bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crying at the Florence Baptistery entrance – A testimony of a travelling Jew
Authors: Mayer Yakov Z. 
Published: October 2018

AbstractAn anonymous Jew arrived in Florence in the second half of the fifteenth century and spotted a pair of porphyry columns at the entrance of the Florence Baptistery. The spot overwhelmed the Jew, as it reminded him of the destruction of the Temple in Jerusalem, and he began to cry. Some time later he recorded his intense emotional experience in a quasi‐Zoharic homily on the margins of a manuscript of the Zohar. In this study, the homily is presented for the first time; copied, translated and contextualized. The article argues that it has to be understood as a response to the view of the Florence Baptistery entrance in its entirety – the columns surrounding Lorenzo Ghiberti’s famous ‘Porta del Paradiso’ (Gates of Paradise), with the Christian biblical images inscripted on them. Following this approach, a suggestion is made to see the homily as a Jewish reaction to the Christian use of the Old Testament during the Renaissance.
How medical students learn in primary care
Authors: Davis Katherine , Doole Emily , Cheek Colleen , Shires Lizzi 
Published: October 2018

SummaryBackgroundGeneral practice placements are important in medical education, but little is known about positive student experiences.MethodsFocus group interviews were conducted with medical students. Interview transcripts were analysed thematically and incorporated into an overarching conceptual framework.ResultsOf the 22 eligible students, 21 students participated. Students viewed positively placements where they felt part of the team, had the opportunity to practise procedural skills, learned at a level congruent to their stage and gained experience practising independently. Students were not motivated when they did not feel valued, or where learning opportunities were inconsistent with personal learning objectives.DiscussionSelf‐determination theory (SDT) proposes that when people perceive that they have more control over their learning, a sense of competence in the activities and tasks required of them, and a sense of being cared for and connected with another, they will be more likely to integrate learning and behaviour change.
ConclusionStrategies to support medical student learning in general practice are provided. Situated within the SDT framework, these findings may assist others to adopt the strategies most likely to enhance student motivation to learn.Students identified developing independence and decision‐making with graduated supervision as a positive experience
La agricultura urbana en Caracas: diagnóstico de los espacios agroproductivos desde una perspectiva socioecológica
Authors: Herrera Francisco 
Published: October 2018

El incremento de la población urbana ha acarreado dificultades para el acceso a los alimentos, lo cual ha propiciado el surgimiento del fenómeno de la agricultura urbana. En Caracas, esta práctica se ha manifestado con la aparición de unidades de producción agrícola. El presente estudiocomprende un diagnóstico multidimensional que sugiere relaciones entre factores económicos, sociales y ecológicos, que se perfilan como aspectos determinantes de soberanía y sustentabilidad en trece unidades. Asimismo, se localizan varias fortalezas de dicha estructura, entre las cuales se sitúan la organización social, la diversidad cultural y el acceso a políticas públicas. En tanto, sus limitantes se centran en el acceso asemillas y la poca diversidad de rubros y prácticas. En suma, el diagnóstico expuesto representa un aporte metodológico para el seguimiento de unidades de agricultura urbana.
Cultura y conservación in situ de tubérculos andinos marginados en agroecosistemas de Boyacá: un análisis de su persistencia desde la época prehispánica hasta el año 2016
Authors: Clavijo Ponce Neidy Lorena 
Published: October 2018

Con base en una indagación histórica, que tiene como complementada el estudio de caso de dos municipios del departamento de Boyacá, el presente estudio se propone identificar varios elementos culturales relacionados con tres especies andinas marginadas (Oxalis tuberosa Molina), (Tropaelum tuberosum Ruíz & Pavón) y (Ullucus tuberosus Caldas), los cuales surgen desde la época prehispánica y se sostienen hasta elpresente. Según ese marco, las evidencias muestran un sistema de conocimiento que corresponde a las creencias y las valoraciones que se organizan en torno a estas especies. Asimismo, es notorio que dicho esquema ha permanecido constante a lo largo del tiempo, al igual que tecnologías y prácticas de cultivo e intercambio, las cuales han permanecido y no sufrido mayores modificaciones desde la época precolombina,a pesar de la embestida de la revolución verde.
Desarrollo agrario y complejidad económica: estudio de caso de una empresa agrícola de Murcia, España
Authors: Noguera-Méndez Pedro 
Published: October 2018

Desde la perspectiva de la complejidad económica se puede explicar el desarrollo a partir del proceso de acumulación de conocimiento incorporado a los bienes y servicios. A partir del estudio de la evolución de una empresa agrícola de Murcia (España), dedicada, desde 1995, a la producción, manipulación y comercialización de uva de mesa sin pepita y de su comparación con otras empresas agrícolas tradicionales, se examinan diversos conceptos de esta perspectiva; en particular la incorporación de conocimiento e información a los productos y la formación de redes tanto de personas como de empresas.
An Improved Thermal-Resistance-Capacitance Model for Vertical Single U-Tube Ground Heat Exchanger
Authors: Liao Quan , Fan Yongxiang , Zhu Xiaobo , Li Jintang 
Published: October 2018

Abstract
Based on four-thermal-resistance-capacitance network within a borehole, an improved thermal-resistance-capacitance model (TRCM), which takes into account the effect of nonuniform temperature distribution along the borehole perimeter, is proposed for vertical single U-tube ground heat exchanger. For a given geometric and physical parameters of ground heat exchanger, the numerical simulations of the conventional TRCM based on three-thermal-resistance-capacitance network within borehole, the improved TRCM based on four-thermal-resistance-capacitance network within borehole and three-dimensional (3D) finite volume computational fluid dynamics (CFD) model by using fluent software were conducted, respectively. Through the comprehensive comparisons of simulation results between these above-mentioned three models for vertical single U-tube ground heat exchanger, it could be concluded that the proposed improved TRCM could not only provide relatively high accurate results, but also remarkably decrease the solving time as compared to the benchmark 3D finite volume CFD model. Since the proposed TRCM has better performance than the one based on three-thermal-resistance-capacitance network within borehole and 3D finite volume CFD model, a new reliable and feasible TRCM for vertical single U-tube ground heat exchanger could be available for the design and optimization of ground heat exchanger, the data interpretation of thermal response test (TRT) and other applications of ground heat exchanger in real industrial engineering.
Detailed Pressure Measurements During the Transition to Rotating Stall in an Axial Compressor: Influence of the Throttling Process
Authors: Margalida Gabriel , Dazin Antoine , Joseph Pierric , Roussette Olivier 
Published: October 2018

This paper presents experimental unsteady pressure measurements gathered on a single stage axial compressor during pre-stall and transition to stall operations. The aim of this study is to analyze the transition from a stable operating point to the fully developed rotating stall regime, and more specifically, the effect of the throttling process on the development of the instabilities. To do so, experiments have been repeated leading the compressor to stall operations with various throttling speed.
On one hand, this paper analyses the effect of the throttling speed on the dynamic of the instability development from the first detection of spike type precursors to completely developed rotating stall.
On the other hand, a stall warning signal based on the correlation of the instantaneous pressure signal with a reference pressure signal is built. The influence of the location of the pressure transducer used for the warning signal is first analyzed. Then an analysis of the effect of the throttling process on the time between the warning signal and the effective stall development is proposed.
Research on the Solid-Liquid Two-Phase Flow in a Helical Groove Seal
Authors: Zhang K. , Wu D. Z. 
Published: October 2018

Hydraulic machinery is widely used in delivering solid-liquid mixing medium. The abrasion and destruction caused by sediment particles occurs on the contact interface between the contacting seal elements, which has a considerable influence on the operational stability and safety.
Helical groove seal is a type of non-contacting dynamic seal. Relied on the reversed pressure produced by the rotary sealing element, the helical groove seal could reduce or prevent the leakage. Such seal has a good performance even if there is a big clearance between the sealing elements, so helical groove seal has its unique advantage on solid-liquid mixing medium. However, the study of helical groove seal on solid-liquid mixing flow is very poor.
In this paper, the certain conception and theoretical study of helical groove seal was introduced. With the commercial software FLUENT, the 3D internal flow of the seal was presented by using multiphase flow model. Based on the method of single variable model, the seals with different helical parameters were calculated to compare the characteristics of solid-liquid two phases flow in helical groove seals with different parameters, for example, the clearance and spiral groove depth. By this way, the relationship between structure and performance of particles-mixed helical groove seals is showed clearly, then the results can be used for design of helical groove seal structure.
Numerical Investigation of Impinging-Film Heat Transfer and Flow Characteristics of Turbine Inner Casing
Authors: Tong Fujuan , Gou Wenxuan , Gao Wenjing , Li Lei , Yue Zhufeng 
Published: October 2018

An efficient cooling method for the turbine inner casing is essential with the increasing of the turbine inlet temperature. The heat transfer and flow characteristics of a coupled cooling system in the turbine inner casing part, i.e., three rows of impingement jets and film holes, have been studied numerically according to the real turbine operating conditions. Seven inclined angles of the film holes along the mainstream direction (90°, ±60°, ±45°, ±35°) and the impingement jets arrangements have been researched. The positive inclination is that the angle between the fluid flow from the film holes and the mainstream is less than 90°. Otherwise, it would be negative. The numerical validation reveals that the selected computational method can provide a good prediction of the reported experimental results of the impinging-film cooling system. Then the method has been applied in the investigation of the local/average temperature, film-cooling effectiveness, and the flow patterns on the film-cooled surface.
The results show that the inclined angle can achieve a significant improvement in the film cooling performance. With the positive inclination of film holes, the average temperature of the interaction surface between the mainstream and the turbine inner casing can decrease 50K compared with that of 90°. And the average temperature on the interaction surface with the negative inclined angle can even be reduced by more than 100K. Additionally, the average film-cooling effectiveness can be increased by up to 31.79%. Such results prove that decreasing the value of inclined angle can achieve a better heat transfer performance. Moreover, the negative inclination of film holes can improve the uniformity of the film-cooling effect. On the other hand, the influence of impingement jets arrangements on the film cooling behavior is negligible. Further analysis of the flow streamline illustrates that the coolant jet from the inclined film holes can attach to the interaction surface more firmly, which will achieve a better protection away from the high-temperature turbine gas. The research will provide direct guidance for the cooling design of the turbine inner casing and improve the thermal efficiency of the gas turbine system.
Phase Separation in Vertical Header of Microchannel Condensers: A Mechanistic Model
Authors: Li Jun , Hrnjak Pega 
Published: October 2018

Phase separation has been proven to increase performance of condensers of energy conversion systems (in vapor compression systems). Instead of conventional design, the inlet to a microchannel condenser prototype is in the middle of the height. After the first pass, in the vertical second header of the condenser, vapor phase separates from liquid phase due to gravity and sometimes other effects. In ideal case vapor should go to the top and liquid to the bottom, resulting in increased heat transfer. Due to interaction between vapor and liquid, separation is not perfect, expressed through the separation efficiency.
A mechanistic model presented in the paper is built to predict the phase separation efficiency based on force balance analysis for the liquid phase and correlations for the two-phase pressure drop. For the force balance criteria, liquid phase is divided into droplets and film and treated separately. The model captures the experimental observations first in asymptotic sense: separation efficiency can be 100% at low liquid mass flux and low vapor mass flux, but also in quantitative. Initial agreement with experiment is achieved to be within 15%.
Simulation of Coalescence and Breakup of Dispersed Water Droplets in Continuous Oil Phase
Authors: Yuan Shuxia , Dabirian Ramin , Mohan Ram S. , Shoham Ovadia 
Published: October 2018

Petroleum industry uses shear devices such as chokes, valves, orifices and pumps, which cause droplet coalescence and breakup making the downstream separation process very challenging. Droplet-droplet coalescence leads to formation of larger droplets, which accelerate the phase separation, whereas the breakup of larger droplets into smaller ones delays the separation process.
Computational Fluid Dynamic (CFD) simulations are conducted by ANSYS-Fluent software to track the droplet breakup and droplet-droplet coalescence, where the interfaces between the two phases are tracked by the Volume of Fluid (VOF) model. The material of droplet is water, while the continuous phase is oil. In this study, the effect of variables such as droplet diameter, droplet relative velocities as well as droplet motion directions on the time evolution of droplet-droplet coalescence and breakup is evaluated.
The simulation results confirm that smaller droplet collisions lead to coalescence under wide ranges of droplet relative velocities, while larger droplet collisions result in droplet breakup at higher relative velocities. During coalescence, two droplets combine into one droplet, which deform in several times from one direction to orthogonal direction until recovering its shape or breakup. In addition, the simulation results show that fastest coalescence takes place when droplet collisions occur at optimum relative velocity, whereas droplet breakup occurs at higher velocities than the optimum velocity, and delay in coalescence happens at lower velocity. Furthermore, the simulation results clearly show that droplet moving direction play an important role in the occurrence of droplet coalescence and breakup. Comparison of the simulation results with the collected experimental data from literature confirm that the simulations are capable of predicting the evolution time of the droplet coalescence and breakup with high accuracy.
Foam Breakup in CFC/GLCC© System
Authors: Dabirian Ramin , Nababan Ardian , Gavrielatos Ilias , Mohan Ram S. , Shoham Ovadia 
Published: October 2018

Foaming is a common phenomenon in the petroleum industry. Foams can be desirable for drilling applications, whereby the cutting bits are lubricated, and cuttings are carried up to the surface. However, foam can be undesirable for production operation, which hinders the gas-liquid separation process.
Experimental investigation has been conducted on foam break-up in a standalone Churn Flow Coalescer (CFC), a standalone Gas Liquid Cylindrical Cyclone (GLCC©) and a combined CFC/GLCC© system. A 1-inch Foam Characterization Rig (FCR) is utilized. The FCR is equipped with a 3-inch diameter CFC, which is connected in series to a 2-inch diameter GLCC©. A total of 30 experimental runs are conducted for both Gas Mode (GM) and Liquid Mode (LM) operations. A surfactant (SI-403) with concentration of 0.025%, superficial liquid velocities of 0.1 and 0.15 m/s and superficial gas velocities of 0.5, 1, and 1.5 m/s are used in the experiments.
The experimental results show that for the GM operation, the foam break-up in combined CFC/GLCC© system is more efficient than that in the standalone GLCC©, for the same flow conditions. Lowering the superficial gas velocity or increasing the superficial liquid velocity produce less stable foam, larger gas bubbles and lower half-life time. The outlet clear liquid flow rate (with no foam) under the LM operation increases with increasing superficial liquid velocity or decreasing superficial gas velocity. The recommended operational conditions for the CFC are at low superficial gas velocities, lower than the transition boundary to churn flow in the CFC.
Numerical Simulation of Airflow and Ellipsoidal Particle Deposition in Human Upper Respiratory Tract
Authors: Kiasadegh Morteza , Abouali Omid , Emdad Homayoun , Ahmadi Goodarz 
Published: October 2018

In this study, unsteady flow field and fibrous particle deposition in a realistic model of human upper airway system including vestibule to the end of trachea were investigated using the CFD technique. The airway passage model was constructed from the CT image of a 24 year old healthy woman.
Unsteady airflow patterns during a full breathing cycle were simulated by solving the Navier-Stokes and continuity equations. For ellipsoidal fiber trajectory analysis under cyclic breathing condition, several user defined functions (UDFs) were coupled to the ANSYS-Fluent discrete phase model (DPM). The presented formulation accounted for solving the coupled translational and rotational equations of motion of ellipsoidal fibers.
Total and regional depositions for a range of fiber sizes were evaluated. The transient particle deposition fraction was compared with those obtained from the equivalent steady flow condition. The presented results showed that the steady simulation can predict the total fibrous particle deposition during cyclic breathing with reasonable accuracy but cannot properly predict the regional deposition of particles.
Design and Multiparameter Optimization of Jet-Pumps in a Pipeline Loops Using CFD Tools
Authors: Toteff Jens , Asuaje Tovar Miguel 
Published: October 2018

Despite their low efficiency compared with centrifugal pumps, jet-pumps are highly reliable robust equipment with modest maintenance which is ideal for many applications, mostly in the oil & gas industry. For example, jet-pumps could result attractive compared to other multiphase pump systems in terms of reactivating transport lines of heavy crude oil. Nevertheless, their design method and performance analysis are rarely known in the literature and keep a high experimental component like most of the pumping equipment. Starting with a pump designed by a traditional method, this paper aims to evaluate the effect of multiple geometrical and operational variables that influence the jet-pump performance combining CFD (Computational Fluid Dynamics) simulation and optimization algorithms using commercials software (ANSYS CFX® and PIPEIT® tool). Automatically, the geometric parameters are modified according to the rules of the optimization routines seeking to maximize the flow capacity, respecting restrictions such as energy consumption.
A case study is presented for the preliminary design of a pump to boost flow capacity in a trunk line of a heavy oil field. As preliminary design all simulations were carried out using single phase water flow. With this method, it was possible to quickly evaluate around 400 geometries of jet-pumps. The geometry of the optimum final pump is consistent with other pumps reported by other works. This pump enhances the fluid capacity of the line in 17% over the traditional design for the same parameters of power or consumed energy.
Influence of Pulsating Flow on Turbine Performance Investigated by DES and PIV
Authors: Nakamura Yohei , Chinen Manato , Sakakibara Masamichi , Miyagawa Kazuyoshi 
Published: October 2018

Recently, the downsizing of engine using turbocharger attracts more and more attention. Generally speaking, a turbocharger is usually designed based on its steady performance curve. However, the operating point of a turbocharger turbine does not match the steady operating point: instead it shows hysteresis behavior because of the pulsating flow generated by the engine valves. Unfortunately, turbine efficiency drops under pulsating flow conditions, but the loss mechanisms of the turbine under these conditions are not understood. Internal flow measurements under pulsating flow are actually very difficult. In this study, the internal flow under pulsating conditions was measured using a high speed PIV (Particle Image Velocimetry) system. The loss mechanisms were investigated by experimental investigation and computational fluid dynamics (CFD). The instantaneous pressure, velocity and torque were measured using a turbine experimental apparatus at WASEDA University. To generate the pulsating flow, a pulse generator was placed upstream of the turbine: a rotational disk with holes that only lets the flow through periodically. The pulsating frequency could be changed freely by changing the rotational speed of the disk. The visualization using PIV was performed at a frequency of 1 kHz at the turbine outlet.
Many fine vortices which rotate in various directions were observed under pulsating flow. Such vortices mix in the exhaust diffuser and under low frequency flow, mixing of vortices took a long time. It was observed that one loss mechanism under unsteady conditions is the mixing of vortices at the turbine outlet.
CFD was performed using ANSYS-CFX, with approximately 10 million nodes. Turbulent flows were treated by using the Reynolds-averaged Navier-Stokes (RANS) and Detached Eddy Simulation (DES) with the SST k-ω turbulence model.
It was confirmed that the wheel and exhaust diffuser total pressure loss under pulsating flow was higher under steady flow conditions. In addition, the total pressure loss is proportional to the flow pulsation frequency. The analysis with DES agreed with the PIV results qualitatively. On the other hand, the analysis with RANS could not simulate the flow pattern at the turbine outlet.