bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of neurogenic intestinal motility patterns in silver perch (Bidyanus bidyanus) that persist over wide temperature ranges
Authors: Jones Bradley S. , Keightley Lauren J. , Harris James O. , Wiklendt Lukasz , Spencer Nick J. , Dinning Phil G.
Published: December 2020

Background

Fish are increasingly being utilized as a model species for genetic manipulation studies related to gastrointestinal (GI) motility. Our aim was to identify whether patterns of GI motility in fish and the mechanisms underlying their generation are similar to those recorded from mammals (including humans).

Methods

The entire intestine was removed from euthanized adult Silver Perch (n = 11) and lesioned at the midway point to obtain two equal lengths. Proximal and distal segments were studied separately in organ baths with oxygenated Krebs solution, maintained at either 15°C (n = 5) or 25°C (n = 6). Motility was analyzed during rest, after oral infusion of Krebs solution, and after application of hexamethonium (100 µM) and tetrodotoxin (TTX) (0.6 µM).

Key Results

Antegrade and retrograde propagating contractions (PC) were recorded in all preparations. In the proximal intestine, at 15 and 25°C, retrograde PCs occurred at 2.7 [1.7–4.5] and 3.1 [1.6–6.5] times the frequency of antegrade PCs, respectively. Colder temperatures did not inhibit PC frequency. Hexamethonium did not inhibit PC, and however, TTX abolished all contractile activity.

Conclusions and Inferences

Both neurogenic antegrade and retrograde propagating contractions occur throughout the intestine of Silver Perch. However, unlike the mammalian colon, these motor patterns do not require enteric nicotinic transmission and they are not inhibited by cold temperatures (15°C). Therefore, while the GI motility patterns in Silver Perch resemble those recorded from the colon of mammals, there may be differences in the mechanisms that underlying their generation.
What is new in Chicago Classification version 4.0?
Authors: Yadlapati Rena , Pandolfino John E. , Fox Mark R. , Bredenoord Albert J. , Kahrilas Peter J.
Published: December 2020

Since publication of Chicago Classification version 3.0 in 2015, the clinical and research applications of high‐resolution manometry (HRM) have expanded. In order to update the Chicago Classification, an International HRM Working Group consisting of 52 diverse experts worked for two years and utilized formally validated methodologies. Compared with the prior iteration, there are four key modifications in Chicago Classification version 4.0 (CCv4.0). First, further manometric and non‐manometric evaluation is required to arrive at a conclusive, actionable diagnosis of esophagogastric junction (EGJ) outflow obstruction (EGJOO). Second, EGJOO, distal esophageal spasm, and hypercontractile esophagus are three manometric patterns that must be accompanied by obstructive esophageal symptoms of dysphagia and/or non‐cardiac chest pain to be considered clinically relevant. Third, the standardized manometric protocol should ideally include supine and upright positions as well as additional manometric maneuvers such as the multiple rapid swallows and rapid drink challenge. Solid test swallows, postprandial testing, and pharmacologic provocation can also be considered for particular conditions. Finally, the definition of ineffective esophageal motility is more stringent and now encompasses fragmented peristalsis. Hence, CCv4.0 no longer distinguishes between major versus minor motility disorders but simply separates disorders of EGJ outflow from disorders of peristalsis.
Comparative evaluation of one‐handed versus two‐handed mask holding techniques in children during inhalational induction of anesthesia: A randomized crossover study
Authors: Choudhry Dinesh K. , Brenn B. Randall , Sacks Karen , Lutwin‐Kawalec Malgorzata , Aaronson Nicole L. , Rahman Tariq
Published: December 2020

Background

We aimed to evaluate if two‐handed mask airway is superior to one‐handed mask airway during inhalational induction of anesthesia in children.

Methods

A randomized, two period, crossover study was performed on 60 children aged 1‐8 years, with obstructive sleep apnea due to adenotonsillar hypertrophy, scheduled for adenotonsillectomy. Children were assigned to two study sequences and one control sequence of 20 subjects each. A control sequence was added to evaluate the effect of anesthetic depth. Sequence 1: One‐handed followed by two‐handed airway, 30 seconds each; Sequence 2: two‐handed followed by one‐handed airway, 30 seconds each and Sequence 3: two‐handed airway, for 60 seconds. The work of breathing indices, phase angle, and labored breathing index were recorded using respiratory inductance plethysmography. Additional outcome measures were tidal volume, minute ventilation, and respiratory rate. A straight comparison and a crossover analysis was performed.

Results

The initial comparison revealed that one‐handed airway had greater phase angle (mean diff. 17.4; 95% confidence interval [CI] 1.07‐33.68; P = .034), greater labored breathing index (mean diff. 0.56; 95% CI 0.16‐1.04; P = .004),lower minute ventilation (mean diff. −1567; 95% CI −2695 to −5.4; P = .004),and lower tidal volume (mean diff. −39; 95% CI −2.7 to −5.4; P = .02) than two‐handed airway. On crossover analysis, within‐subject difference in the phase angle was greater during one‐handed than two‐handed airway (34.3; 95% CI 8.46‐60.14; P = .01) as was labored breathing index (mean diff. 1.2; 95% CI 0.39‐2.00; P < .0046).Minute ventilation was lower during one‐handed than two‐handed airway (mean diff. −3359; 95% CI −4363 to −2355, P < 0.0001) as was tidal volume(mean diff. −78; 95% CI −110.4 to −45.8; P < .0001).

Conclusion

In children with obstructive sleep apnea due to adenotonsillar hypertrophy, two‐handed airway provides superior airway patency that was not influenced by the anesthetic depth.
Promoting bone health in children and adolescents following solid organ transplantation
Authors: Kusumi Kirstin , Shaikhkhalil Ala , Patel Hiren P. , Mahan John D.
Published: December 2020

Solid organ transplantation in children and adolescents provides many benefits through improving critical organ function, including better growth, development, cardiovascular status, and quality of life. Unfortunately, bone status may be adversely affected even when overall status is improving, due to issues with pre‐existing bone disease as well as medications and nutritional challenges inherent post‐transplantation. For all children and adolescents, bone status entering adulthood is a critical determinant of bone health through adulthood. The overall health and bone status of transplant recipients benefits from attention to regular physical activity, good nutrition, adequate calcium, phosphorous, magnesium and vitamin D intake and avoidance/minimization of soda, extra sodium, and obesity. Many immunosuppressive agents, especially glucocorticoids, can adversely affect bone function and development. Minimizing exposure to “bone‐toxic” medications is an important part of promoting bone health in children post‐transplantation. Existing guidelines detail how regular monitoring of bone status and biochemical markers can help detect bone abnormalities early and facilitate valuable bone‐directed interventions. Attention to calcium and vitamin D supplementation, as well as tapering and withdrawing glucocorticoids as early as possible after transplant, can provide best bone outcomes for these children. Dual‐energy X‐ray absorptiometry can be useful to detect abnormal bone mass and fracture risk in this population and newer bone assessment methods are being evaluated in children at risk for poor bone outcomes. Newer bone therapies being explored in adults with transplants, particularly bisphosphonates and the RANKL inhibitor denosumab, may offer promise for children with low bone mass post‐transplantation.
Lufenuron indirectly downregulates Vitellogenin in the boll weevil females reducing egg viability
Authors: Cruz Glaucilane S. , Wanderley‐Teixeira Valéria , Antonino José Dijair , Gonçalves Gabriel G. A. , Costa Hilton N. , Ferreira Maria Clara N. , Neto Clovis L. , Alves Luiz C. , Santos Fábio André B. , Teixeira Álvaro A. C.
Published: December 2020

Lufenuron, a molecule that belongs to the chitin synthesis inhibitors group of insect growth regulators, has a still unclear mode of action, but probably it affects chitin synthesis at a post‐transcriptional level. In this work, we report the effects of lufenuron on nutrition and reproduction in adult females of Anthonomus grandis, the main neotropical cotton pest and tried to link the effects on peritrophic matrix (PM) with egg viability. After Lufenuron treatment A. grandis females presented weight loss and less accumulation of protein and lipids probably due to PM breakdown. Also, treated females produce the same quantity of eggs as the control, although eggs from lufenuron‐treated females were less viable. After morphological and histochemical analysis, we have noticed that oocytes from lufenuron‐treated females contained less protein. Finally, lufenuron‐treated females produced at least nine times less vitellogenin (AgraVg) RNA than control females. We specifically showed that lufenuron treatment caused PM disruption and it has probably led to vitellogenin (AgraVg) downregulation in females culminating in egg unviability. The effect of lufenuron on PM leads to insect malnutrition, and this malnutrition downregulates vitellogenin among other genes. This is the first work that describes and tries to correlate the lufenuron effects on adult females.
Future Proofing a Building Design using History Matching Inspired Level-set Techniques
Authors: Baker Evan , Challenor Peter , Eames Matt
Published: December 2020

How can one design a building that will be sufficiently protected against overheating and sufficiently energy efficient, whilst considering the expected increases in temperature due to climate change? We successfully manage to address this question—greatly reducing a large set of initial candidate building designs down to a small set of acceptable buildings. We do this using a complex computer model, statistical models of said computer model (emulators), and a modification to the history matching calibration technique. This modification tackles the problem of level-set estimation (rather than calibration), where the goal is to find input settings which lead to the simulated output being below some threshold. The entire procedure allows us to present a practitioner with a set of acceptable building designs, with the final design chosen based on other requirements (subjective or otherwise).
Why did some larger benthic foraminifera become so large and flat?
Authors: Hallock Pamela , Seddighi Mona
Published: December 2020

Biostromes and low‐relief bioherms, some of which are characterized by exceptionally large, flat specimens of larger benthic foraminifera, are common in Palaeogene and Miocene carbonates, most notably those deposited along the Neotethys Seaway and tropical Pacific islands. By incorporating insights from palaeoceanographic research and the biology of living larger benthic foraminifera, a scenario is proposed that can account for palaeontological and sedimentological features while augmenting previous interpretations. Sexual reproduction by gamete broadcasting is common in foraminiferal taxa, including extant Nummulitidae and Amphisteginidae. Resultant zygotes can develop into tiny, resistant, easily dispersed propagules that recruit in suitable benthic‐environmental conditions. The role of algal symbiosis in the biology of larger benthic foraminifera is well‐documented. Palaeoceanographically, such taxa proliferated during times of reduced thermal stratification of the oceans. In regions with exceptionally clear, nutrient‐depleted waters, ‘twilight‐zone’ light penetration was sufficient, at least intermittently, to support some photosynthesis. On outer‐shelf or promontory sites at depths of ca 100 to 200 m, the tiny propagules of larger benthic foraminiferal species, incorporating algal symbionts with the lowest light requirements, could have settled and recruited, growing very slowly, nourished by feeding on bacteria and the limited photosynthate produced by their algal symbionts. Under such conditions, thin microspheric individuals of one or two larger benthic foraminiferal taxa could have survived and grown slowly over several years to very large shell diameters, seldom reproducing asexually. Resulting carbonate accumulation rates would have been very slow, such that even rare disturbances by currents, major storms or internal waves could have produced evidence of winnowing and sedimentary structures. The fossil evidence of such habitats should include biostromes or possibly low‐relief bioherms of low diversity assemblages characterized by abundant, exceptionally large, flat, microspheric larger benthic foraminifera.
Deconvoluting apocarotenoid‐mediated retrograde signaling networks regulating plastid translation and leaf development
Authors: Escobar‐Tovar Lina , Sierra Julio , Hernández‐Muñoz Arihel , McQuinn Ryan P. , Mathioni Sandra , Cordoba Elizabeth , Colas des Francs‐Small Catherine , Meyers Blake C. , Pogson Barry , León Patricia
Published: December 2020

Signals originating within plastids modulate organelle differentiation by transcriptionally regulating nuclear‐encoded genes. These retrograde signals are also integral regulators of plant development, including leaf morphology. The clb5 mutant displays severe leaf morphology defects due to Apocarotenoid Signal 1 (ACS1) accumulation in the developmentally arrested plastid. Transcriptomic analysis of clb5 validates that ACS1 accumulation deregulates hundreds of nuclear genes, including the suppression of most genes encoding plastid ribosomal proteins. Herein, we order the molecular events causing the leaf phenotype associated with the accumulation of ACS1, which includes two consecutive retrograde signaling cascades. Firstly, ACS1 originating in the plastid drives inhibition of plastid translation (IPT) via nuclear transcriptome remodeling of chlororibosomal proteins, requiring light as an essential component. Subsequently, IPT results in leaf morphological defects via a GUN1‐dependent pathway shared with seedlings undergoing chemical IPT treatments and is restricted to an early window of the leaf development. Collectively, this work advances our understanding of the complexity within plastid retrograde signaling exemplified by sequential signal exchange and consequences that in a particular temporal and spatial context contribute to the modulation of leaf development.
Who starts the trade war? A theory of export controls and quid pro quo
Authors: Wang Zi , Zhou Yanling
Published: December 2020

China has been accused of its quid pro quo policy which requires multinational firms to transfer technologies in return for market access. What is less well‐known is that developed countries have imposed export controls on a large variety of high‐tech products to China. We develop a simple two‐country model to understand the motives and consequences of these nontraditional trade and FDI policies. Under certain regularity conditions, we show that the coexistence of export controls and quid pro quo is the unique Nash equilibrium in this game. Comparing to the world without policy interventions, both countries are worse off in the noncooperative equilibrium. Therefore, both countries can benefit from international cooperation on knowledge sharing.
Comparison of diameter and length of subclavian arteries to external jugular veins in variably sized dogs: A cadaveric study
Authors: Chmelovski Rachel A. , Gordon‐Evans Wanda J. , Sanchez Elise D. , Coryell Jessi L.
Published: December 2020

Objective

To evaluate the length and diameter of a left external jugular vein graft as a substitute for the left subclavian artery in the modified Blalock‐Thomas‐Taussig shunt (mBTTS) in differently sized dogs.

Study design

Cadaveric study.

Animals

Dog cadavers of three weight categories (10/group): <9.5 kg, 9.5 to 27 kg, and > 27 kg.

Methods

The length and infused external diameters of harvested vessels were measured with vernier calipers and recorded. A matched‐pairsttest was used to test the difference in vessel lengths. The agreement in vessel diameters was assessed by using Lin's concordance correlation coefficient (CCC). Pearson's correlation coefficients (CC) were determined for vessel diameter to weight category and vessel length to weight category.

Results

The external jugular vein measured longer than the subclavian artery in all dogs (52.0 ± 20.8 mm and 23.0 ± 8.9 mm, respectively), with a mean difference of 28 ± 14.3 mm (P < .001). The mean external infused subclavian and external jugular diameters measured 7.8 ± 2.2 mm and 8.0 ± 2.5 mm, respectively (P= .32). Lin's CCC was 0.87. Pearson's CC were 0.74 in both vessel diameters (P< .001); they were 0.36 and 0.43, respectively, for subclavian artery and external juglar vein length (P< .001).

Conclusion

Autologous external jugular vein grafts had an external diameter similar to subclavian artery and a significantly longer length in variably sized dogs.

Clinical significance

External jugular vein grafts may be an acceptable graft choice for mBTTS.
Concentrations of Volatile Organic Compounds in the Megacity of São Paulo in 2006 and 2011/2012 - A Comparative Study
Authors: Alvim Debora Souza , Gatti Luciana Vanni , Corrêa Sergio Machado , Chiquetto Julio Barboza , Pendharkar Jayant , Pretto Angélica , Santos Guaciara Macedo , Rossati Carlos De Souza , Herdies Dirceu Luis , Figueroa Silvio Nilo , Nobre Paulo
Published: December 2020

The focus of this study was to measure the Volatile Organic Compounds (VOCs) concentrations in the megacity – São Paulo Metropolitan Area (SPMA). The measurements analyzed in this study included 78 hydrocarbon (HC) samples collected during 2006, and 66 samples of HC, 62 of aldehydes and 42 of ethanol collected during 2011-2012. The observational results showed that the consumption of ethanol, gasoline and diesel from 2006 to 2012 increased by 64 %, 23 % and 25 %, respectively, with substantial changes in the atmospheric composition. The 10 most abundant VOCs in the atmosphere found during 2011/2012 at CETESB IPEN/USP air quality monitoring station were ethanol, acetaldehyde, formaldehyde, acetone, propane, ethene, ethane, butane, 1-ethyl-4-methyl benzene, and 1,2,4-trimethyl benzene. During the 2006 campaign, alkanes represented 54.8 % of the total HC concentration, alkenes 29.2 %, aromatics 13.6 %, and alkadienes 2.4 %. On the other hand, during the 2011-2012 campaign, aldehydes represented 35.3 % of the VOCs, ethanol 22.6 %, aromatics 15.5 %, alkanes 13.5 %, acetone 6.8 %, alkenes 6.0 %, and alkadienes with less than 0.1 %.  An increase in VOCs concentrations in the SPMA atmosphere from 2006 to 2012, such as aldehydes and aromatics (which are important ozone precursors) was measured.
Determination of CR-39 and LR-115 Type II Mean Critical Angle of Etching Using a New Monte Carlo Code
Authors: Harrass H. , Talbi A. , Touti R.
Published: December 2020

CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs) are used, in order to assess the concentration of nuclides belonging to 238U and 232Th series, and these ones can be also used to measure the contents of radon 222Rn and thoron 220Rn gases in different locations. In this paper, a Monte Carlo code was developed to calculate the mean critical angle for which alpha particles emitted from 238U and 232Th families in studied material samples reach CR-39 and LR-115 type II surfaces and bring about latent tracks on them. The dependence of the SSNTDs mean critical angle on the removed thickness and the initial alpha particle energy has been studied. A linear relationship between CR-39 mean critical angle and the initial alpha particle energy for different removed thicknesses has been found. This straightforward relationship allows determining quickly the mean critical angle of etching which corresponds to initial alpha particle energy for a given removed thickness. CR-39 mean critical angle ranged from 59 deg for an alpha particle emitted by 212Po to 71 deg for an alpha particle emitted by 232Th, for the value of removed thickness of 6 μm; whereas LR-115 type II mean critical angle does not depend on the initial alpha particle energy except for 232Th, 238U, 230Th, and 234Ra when the removed thickness ranged from 6 μm to 8 μm. Obtained data by using the current method and those obtained in the literature are in good agreement with each other.
Large Eddy Simulation of a Condensing Wet Steam Turbine Cascade
Authors: Post Pascal , Winhart Benjamin , di Mare Francesca
Published: December 2020

The influence of turbulence modeling approach by means of (U)RANS and large eddy simulation (LES) on the overall modeling of turbulent condensing wet steam flows is investigated using the example of a low-pressure steam turbine cascade. For an accurate numerical treatment of turbulence in the presence of shock waves, necessary for predictive scale-resolving computations, a hybrid flux treatment switches between a baseline nondissipative central flux in energy consistent split form and a shock-capturing upwind flux in shocked regions based on a shock sensor. Condensation is realized by a monodispersed Euler–Euler source term model, the equation of state by the highly efficient and accurate spline based table lookup method (SBTL). The numerical treatment is validated with a decay of homogeneous isotropic turbulence test case containing eddy shocklets. The measurement results of the condensing wet steam cascade are overall much better matched by LES compared to RANS and URANS. Analysis shows that the LES is much better able to account for the inherently unsteady nature of the spontaneous condensation process and its interaction with the trailing edge shock wave structure.
Development of Experimental and Numerical Methods for the Analysis of Active Clearance Control Systems1
Authors: Da Soghe Riccardo , Mazzei Lorenzo , Tarchi Lorenzo , Cocchi Lorenzo , Picchi Alessio , Facchini Bruno , Descamps Laurent , Girardeau Julian , Simon Matthieu
Published: December 2020

The ever increasing performance requirements of modern aeroengines necessitate the development of effective ways to improve efficiency and reduce losses. Casing temperature control is particularly critical from this point of view, since thermal expansion directly affects the blade tip clearance and thus the associated leakages. To limit the turbine tip flows, active clearance control (ACC) systems have been implemented over the last decades. These systems are usually based upon impingement cooling, generated by a series of perforated manifolds enclosing the turbine casing. When dealing with aeroengine low pressure turbines, the current trend in increasing the engine bypass ratio, so as to enhance the system propulsive efficiency, pushes the limits of ACC traditional design performance. The reduction of the pressure head at the ACC system inlet requires lower nozzle-to-target distances as well as denser impingement arrays to compensate the reduction of the jets' Reynolds number. Literature correlations for the impingement heat transfer coefficient estimation are then out of their confidence range and also RANS numerical approaches appear not suitable for future ACC designs. In this work, methodologies for the development of accurate and reliable tools to determine the heat transfer characteristics of low pressure ACC systems are presented. More precisely, this paper describes a custom designed finite difference procedure capable of solving the inverse conduction problem on the target plate of a test sample. The methodology was successfully applied to an experimental setup for the measurement of the thermal loads on a target plate of a representative low pressure ACC impinging system. The experimental outcomes are then used to validate a suitable numerical approach. Results show that RANS model is not able to mimic the experimental trends, while scale-resolving turbulence models provide a good reconstruction of the experimental evidences, thus allowing to obtain a correct interpretation of flow and thermal phenomena for ACC systems.
Auto-Tuning Control of Proton Exchange Membrane Water Electrolyzer With Self-Assessment and Gain Scheduling
Authors: Keow Alicia Li Jen , Chen Zheng
Published: December 2020

Proton exchange membrane (PEM) electrolyzer can produce gases at the pressure suitable for direct storage into metal hydride cylinders, bypassing compressors, and other auxiliary components. For direct storage into metal hydride containers, hydrogen gas's pressure and flowrate must be well controlled. However, the PEM electrolyzer's time-variant and nonlinear dynamics call for an adaptive control to maintain its output performance. Therefore, in this paper, a model-free relay-feedback autotuning approach is proposed to tune a proportional-integral (PI) controller online. The controller determines the voltage supply to the electrolyzer to track a certain current setpoint, which corresponds to a constant hydrogen production rate. A gain scheduling approach is developed to pick up the right controller gain at different setpoints, minimizing the tuning frequency. A self-assessment algorithm is developed to determine the situations where the autotuner should activate to update the PI parameters, thus allowing the control system to be tuned autonomously. The autotuning PI control is successfully tested with a PEM electrolyzer setup. Experiment results showed that autotuner with gain scheduling could tune the controller parameters producing a desired transient behavior and is adaptive to the variations in setpoint and operating conditions.
Onset Criteria for Bulk-Mode Thermoacoustic Instabilities in Supercritical Hydrocarbon Fuels
Authors: Hunt Steven A. , Migliorino Mario Tindaro , Scalo Carlo , Heister Stephen D.
Published: December 2020

We have investigated supercritical-p (p > 1192 psi (8.22 MPa)) methanol at pressures up to 1645 psi (11.3 MPa) flowing through a heated tube at flow rates of 4–7 lb/h (1.8–3.2 kg/h). Tube heated lengths have been varied from 4 to 6 in (10 to 15 cm), internal diameters from 0.027 to 0.069 in (0.069 to 0.175 cm), and heat inputs between zero and 800 W. Fluid temperature at the tube inlet remained subcritical (T < 464 °F (513 K)); outlet temperatures were transcritical or supercritical. Two phenomena were observed: system-wide bulk-mode oscillations and localized acoustic modes. In this study, predictive efforts are undertaken to characterize system-wide bulk-mode oscillations. The parameter space has been nondimensionalized, yielding four dimensionless variables. Stability criteria based on these dimensionless groups have been established for two separate test articles and fluids; both criteria suggest that the heat required for the onset of oscillations is proportional to the mass flow rate times the mean pressure and inversely proportional to the fuel density.
Wall-Shear-Stress-Based Conditional Sampling Analysis of Coherent Structures in a Turbulent Boundary Layer
Authors: Ryu Sangjin , Davis Ethan , Park Jae Sung , Zhang Haipeng , Yoo Jung Yul
Published: December 2020

Coherent structures are critical for controlling turbulent boundary layers due to their roles in momentum and heat transfer in the flow. Turbulent coherent structures can be detected by measuring wall shear stresses that are footprints of coherent structures. In this study, wall shear stress fluctuations were measured simultaneously in a zero pressure gradient turbulent boundary layer using two house-made wall shear stress probes aligned in the spanwise direction. The wall shear stress probe consisted of two hot-wires on the wall aligned in a V-shaped configuration for measuring streamwise and spanwise shear stresses, and their performance was validated in comparison with a direct numerical simulation result. Relationships between measured wall shear stress fluctuations and streamwise velocity fluctuations were analyzed using conditional sampling techniques. The peak detection method and the variable-interval time-averaging (VITA) method showed that quasi-streamwise vortices were inclined toward the streamwise direction. When events were simultaneously detected by the two probes, stronger fluctuations in streamwise velocity were detected, which suggests that stronger coherent structures were detected. In contrast to the former two methods, the hibernating event detection method detects events with lower wall shear stress fluctuations. The ensemble-averaged mean velocity profile of hibernating events was shifted upward compared to the law of the wall, which suggests low drag status of the coherent structures related with hibernating events. These methods suggest significant correlations between wall shear stress fluctuations and coherent structures, which could motivate flow control strategies to fully exploit these correlations.
Intermittency, Secondary Bifurcation and Mixed-Mode Oscillations in a Swirl-Stabilized Annular Combustor: Experiments and Modeling
Authors: Singh Samarjeet , Roy Amitesh , K. V. Reeja , Nair Asalatha , Chaudhuri Swetaprovo , Sujith R. I.
Published: December 2020

We experimentally study thermoacoustic transitions in an annular combustor consisting of sixteen premixed, swirl-stabilized turbulent flames. We show the changes in the characteristics of bifurcations leading to the state of longitudinal thermoacoustic instability (TAI) when equivalence ratio and bulk velocity are systematically varied. Depending upon the bulk velocity, we observe different states of combustor operation when the equivalence ratio is varied. These states include combustion noise, intermittency, low-amplitude TAI, mixed-mode oscillations (MMO), and high-amplitude TAI. We closely examine the special case of MMO that is encountered during the transition from low-amplitude TAI to high-amplitude TAI. We also discuss the global and local flame dynamics observed during the state of MMO. We find that during epochs of low-amplitude oscillations of MMO, all the flames are partially synchronized, while during epochs of high-amplitude oscillations, all the flames are perfectly synchronized. Finally, we replicate the criticalities of bifurcation of the annular combustor in a phenomenological model containing sixth-order nonlinearities.
Preliminary Design Framework for the Power Gearbox in a Contra-Rotating Open Rotor
Authors: San Benito Pastor Diana G. , Nalianda Devaiah , Sethi Vishal , Midgley Ron , Rolt Andrew , Block Novelo D. Alejandro
Published: December 2020

Geared contra-rotating open rotors have the potential to further reduce fuel consumption relative to geared turbofans, but require a more-complex speed-reducing transmission system to drive the propellers. Hitherto, the preliminary design for such transmission systems has been reported independently of the overall engine modeling or has been limited by many predetermined engine constraints. This has restricted the feasible design space of the transmission systems. A simple transmissions preliminary design approach is needed that does not involve complicated mechanical assessments and can be integrated with engine preliminary design studies. This paper presents a novel design framework for sizing a double-helical differential planetary gearbox for a contra-rotating open rotor. An up-to-date methodology is proposed for the design of maximum load capacity gears for this application based on the power-transmitted, durability, and space envelope requirements. The methodology was validated with published data, demonstrating only very minor differences in geometry dimensions. Parametric analyses have been made to assess the impact of the design assumptions on gearbox dimensions. The framework also enables the identification of feasible torque ratios between the output shafts of the speed-reducer and the contra-rotating propellers driven by them. The impact of the torque ratio on the size of the gearbox has been analyzed for equal propeller rotational speeds and different speed ratios between the output shafts. This study shows that potential torque ratios lie between 1.1 and 1.33, with the higher ratios enabling more compact gearboxes having four or five planet gears.
A Review of Tubular Conical Transition Strength Design Equations
Authors: Ku Albert , Chen Jieyan , Cyprian Bernard
Published: December 2020

This paper consists of two parts. Part one presents a thin-shell analytical solution for calculating the conical transition junction loads. Design equations as contained in the current offshore standards are based on Boardman’s 1940s papers with beam-column type of solutions. Recently, Lotsberg presented a solution based on shell theory, in which both the tubular and the cone were treated with cylindrical shell equations. The new solution as presented in this paper is based on both cylindrical and conical shell theories. Accuracies of these various derivations will be compared and checked against FEM simulations.

Part 2 of this paper is concerned with the ultimate capacity equations of conical transitions. This is motivated by the authors’ desire to unify the apparent differences among the API 2A, ISO 19902 and NORSOK design standards. It will be shown that the NORSOK provisions are equivalent to the Tresca yield criterion as derived from shell plasticity theory. API 2A provisions are demonstrated to piecewise-linearly approximate this Tresca yield surface with reasonable consistency. The 2007 edition of ISO 19902 will be shown to be too conservative when compared to these other two design standards.
Experimental Study of the Effect of the Pontoon Dimensions on the Flow-Induced Motions (FIM) of a Semi-Submersible Platform With Four Square Columns
Authors: Gonçalves Rodolfo T. , Suzuki Hideyuki , Marques Matheus A. , Silva Leandro S. P. , Tian Chenling , Hirabayashi Shinichiro
Published: December 2020

The Flow-Induced Motions (FIM) is an essential topic on multi-column platforms due to the effect on the mooring line fatigue life. Vortex-Induced Motions (VIM) or galloping behavior can be observed for an array of four columns with square sections. The presence of pontoons showed to be important for changing the flow around the array and promoting different amplitude behaviors of the motions in the transverse direction mainly. This article aims to understand the effect of the presence of four pontoons on the FIM of a semi-submersible platform (SS) with four square section columns. Model tests of a floating system supported elastically utilizing four springs were performed in a towing tank. Five different pontoon ratios were tested, namely P/L = 0, 0.25, 0.50, 0.75, and 1.00; where P is the pontoon height (the dimension in the vertical direction), and L is the length of the square column face. The draft condition was kept constant as H/L = 1.5; where H is the draft of the platform. The spacing ratio of the columns was S/L = 4; where S is the distance between column centers. Two incidence angles of the current were carried out, namely 0 and 45 degrees. The amplitudes in the transverse direction (direction perpendicular to the incidence current) decreased by increasing the pontoon ratio for 0 and 45-deg incidences. The pontoons positioned aligned to the flow significantly reduced the amplitudes in the transverse direction since the pontoon presence in this position modified the incident wake in the downstream columns. The pontoon presence needs to be well investigated to choose the best condition to avoid raising the FIM or mitigating the FIM.
Analysis of Open-Source CFD Tools for Simulating Complex Hydrodynamic Problems
Authors: Siddiqui Mohd Atif , Xu Hui-li , Greco Marilena , Colicchio Giuseppina
Published: December 2020

OpenFOAM (OF) represents an attractive and widely used open-source environment for simulating complex hydrodynamic scenarios with several implemented numerical methods and wide variety of problems it can be applied to. For commercial and open-source solvers, though, expertise and experience are required to get physical and reliable results. Here, without pretending to be exhaustive, we aim to contribute in highlighting advantages and challenges of some key computational fluid dynamics (CFD)-simulation tools, with focus on the OF platform. We examine the effect of grid type, grid size and time-evolution scheme. Dynamic-mesh techniques and their influence on local and global numerical results are discussed, as well as the use of an overset grid versus a deforming mesh. Lastly, possible error sources in CFD simulations are discussed. These numerical studies are performed investigating two complex hydrodynamic problems: 1. a fully-immersed flapping hydrofoil aimed to generate thrust, 2. a damaged and an intact ship section fixed in beam-sea waves, in forced heave and roll motion in calm water. In the first case, vortex-shedding and wake features are crucial; in the second case, free-surface flow effects play the key role while the importance of vortex-shedding and viscous-flow effects depends on the scenario. The first problem is solved with OF and validated with results from benchmark experiments. The second problem is solved using (A) OF, (B) an in-house CFD solver and (C) a fully-nonlinear potential-flow code. A and B assume laminar-flow conditions and use, respectively, a volume-of-fluid and a level-set technique to handle the free-surface evolution. C is considered to examine importance of nonlinear versus viscous effects for the examined problems. The results are compared against in-house experiments.
Simulation of Ship-Ice Interaction in Level Ice
Authors: Erceg Sandro , Ehlers Sören , von Bock und Polach Franz
Published: December 2020

This paper presents the capabilities of a ship-ice interaction simulator developed at the Hamburg University of Technology for the ship operation in level ice. Besides a brief introduction of the fundamentals of the simulator and the full availability of the source code, the capabilities of the simulator in terms of the following are presented: simulation of the local ice load distribution along the hull, simulation of the resistance in ice, simulation of the cusp size and form. In addition, and most importantly, it will be shown how these results are changing with changing geometries of the hull shape. Thus, the sensitivity to various geometric changes of the hull to the simulation results will be presented and thereby the capabilities of the simulator. In other words, this paper seeks to introduce and present a robust simulator for the ship performance in ice suitable for hull design evaluations. By doing so, the sensitivity of the simulator results will be shown for various geometric hull shapes and the results will be discussed. The findings indicate that the simulator is well suited for early and detailed design assessment of the hull shape and for general optimization of the hull for ship-ice interaction in level ice.
Experimental Study on Conductivity of Regional Sand and its Field Application
Authors: Li Minghui , Zhou Fujian , Wang Jin , Liang Tianbo , Wang Yuechun , Zhang Lufeng
Published: December 2020

Hydraulic fracturing is the most commonly used stimulation method at present. The improvement effect and validity period mainly depend on the fracture conductivity. Carbo proppant is widely used worldwide for its excellent performance in increasing the conductivity of fracture support. The proppant used in the fracturing development of the Karamay oilfield in Xinjiang is also mainly Carbo proppant, but Karamay has abundant regional sand resources due to its special geographical location and geological conditions. Compared with the high cost and transportation cost of the Carbo proppant, the available regional sand becomes cheaper and reduces the development cost. According to the evaluation standard of flow conductivity of proppant in petroleum and natural gas industry, Firstly, the basic physical properties of the regional sand in Xinjiang were evaluated through the laboratory experiment system, and compared with the Carbo proppant. Secondly, the effect of sand placement concentration (8kg, 10kg, 16kg) and mesh number of proppant (30/50, 40/70) on regional sand conductivity was studied based on the conductivity evaluation system. Finally, the effect of the combination of regional sand and Carbo proppant on the conductivity was studied, under the same sand placement concentration and mesh number of proppant. The results of laboratory experiments show that the hardness and density of regional sand are higher than that of Carbo proppant, but the sphericity of regional sand is smaller than that of Carbo proppant. Under the same sand placement concentration, the regional sand conductivity of 30/50 meshes was higher than that of 40/70 meshes. As the concentration of sand placement increases, the ability of regional sand conductivity increases. The conductivity of a 1:1 mixture of regional sand and Carbo quartz is comparable to that of all Carbo quartz. According to the application examples of adjacent Wells A and B in block X of Xinjiang oilfield, the project that the ratio of regional sand to Carbo proppant is 1:1 can guarantee stable and effective flow conductivity and save fracturing cost.
Modeling of Crack Propagation in Defective X100 Line Pipes
Authors: Xue Lufeng , Paredes Marcelo , Nonn Aida , Wierzbicki Tomasz
Published: December 2020

A comprehensive experimental program is carried out to determine material parameters for fracture initiation and propagation in X100 pipeline steels. The quadratic Hill’48 yield function along with an isotropic hardening are used to describe plastic flow at large deformation and a phenomenological fracture criterion to predict fracture initiation. Fracture mechanics SENT specimens are used to calibrate post-initiation softening parameters necessary for ductile crack propagation in thick components. Once the material model parameters set is complete a final comparison is conducted with ring expansion test on same material.
Fast Riser Installation: A Field Proven, Safe and Efficient Riser Pull-in Technology
Authors: Tian Zhigang (Kevin) , Radanovic Branka , DaSilva Otto , Kirkland Blair , Mediamolle Glenn , Cruz Pete
Published: December 2020

A technical study of an innovative steel catenary riser (SCR) installation technology is presented in this paper. This installation technology maneuvers the hull through ballasting to align its riser porch with the riser, which is philosophically different from conventional riser installation that relies on an array of tugging winches to catch and pull riser into positions of the riser porches. The technology has been applied to the installation of eight SCRs on the Delta House production semi-submersible (second end) and, subsequently, five tieback SCRs (first end). We demonstrate that equipment arrangement, riser adaptor fabrication, and ballasting process remain the same for both first end and second end operations, resulting in a robust solution for riser installation. The technology has been proven safe in operations and efficient in saving installation time and cost.

This paper focuses on the technical aspects of the riser installation technology, from concept development, technical qualification, to numerical simulations. Vessel positioning and riser-hull clearance during all steps of riser pull-in and installation, as well as planning for ballast water transfer required throughout the process, is prepared with an in-house program based on rigid body rotation. Numerical simulations are performed to identify critical stages of the riser pull-in and to examine the clearance from the pull-in wire or the riser to the hull. The dependence of the minimum clearance on a few parameters related to riser installation is determined and discussed. More numerical simulations are performed to assess the vessel motion response and its dynamic effect on riser-hull clearance and to establish environmental limits for riser installation operation. Discussions are provided for potential challenges of the technology when it is applied to different production and export risers in various water depths.
Real-Time Well Monitoring and Engineering Analysis of Drilling Activities: Intelligent Rig State Detection and Prediction With Uncertainty
Authors: Kemajou Vanessa , Samuel Robello
Published: December 2020

Drilling activities are risky and costly, especially when performed offshore. Careful monitoring and real time data analysis are required for safe and efficient operations with minimized down-time. Drilling operations, being fast-paced and not visible, often lead to transient and unforeseen issues. The synchronous assessment and prediction of drilling quality has historically been a challenge. It relies on a prompt collection, analysis and prediction of the multiple sensors data, as well as an immediate comparison to the original drilling plan. Another challenge is achieving real-time well engineering, and automatically and instantaneously providing valuable insights to the engineering and operations teams. A system was successfully developed to tackle these challenges. It is a cloud-based application, made with an event-driven streaming architecture to automatically retrieve real-time drilling data and compare it with planned data. The real-time data is automatically made available to determine the current well operation or rig state, and trigger the subsequent engineering analysis. Next, a forecast model is trained with the engineering calculation outputs and it returns predictions on these outputs while considering their inherent uncertainty. As a result, these predictions enable alerts to be sent when the system detects approaching anomalous conditions. The proposed system is a DecisionSpace® 365 cloud-native application on an open architecture. It is flexible, accessible from anywhere, can be automatically updated for continuous improvement, and can be deployed easily and quickly. It can also be extended to further applications.
Black-Box Modeling of Ship Maneuvering Motion Using System Identification Method Based on BP Neural Network
Authors: He Hong-Wei , Zou Zao-Jian
Published: December 2020

This paper deals with the black-box modeling of 3-DOF nonlinear maneuvering motion of surface ships by using system identification method based on BP neural network. A Mariner Class vessel is taken as the study object. The time series used in training and testing the network is the simulated data of a series of maneuvers, which is obtained by numerically solving the Abkowitz model using fourth-order Runge-Kutta method. A three-layer neural network is built to solve this multivariable regression fitting problem, and only one network model is trained to predict various ship maneuvers. Taking the mean squared error (MSE) as the loss function, the network’s weights are optimized by Levenberg-Marquardt (LM) algorithm effectively. The trained network is evaluated by several simulation tests, and it is shown that the network achieves good prediction ability and can predict the maneuvering motion as long as the control inputs and initial states of the ship motion are known.