 (arXiv:1612.07601). We provide a higher detail level, full proofs and more example

Training enhances the ability of listeners to exploit visual information for auditory scene analysis

The ability to use temporal relationships between cross-modal cues facilitates perception and behavior. Previously we observed that temporally correlated changes in the size of a visual stimulus and the intensity in an auditory stimulus influenced the ability of listeners to perform an auditory selective attention task (Maddox, Atilgan, Bizley, & Lee, 2015). Participants detected timbral changes in a target sound while ignoring those in a simultaneously presented masker. When the visual stimulus was temporally coherent with the target sound, performance was significantly better than when the visual stimulus was temporally coherent with the masker, despite the visual stimulus conveying no task-relevant information. Here, we trained observers to detect audiovisual temporal coherence and asked whether this changed the way in which they were able to exploit visual information in the auditory selective attention task. We observed that after training, participants were able to benefit from temporal coherence between the visual stimulus and both the target and masker streams, relative to the condition in which the visual stimulus was coherent with neither sound. However, we did not observe such changes in a second group that were trained to discriminate modulation rate differences between temporally coherent audiovisual streams, although they did show an improvement in their overall performance. A control group did not change their performance between pretest and post-test and did not change how they exploited visual information. These results provide insights into how crossmodal experience may optimize multisensory integration

Predictors of HIV self-testing among health workers at Nyeri Provincial Hospital in Kenya

Background: HIV self-testing is recognised as a possible option of expanding access to HIV testing and counselling (HTC). There is high demand for self testing among health workers. However, in many health facilities in Kenya, the rate of unregulated self-testing and factors influencing the practice remain unknown.Objectives: To determine the prevalence and factors influencing HIV self-testing among health workersDesign: A descriptive cross-sectional study.Setting: Nyeri Provincial Hospital, the largest public hospital in Central Kenya.Subjects: Four hundred and fourteen Health workers at Nyeri Provincial Hospital who included the following cadres: Nurses, Doctors, Clinical officers, Laboratory Technicians, Community Health Workers and HTC counsellors.Results: The proportion of self-testers were 65.8% (N=348). The significant predictors of HIV self-testing were identified as age, difficulty of conducting HIV self-test, reliability of HIV self-test results and confidence in HIV positive self-test results. Self-testers (n=229) identified factors that influenced them to self-test as: easy access to test kits, obligation to test themselves, saves time and fear of stigma. Non self-testers (n=119) identified inability to handle HIV positive results; idea of self-test scares me, fear of stigma and lack of access to test kits as factors inhibiting self-testing.Conclusions: Self-testing is highly practiced by health workers at Nyeri provincial hospital. HIV related stigma needs to be addressed. Increasing access to test kits may increase self-testing

On the joint analysis of the total discounted payments to policyholders and shareholders: Dividend barrier strategy

In the compound Poisson insurance risk model under a dividend barrier strategy, this paper aims to analyze jointly the aggregate discounted claim amounts until ruin and the total discounted dividends until ruin, which represent the insurer’s payments to its policyholders and shareholders, respectively. To this end, we introduce a Gerber–Shiu-type function, which further incorporates the higher moments of these two quantities. This not only unifies the individual study of various ruin-related quantities, but also allows for new measures concerning covariances to be calculated. The integro-differential equation satisfied by the generalized Gerber–Shiu function and the boundary condition are derived. In particular, when the claim severity is distributed as a combination of exponentials, explicit expressions for this Gerber–Shiu function in some special cases are given. Numerical examples involving the covariances between any two of (i) the aggregate discounted claims until ruin, (ii) the discounted dividend payments until ruin and (iii) the time of ruin are presented along with some interpretations.published_or_final_versio

Improve the performance of transfer learning without fine-tuning using dissimilarity-based multi-view learning for breast cancer histology images

Breast cancer is one of the most common types of cancer and leading cancer-related death causes for women. In the context of ICIAR 2018 Grand Challenge on Breast Cancer Histology Images, we compare one handcrafted feature extractor and five transfer learning feature extractors based on deep learning. We find out that the deep learning networks pretrained on ImageNet have better performance than the popular handcrafted features used for breast cancer histology images. The best feature extractor achieves an average accuracy of 79.30%. To improve the classification performance, a random forest dissimilarity based integration method is used to combine different feature groups together. When the five deep learning feature groups are combined, the average accuracy is improved to 82.90% (best accuracy 85.00%). When handcrafted features are combined with the five deep learning feature groups, the average accuracy is improved to 87.10% (best accuracy 93.00%)

Single nucleotide polymorphism detection by polymerase chain reaction-restriction fragment length polymorphism

ArticleNATURE PROTOCOLS. 2(11): 2857-2864 (2007)journal articl

Ultrahigh power and energy density in partially ordered lithium-ion cathode materials

The rapid market growth of rechargeable batteries requires electrode materials that combine high power and energy and are made from earth-abundant elements. Here we show that combining a partial spinel-like cation order and substantial lithium excess enables both dense and fast energy storage. Cation overstoichiometry and the resulting partial order is used to eliminate the phase transitions typical of ordered spinels and enable a larger practical capacity, while lithium excess is synergistically used with fluorine substitution to create a high lithium mobility. With this strategy, we achieved specific energies greater than 1,100 Wh kg–1 and discharge rates up to 20 A g–1. Remarkably, the cathode materials thus obtained from inexpensive manganese present a rare case wherein an excellent rate capability coexists with a reversible oxygen redox activity. Our work shows the potential for designing cathode materials in the vast space between fully ordered and disordered compounds