bluuebunny/crossref_metadata_2025_split huggingface dataset:
Detection of Machinery Failure Signs From Big Time-Series Data Obtained by Flow Simulation of Intermediate-Pressure Steam Turbines
Authors: Komatsu Kazuhiko , Miyazawa Hironori , Yiran Cheng , Sato Masayuki , Furusawa Takashi , Yamamoto Satoru , Kobayashi Hiroaki 
Published: August 2021

Abstract
The periodic maintenance, repair, and overhaul (MRO) of turbine blades in thermal power plants are essential to maintain a stable power supply. During MRO, older and less-efficient power plants are put into operation, which results in wastage of additional fuels. Such a situation forces thermal power plants to work under off-design conditions. Moreover, such an operation accelerates blade deterioration, which may lead to sudden failure. Therefore, a method for avoiding unexpected failures needs to be developed. To detect the signs of machinery failures, the analysis of time-series data is required. However, data for various blade conditions must be collected from actual operating steam turbines. Further, obtaining abnormal or failure data is difficult. Thus, this paper proposes a classification approach to analyze big time-series data alternatively collected from numerical results. The time-series data from various normal and abnormal cases of actual intermediate-pressure steam-turbine operation were obtained through numerical simulation. Thereafter, useful features were extracted and classified using K-means clustering to judge whether the turbine is operating normally or abnormally. The experimental results indicate that the status of the blade can be appropriately classified. By checking data from real turbine blades using our classification results, the status of these blades can be estimated. Thus, this approach can help decide on the appropriate timing for MRO.
Reducing Uncertainty in the Onset of Combustion Instabilities Using Dynamic Pressure Information and Bayesian Neural Networks
Authors: McCartney Michael , Sengupta Ushnish , Juniper Matthew 
Published: August 2021

Abstract
Modern low-emission combustion systems with improved fuel-air mixing are more prone to combustion instabilities and, therefore, use advanced control methods to balance minimum NOx emissions and the presence of thermoacoustic combustion instabilities. The exact operating conditions at which the system encounters an instability are uncertain because of sources of stochasticity, such as turbulent combustion, and the influence of hidden variables, such as unmeasured wall temperatures or differences in machine geometry within manufacturing tolerances. Practical systems tend to be more elaborate than laboratory systems and tend to have less instrumentation, meaning that they suffer more from uncertainty induced by hidden variables. In many commercial systems, the only direct measurement of the combustor comes from a dynamic pressure sensor. In this study, we train a Bayesain Neural Network to predict the probability of onset of thermoacoustic instability at various times in the future, using only dynamic pressure measurements and the current operating condition. We show that on a practical system, the error in the onset time predicted by the Bayesain Neural Networks is 45% lower than the error when using the operating condition alone and more informative than the warning provided by commonly used precursor detection methods. This is demonstrated on two systems: (i) a premixed hydrogen/methane annular combustor, where the hidden variables are wall temperatures that depend on the rate of change of operating condition, and (ii) full-scale prototype combustion system, where the hidden variables arise from differences between the systems.
Numerical Study of Boiling Heat Transfer Around Horizontal and Inclined Cylinders
Authors: Saha Avik , Das Arup Kumar 
Published: August 2021

AbstractPool boiling around a heated cylinder having a diameter larger than the departure diameter of bubbles has been simulated numerically. Thermally uniform heat flux condition has been maintained at the outer surface of the cylinder, submerged at saturated water at atmospheric pressure. Using the volume of fluid type framework of liquid phase fraction in the domain, bubble life cycle around the horizontal cylinder has been analyzed to understand different stages of growth, sliding, merging prior to departure. An effort has also been made to characterize the bubble population, emerging from different sites over the cylindrical surface. The influence of cylinder inclination along its axis on these interfacial features has also been discussed using representative numerical simulation. Temperature profiles of the cylinder surface have been portrayed for both horizontal and inclined situations before presenting respective heat transfer coefficients.
Analytical Investigation of Non-Fourier Bioheat Transfer in the Axisymmetric Living Tissue Exposed to Pulsed Laser Heating Using Finite Integral Transform Technique
Authors: Kishore Pankaj , Kumar Sumit 
Published: August 2021

Abstract
This article proposes the closed-form solution of the generalized non-Fourier model-based bioheat transfer equation (BHTE) in Cylindrical coordinates to understand the thermal behavior of living tissue heated by a pulsed laser. The axisymmetric living tissue exposed to the non-Gaussian temporal profile of laser heating has been considered to investigate the non-Fourier bioheat transfer phenomena. The closed-form solution of the generalized non-Fourier model-based BHTE with time-dependent thermal energy generation has been obtained through the finite integral transform (FIT) technique. The analytical solution was juxtaposed to the corresponding numerical solution in order to determine its reliability. The numerical solution of the aforementioned governing equation has been obtained by the finite volume method (FVM). The results of both analytical and numerical solutions have been verified using results given in published literature. Subsequently, the dual-phase-lag (DPL) model's findings were juxtaposed to those obtained using the hyperbolic and traditional Fourier models. The effect of different parameters like relaxation times corresponding to the temperature gradient and heat flux, metabolic energy generation, and blood perfusion on the resultant temperature distribution inside the axisymmetric living tissue exposed to pulsed laser heating has been discussed. The importance of this study might be found in various applications such as laser-based-photothermal therapy, melting of the surface of metal and alloys by laser heating.
Scalable Thermal Simulation of Powder Bed Fusion
Authors: Zhang Yaqi , Shapiro Vadim , Witherell Paul 
Published: August 2021

Abstract
Powder bed fusion (PBF) has become a widely used additive manufacturing (AM) technology to produce metallic parts. In PBF, thermal field evolution during the manufacturing process plays an important role in determining both geometric and mechanical properties of the fabricated parts. Thermal simulation of the PBF process is computationally challenging due to the geometric complexity of the manufacturing process and the inherent computational complexity that requires a numerical solution at every time increment of the process. We propose a new thermal simulation of the PBF process based on the laser scan path. Our approach is unique in that it simulates the thermal history of the process on the discretization of the geometry implied by the process plan (i.e., scan path), as opposed to voxelization or meshing of the design geometry. The discretization is based on the laser scan path, and the thermal model is formulated directly in terms of the manufacturing primitives. An element growth mechanism is introduced to simulate the evolution of the melt pool during the manufacturing process. A spatial data structure, called contact graph, is used to represent the discretized domain and capture all thermal interactions during the simulation. The simulation is localized through exploiting spatial and temporal locality. This limits the need to update to at most a constant number of elements at each time-step, which implies that the proposed simulation not only scales to handle three-dimensional (3D) printed components of arbitrary complexity but also can achieve real-time performance. The simulation is fully implemented and validated against experimental data and other simulation results.
Proposal of a Machining Test to Evaluate Dynamic Synchronization Error of Rotary and Linear Axes With Reversal of Rotation Direction
Authors: Li Qingzhao , Ibaraki Soichi , Wang Wei 
Published: August 2021

Abstract
The five-axis machining of a free-form surface often contains the reversal of a rotary axis’ rotation direction with linear axis synchronized with it. This paper proposes a new machining test to quantitatively evaluate the influence of the reversal of rotation direction on the surface geometry and roughness. In the five-axis machining, the trajectory of tool position and orientation is first given in the workpiece coordinate system (WCS) by the computer-aided manufacturing (cam) software, and the computerized numerical control (CNC) system converts it to the machine coordinate system (MCS) to calculate command trajectories. This paper clarifies that the tool path smoothing in the MCS can potentially cause a large contour error because of the dynamic synchronization error of rotary and linear axes. Although some academic works in the literature presented the smoothing in the WCS, many commercial CNC systems still employ the smoothing in the MCS, partly because machine tool users or makers do not clearly see how significant this influence can be on the machining accuracy. The proposed machining test enables a user to quantitatively evaluate it. The machining experiment shows that the geometric error of the finished test piece was as large as 0.16 mm under the conventional smoothing in a commercial CNC system, which can be significantly larger than the influence of other typical geometric errors of a five-axis machine tool. This paper shows, by numerical simulation, that the smoothing in the WCS can completely eliminate this contour error.
Effect of Shock Wave Behavior on Unsteady Aerodynamic Characteristics of Oscillating Transonic Compressor Cascade
Authors: Gan Jiuliang , Watanabe Toshinori , Himeno Takehiro 
Published: August 2021

Abstract
The unsteady behavior of the shock wave was studied in an oscillating transonic compressor cascade. The experimental measurement and corresponding numerical simulation were conducted on the cascade with different shock patterns based on influence coefficient method. The unsteady pressure distribution on blade surface was measured with fast-response pressure-sensitive paint (PSP) to capture the unsteady aerodynamic force as well as the shock wave movement. It was found that the movement of shock waves in the neighboring flow passages of the oscillating blade was almost antiphase between the two shock patterns, namely, the double shocks pattern and the merged shock pattern. It was also found that the amplitude of the unsteady pressure caused by the passage shock wave was very large under the merged shock pattern compared with the double shocks pattern. The stability of blade vibration was also analyzed for both shock patterns including three-dimensional flow effect. These findings were thought to shed light on the fundamental understanding of the unsteady aerodynamic characteristics of oscillating cascade caused by the shock wave behavior.
Flocking Control of Multi-Agent Systems With Permanent Obstacles in Strictly Confined Environments
Authors: Wang Fengchen , Chen Yan 
Published: August 2021

Abstract
Considering the application of flocking control on connected and automated vehicle (CAV) systems, the persistent interactions between CAVs (flocking agents) and road boundaries (permanent obstacles) are critical due to flocking constraints in a strictly confined environment. However, the existing flocking theories attempt to model and animate natural flocks by considering temporary obstacles, which only describe interactions between agents and obstacles that would eventually disappear during flocking. This paper proposes a novel flocking control algorithm to extend existing flocking theories and guarantee the desired flocking coordination of multi-agent systems (e.g., CAV systems) with permanent obstacles (constraints). By analyzing comprehensive behaviors of flocks via Hamiltonian functions, a zero-sum obstacle condition is developed to ensure the satisfaction of permanent obstacle avoidance. Then, an additional control term representing the resultant forces of permanent obstacles is introduced to tackle interactions between agents and permanent obstacles. Demonstrated and compared through simulation results, a CAV system steered by the proposed flocking control protocol can successfully achieve the desired flocking behaviors with permanent obstacles avoidance in a three-lane traffic environment, which is failed by existing flocking control theories solely considering temporary obstacles.
Associations between systemic health and retinal nerve fibre layer thickness in preterm infants at 36 weeks postmenstrual age
Authors: Shen Liangbo L , Mangalesh Shwetha , Michalak Suzanne M , McGeehan Brendan , Sarin Neeru , Finkle Joanne , Winter Katrina P , Tran-Viet Du , Benner Eric J , Vajzovic Lejla , Freedman Sharon F , Younge Noelle , Cotten C Michael , El-Dairi Mays , Ying Gui-Shuang , Toth Cynthia 
Published: August 2021

Background/aimsNeonatal insults from systemic diseases have been implicated in the pathway of impaired neurodevelopment in preterm infants. We aimed to investigate the associations between systemic health factors and retinal nerve fibre layer (RNFL) thickness in preterm infants.MethodsWe prospectively enrolled infants and imaged both eyes at 36±1 weeks postmenstrual age (PMA) using a hand-held optical coherence tomography system at the bedside in the Duke intensive care nurseries. We evaluated associations between RNFL thickness and 29 systemic health factors using univariable and multivariable regression models.Results83 infants with RNFL thickness measures were included in this study. Based on the multivariable model, RNFL thickness was positively associated with infant weight at imaging and was negatively associated with sepsis/necrotising enterocolitis (NEC). RNFL thickness was 10.4 µm (95% CI −15.9 to −4.9) lower in infants with than without sepsis/NEC in the univariable analysis (p<0.001). This difference remained statistically significant after adjustment for confounding variables in various combinations (birth weight, birthweight percentile, gestational age, infant weight at imaging and growth velocity). A 250 g increase in infant weight at imaging was associated with a 3.1 µm (95% CI 2.1 to 4.2) increase in RNFL thickness in the univariable analysis (p<0.001).ConclusionsLow infant weight and sepsis/NEC were independently associated with thinner RNFL in preterm infants at 36 weeks PMA. To our knowledge, this study is the first to suggest that sepsis/NEC may affect retinal neurodevelopment. Future longitudinal studies are needed to investigate this relationship further.
Association between race and maladaptive concentric left ventricular hypertrophy in American-style football athletes
Authors: Tso Jason V , Turner Casey G , Liu Chang , Galante Angelo , Gilson Carla R , Clark Craig , Taylor Herman A , Quyyumi Arshed A , Baggish Aaron L , Kim Jonathan H 
Published: August 2021

ObjectivesAmerican-style football (ASF) athletes are at risk for the development of concentric left ventricular hypertrophy (C-LVH), an established cardiovascular risk factor in the general population. We sought to address whether black race is associated with acquired C-LVH in collegiate ASF athletes.MethodsCollegiate ASF athletes from two National Collegiate Athletic Association Division-I programmes were recruited as freshmen between 2014 and 2019 and analysed over 3 years. Demographics (neighbourhood family income) and repeated clinical characteristics and echocardiography were recorded longitudinally at multiple timepoints. A mixed-modelling approach was performed to evaluate acquired C-LVH in black versus white athletes controlling for playing position (linemen (LM) and non-linemen (NLM)), family income, body weight and blood pressure.ResultsAt baseline, black athletes (N=124) were more often NLM (72% vs 54%, p=0.005) and had lower median neighbourhood family income ($54 119 vs $63 146, p=0.006) compared with white athletes (N=125). While both black and white LM demonstrated similar increases in C-LVH over time, among NLM acquired C-LVH was more common in black versus white athletes (postseason year-1: N=14/89 (16%) vs N=2/68 (3%); postseason year-2: N=9/50 (18%) vs N=2/32 (6%); postseason year-3: N=8/33 (24%) vs N=1/13 (8%), p=0.005 change over time). In stratified models, black race was associated with acquired C-LVH in NLM (OR: 3.70, 95% CI 1.12 to 12.21, p=0.03) and LM was associated with acquired C-LVH in white athletes (OR: 3.40, 95% CI 1.03 to 11.27, p=0.048).ConclusionsIndependent of family income and changes in weight and blood pressure, black race was associated with acquired C-LVH among collegiate ASF NLM and LM was associated with acquired C-LVH in white athletes.
Assessment of reporting quality in randomised controlled clinical trial abstracts of dental implantology published from 2014 to 2016
Authors: Knippschild Stephanie , Loddenkemper Jeremias , Tulka Sabrina , Loddenkemper Christine , Baulig Christine 
Published: August 2021

ObjectivesAccess to full texts of randomised controlled clinical trials (RCTs) is often limited, so brief summaries of studies play a pivotal role. In 2008, a checklist was provided to ensure the transparency and completeness of abstracts. The aim of this investigation was to estimate adherence to the reporting guidelines of the Consolidated Standards of Reporting Trials (CONSORT) criteria for abstracts (CONSORT-A) in RCT publications.Primary endpointAssessment according to the percentage of compliance with the 16 CONSORT-A criteria per study.Materials and methodsThis study is based on a full survey (212 RCT abstracts in dental implantology, PubMed search, publication period 2014–2016, 45 journals, median impact factor: 2.328). In addition to merely documenting ‘adherence’ to criteria, the authors also assessed the ‘complete implementation’ of the requested information where possible. The collection of data was performed independently by two dentists, and a final consensus was reached. The primary endpoint was evaluated by medians and quartiles. Additionally, a Poisson regression was conducted to detect influencing factors.ResultsA median of 50% (Q1–Q3: 44%–63%) was documented for the 16 criteria listed in the CONSORT-A statement. Nine of the 16 criteria were considered in fewer than 50% of the abstracts. ‘Correct implementation’ was achieved for a median of 43% (Q1–Q3: 31%–50%) of the criteria. An additional application of Poisson regression revealed that the number of words used had a locally significant impact on the number of reported CONSORT criteria for abstracts (incidence rate ratio 1.001, 95% CI 1.001 to 1.002).ConclusionTransparent and complete reporting in abstracts appears problematic. A limited word count seems to result in a reduction in necessary information. As current scientific knowledge is often not readily available in the form of publications, abstracts constitute the primary basis for decision making in clinical practice and research. This is why journals should refrain from limiting the number of words too strictly in order to facilitate comprehensive reporting in abstracts.
Association between body mass index and short-term mortality in patients with intra-abdominal infections: a retrospective, single-centre cohort study using the Medical Information Mart for Intensive Care database
Authors: Li Qinglin , Tong Yingmu , Liu Sinan , Yang Kaibo , Liu Chang , Zhang Jingyao 
Published: August 2021

ObjectivesThis study aimed to determine the relationship between the body mass index (BMI) and short-term mortality of patients with intra-abdominal infection (IAI) using the Medical Information Mart for Intensive Care (MIMIC-III) database.DesignRetrospective cohort study.SettingAdult intensive care units (ICUs) at a tertiary hospital in the USA .ParticipantsAdult IAI ICU patients from 2001 to 2012 in the MIMIC-III database.InterventionsIn univariate analysis, we compared the differences in the characteristics of patients in each BMI group. Cox regression models were used to evaluate the relationships between BMI and short-term prognosis.Primary and secondary outcome measures90-day survival.ResultsIn total, 1161 patients with IAI were included. There were 399 (34.4%) patients with a normal BMI (<25 kg/m2), 357 (30.8%) overweight patients (25–30 kg/m2) and 405 (34.9%) obese patients (>30 kg/m2) who tended to be younger (p<0.001) and had higher Sequential Organ Failure Assessment scores (p<0.05). The mortality of obese patients at 90 days was lower than that of patients with a normal BMI (20.74% vs 23.25%, p<0.05), but their length of stay in the ICU was higher (4.9 days vs 3.6 days, p<0.001); however, their rate of mechanical ventilation utilisation was higher (61.48% vs 56.86%, p<0.05). In the Cox regression model, we also confirmed that BMI was a protective factor in patients with IAIs, and the adjusted mortality rate of patients with a higher BMI was 0.97 times lower than that of patients with a lower BMI (p<0.001, HR=0.97, 95% CI 0.96 to 0.99).ConclusionsIAI patients with an overweight or obese status might have lower 90-day mortality than patients with a normal BMI.