bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discrete Phase Modeling of the Powder Flow Dynamics and the Catchment Efficiency in Laser Directed Energy Deposition With Inclined Coaxial Nozzles
Authors: Alya Sachin , Singh Ramesh 
Published: January 2021

Abstract
Laser directed energy deposition (DED) is one of the most promising additive manufacturing processes for restoring high-value components. The damaged components can have complex free-form shapes, which necessitate depositions with an inclined nozzle, where the gravity can adversely affect the powder flow dynamics and the powder catchment efficiency (PCE). PCE is defined as the fraction of the total mass flowrate entering the melt pool, and a low PCE can render the process inviable. In this paper, the effect of nozzle inclination on the powder flow dynamics and resulting PCEs have been studied. It was found that the powder flow dynamics is altered significantly in an inclined nozzle and results in an asymmetric and skewed powder jet. The PCE deteriorates rapidly with an increase in the nozzle inclination due to the progressive defocusing and falls below 20% at 75 deg. A discrete phase model has been developed to understand the powder flow dynamics at different inclinations and process conditions. The mass flow distribution asymmetries on the focal plane at various nozzle inclinations have been analyzed via the model. The model can predict PCEs at different nozzle inclinations with reasonable accuracy ranging from 5.4% at 0-deg inclination to 29.2% at 45-deg inclination. The carrier gas flow, particle size, and laser diameter affect the PCE significantly and can be used to counter the enhanced powder loss at large nozzle inclinations. Process maps have been developed to identify the favorable, acceptable, and low PCE regions to select optimal DED parameters.
Two Actuation Methods for a Complete Morphing System Composed of a VGTM and a Compliant Parallel Mechanism
Authors: Xi Fengfeng , Zhao Yinjun , Wang Jieyu , Wang Wenbin , Tian Yingzhong 
Published: January 2021

Abstract
In this paper, a complete morphing system consisting of a variable geometry truss manipulator (VGTM) is presented that is fully covered by a flexible panel skin. Two approaches are studied for the morphing control. The first one is to have the VGTM act as a driving mechanism and the flexible panels as a passive system. In this case, the VGTM is composed of active members and passive lockable members. It is shown that the morphing system can reach the desired shapes through intermediate steps. The second method is to have the flexible panels act as drivers and the VGTM as a passive supporting structure. In this case, the VGTM is only composed of passive lockable members. The morphing system can also achieve the desired poses through several steps. The control strategies of the two methods are discussed along with kinematic analysis, a comparison study is conducted to show their pros and cons, two prototypes are fabricated, and experiments are carried out to verify the feasibility of two actuation methods.
Numerical Assessment of Nanofluids in Recharging Microchannel: Thermo-Hydrodynamic and Entropy Generation Analysis
Authors: Samal Sangram Kumar , Moharana Manoj Kumar 
Published: January 2021

Abstract
Three-dimensional numerical study is presented in this work that deals with thermo-hydrodynamic and entropy generation analysis of water-based nanofluids in recharging microchannel (RMC). Four different water-based nanofluids (Al2O3, CuO, SiO2, and ZnO) are considered with volume concentrations of 1–5% and nanoparticle diameters of 10–50 nm to understand their effect on thermo-hydrodynamic performance and entropy generation. Substrate bottom surface is subjected to a constant wall heat flux of 100 W/cm2 while coolant with Reynolds number range of 100–500 flows through the RMC. It is revealed that among all the nanofluids under investigation, water/Al2O3 provides enhanced thermal performance with higher effectiveness parameter (η), and it also shows reduced entropy generation. With increasing volume concentration of water/Al2O3 nanofluid, heat transfer coefficient increases, effectiveness parameter increases, and entropy generation reduces. Water/Al2O3 nanofluid with smaller nanoparticle diameter shows enhanced heat transfer coefficient and reduced entropy generation, whereas it shows decreased effectiveness parameter. This is attributed to increased pressure drop with decreasing particle diameter. This study suggests that an optimized combination of particle diameter and volume concentration should be chosen for using nanofluid-based coolants for high heat flux removal.
Multibody Dynamics on Differentiable Manifolds
Authors: Haug Edward J. 
Published: January 2021

Abstract
Topological and vector space attributes of Euclidean space are consolidated from the mathematical literature and employed to create a differentiable manifold structure for holonomic multibody kinematics and dynamics. Using vector space properties of Euclidean space and multivariable calculus, a local kinematic parameterization is presented that establishes the regular configuration space of a multibody system as a differentiable manifold. Topological properties of Euclidean space show that this manifold is naturally partitioned into disjoint, maximal, path connected, singularity free domains of kinematic and dynamic functionality. Using the manifold parameterization, the d'Alembert variational equations of multibody dynamics yield well-posed ordinary differential equations of motion on these domains, without introducing Lagrange multipliers. Solutions of the differential equations satisfy configuration, velocity, and acceleration constraint equations and the variational equations of dynamics, i.e., multibody kinematics and dynamics are embedded in these ordinary differential equations. Two examples, one planar and one spatial, are treated using the formulation presented. Solutions obtained are shown to satisfy all three forms of kinematic constraint to within specified error tolerances, using fourth-order Runge–Kutta numerical integration methods.
Experimental Characterization of an Active Infrared Thermography Heat Source
Authors: Giron-Palomares Benjamin , Hernandez-Guerrero Abel , Romero Mendez Ricardo , Yang Hai Jie 
Published: January 2021

Abstract
Accurate knowledge of the heat flux characteristics provided by optical heat sources of long heating time nondestructive infrared thermography techniques is essential to determine the adequate application of such techniques; however, detailed characterizations are scarce. Therefore, a thermal and statistical characterization of a halogen lamp was developed. A highly repeatable experimental procedure was used to characterize the heat flux generated at an ideal inspection sample top surface. The characteristics studied were: lamp distance, bulb color, lamp orientation, heat quality, and heating time. The heat flux was determined by using the readings of temperature and heat flux from the sample back, and a finite differences lumped capacitance thermal model. Detailed studies using three sensors determined that the heat flux was nonuniform (13% maximum variation). Therefore, a full quantitative characterization of the lamp was developed by using the average of such sensor readings, determining that: this halogen lamp can provide consistent top heat fluxes (although not uniformly distributed) adequate for nondestructive testing infrared thermography, the lamp distance and bulb color affected the amount of heat provided as well as the heat flux uniformity, and lamp orientation did not affect the mean top heat fluxes. This research approach can be used to determine an approximation of the lamp time-averaged heat fluxes for any material with similar top surface optical characteristics. Moreover, the technical data provided are useful to determine the adequacy of heating time, lamp distance, lamp orientation, and bulb color for long heating time nondestructive testing infrared thermography.
Electrochemical Performance of Carbon Nanofibers/Cobalt Ferrite (CNF/CoFe2O4) Composites Synthesized by Two Approaches
Authors: Atram Rounak R. , Mangate Nutan V. , Atram Ramdas G. , Kondawar Subhash B. 
Published: January 2021

Abstract
In this paper, we report the fabrication of activated carbon nanofibers/cobalt ferrite (CNF/CoFe2O4) composites by electrospinning and hydrothermal methods for comparative study of electrochemical properties. The structural, morphological, and compositional analyses of the synthesized composites were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy. CNF/CoFe2O4 electrodes were investigated for electrochemical behavior using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge (GCD). The results showed that hydrothermally synthesized CNF/CoFe2O4 composite exhibited the specific capacitance 188.36 F/g, whereas electrospun CNF/CoFe2O4 composite resulted the specific capacitance 106.59 F/g at lowest current density 0.5 A/g. 80% capacitance retention of CNF/CoFe2O4 prepared by hydrothermal as compared with 60% capacitance retention of CNF/CoFe2O4 prepared by electrospinning. These results concluded that CNF/CoFe2O4 electrode obtained by hydrothermal exhibited comparatively excellent electrochemical performance and found its suitability as electrodes for supercapacitors.
Analysis on the Inception of the Magnetohydrodynamic Flow Instability in the Annular Linear Induction Pump Channel
Authors: Ruijie Zhao , Xiaohui Dou , Qiang Pan , Desheng Zhang , van Esch B. P. M. (Bart) 
Published: January 2021

Abstract
Flow instability is the intricate phenomenon in the annular linear induction pump (ALIP) when the pump runs at off-design working condition. A three-dimensional (3D) numerical model is built to simulate the flow in the pump channel. The pump heads at different flow rates are accurately predicted by comparing with experiment. The simulation results show the fluid velocity is circumferentially nonuniform in the pump channel even at the nominal flow rate. The flow in the middle sector continuously decelerates to nearly zero with the reducing flow rate. Reversed flow occurs in the azimuthal plane, followed by vortex flow. The reason for the heterogeneous velocity field is attributed to the mismatch between nonuniform Lorentz force and relatively even pressure gradient. It is seen that the flow in the region of small Lorentz force has to sacrifice its velocity to match with the pressure gradient. An analytic expression of the axial Lorentz force is then developed and it is clearly demonstrated the Lorentz force could be influenced by the profiles of velocity and radial magnetic flux density. The coupling between velocity and magnetic field is studied by analyzing the magnitudes of different terms in the dimensionless magnetic induction equation. It is found the dissipation term is determined by not only the magnetic Reynolds number but also the square of wave number of the disturbance in each direction. The smaller disturbing wave number weakens the dissipating effect, resulting in the larger nonuniform magnetic field and axial Lorentz force.
Association between human papillomavirus vaccination and serious adverse events in South Korean adolescent girls: nationwide cohort study
Authors: Yoon Dongwon , Lee Ji-Ho , Lee Hyesung , Shin Ju-Young 
Published: January 2021

Abstract

Objective
To evaluate the association between human
papillomavirus (HPV) vaccination and serious
adverse events in adolescent girls in South
Korea.

Design
Cohort study.

Setting
A large linked database created by linking the
Korea Immunization Registry Information System and
the National Health Information Database, between
January 2017 and December 2019.

Participants
441 399 girls aged 11-14 years who had been
vaccinated in 2017: 382 020 had been vaccinated
against HPV and 59 379 had not been vaccinated
against HPV.

Main outcome measures
Outcomes were 33 serious adverse events,
including endocrine, gastrointestinal,
cardiovascular, musculoskeletal, haematological,
dermatological, and neurological diseases. A
cohort design was used for the primary analysis
and a self-controlled risk interval design for the
secondary analysis; both analyses used a risk
period of one year after HPV vaccination for each
outcome. Incidence rate and adjusted rate ratios
were estimated using Poisson regression in the
primary analysis, comparing the HPV vaccinated
group with the HPV unvaccinated group, and
adjusted relative risks were estimated using
conditional logistic regression in the secondary
analysis.

Results

Among the 33 predefined serious adverse events,
no associations were found with HPV vaccination in
the cohort analysis, including Hashimoto’s
thyroiditis (incidence rate per 100 000 person
years: 52.7
v
36.3 for the
vaccinated and unvaccinated groups; adjusted rate
ratio 1.24, 95% confidence interval 0.78 to 1.94)
and rheumatoid arthritis (incidence rate per
100 000 person years: 168.1
v
145.4 for the vaccinated and unvaccinated groups;
0.99, 0.79 to 1.25), with the exception of an
increased risk observed for migraine (incidence
rate per 100 000 person years: 1235.0
v
920.9 for the vaccinated and
unvaccinated groups; 1.11, 1.02 to 1.22).
Secondary analysis using self-controlled risk
intervals confirmed no associations between HPV
vaccination and serious adverse events, including
migraine (adjusted relative risk 0.67, 95%
confidence interval 0.58 to 0.78). Results were
robust to varying follow-up periods and for
vaccine subtypes.

Conclusions
In this nationwide cohort study, with more than
500 000 doses of HPV vaccines, no evidence was
found to support an association between HPV
vaccination and serious adverse events using both
cohort analysis and self-controlled risk interval
analysis. Inconsistent findings for migraine
should be interpreted with caution considering its
pathophysiology and the population of
interest.
Educational strategies to enhance EBM teaching and learning in the workplace: a focus group study
Authors: Welink Lisanne , de Groot Esther , Damoiseaux Roger , Bartelink Marie-Louise 
Published: January 2021

Objectives
This study aimed to gather and synthesise educational strategies that can improve teaching and learning of evidence-based medicine (EBM) in the workplace, and make them concrete by listing ideas for implementing these strategies. Insight into current workplace-based EBM teaching and learning in general practice was the starting point to generate these strategies and ideas.

Design
Exploratory, qualitative focus group study, applying the consensus method of the nominal group technique.

Setting
Postgraduate medical education; general practitioner (GP) specialty training at University Medical Centre Utrecht, the Netherlands

Participants
33 GPs and 17 GP trainees, divided in four focus groups. Using opportunistic sampling, participants were selected from the GP workplace because of their role as supervisor or trainee.

Main outcomes
An overview of educational strategies and ideas on how to implement these strategies in the workplace, followed by the participants’ global ranking of the most useful ideas.

Results
The supervisors and trainees generated a list of educational improvement strategies that can be applied in learning conversations, while observing each other’s consultations, and in (multidisciplinary) learning opportunities in the workplace. Table 1 presents the educational strategies and suggestions for implementing them. Ideas regarded as most useful include taking turns to conduct consultations and observing the other, holding a structured, in-depth discussion after observation, preparing and discussing articles found in relevant journals and on-the-spot searching for relevant evidence during learning conversations.

Conclusions
Participants provided an extensive list of educational strategies and ideas on how to implement EBM learning in daily practice. As a great deal of GP training takes place in clinical practice, supervisors and trainees could apply the suggested ideas to enhance EBM teaching and learning in the workplace.
Public awareness of the National Suicide Prevention Lifeline following the release of a hip-hop song
Authors: Torgerson Trevor , Swayze Cole , Sanghera Sara , Cooper Craig , Beaman Jason , Hartwell Micah , Vassar Matt 
Published: January 2021

Objective
In light of the current national mental health crisis, we use Google Trends, Twitter and data obtained from the National Suicide Prevention Lifeline to evaluate the effect of ‘1-800-273-8255’ on public awareness for the National Suicide Prevention Lifeline.

Design
Cross-sectional analysis.

Main outcome measures
We extracted data from Google Trends and Twitter for terms related to suicide following the release of Logic’s song, ‘1-800-273-8255’. We then used a forecasting autoregressive integrated moving algorithm model to determine the greater than expected search interest.

Results
Google searches for ‘Suicide Hotline’ increased 49% more than expected the day after Logic’s song was released and sustained increase of queries resulted in an average relative search volume of 59.5%–9.1% higher than the mean forecasted value of 50.4% for the 28 days following the release. Tweets that engaged with the account ‘@800 273talk’ on Twitter increased by 10 450% more than expected the day after the song was released and increased by a mean of 1497% greater than expected the week after the songs released.

Conclusion
Findings from our study suggest that the entertainment industry can play an important role in increasing awareness of hotline numbers. Logic’s song provides an example of a positive influence on public health and provides support for further development and standards for proper awareness of suicide in the public view.
Words matter: political and gender analysis of speeches made by heads of government during the COVID-19 pandemic
Authors: Dada Sara , Ashworth Henry Charles , Bewa Marlene Joannie , Dhatt Roopa 
Published: January 2021

BackgroundThe COVID-19 pandemic has put a spotlight on political leadership around the world. Differences in how leaders address the pandemic through public messages have practical implications for building trust and an effective response within a country.MethodsWe analysed the speeches made by 20 heads of government around the world (Bangladesh, Belgium, Bolivia, Brazil, Dominican Republic, Finland, France, Germany, India, Indonesia, New Zealand, Niger, Norway, Russia, South Africa, Scotland, Sint Maarten, United Kingdom, United States and Taiwan) to highlight the differences between men and women leaders in discussing COVID-19. We used an inductive analytical approach, coding speeches for specific themes based on language and content.FindingsFive primary themes emerged across a total of 122 speeches on COVID-19, made by heads of government: economics and financial relief, social welfare and vulnerable populations, nationalism, responsibility and paternalism, and emotional appeals. While all leaders described the economic impact of the pandemic, women spoke more frequently about the impact on the individual scale. Women leaders were also more often found describing a wider range of social welfare services, including: mental health, substance abuse and domestic violence. Both men and women from lower-resource settings described detailed financial relief and social welfare support that would impact the majority of their populations. While 17 of the 20 leaders used war metaphors to describe COVID-19 and the response, men largely used these with greater volume and frequency.ConclusionWhile this analysis does not attempt to answer whether men or women are more effective leaders in responding to the COVID-19 pandemic, it does provide insight into the rhetorical tools and types of language used by different leaders during a national and international crisis. This analysis provides additional evidence on the differences in political leaders’ messages and priorities to inspire citizens’ adhesion to the social contract in the adoption of response and recovery measures. However, it does not consider the influence of contexts, such as the public audience, on leaders’ strategic communication approaches.
What attributes do patients prefer in a family physician? A cross-sectional study in a northern region of Portugal
Authors: Nuno Joana , Fernandes Susana , Silva Teresa Rei , Guimarães Ana Catarina , Pereira Bernardo Morais , Laureano-Alves Sara , de Sousa Isabel Cristina Vieira , Brito Dinis , Firmino-Machado João 
Published: January 2021

ObjectivesTo determine which modifiable and non-modifiable attributes patients prefer in a family physician, as well as to analyse participants’ characteristics associated with their choices.DesignCross-sectional study.SettingFamily healthcare units (FHU) in the city of Braga and Barcelos (Northern Portugal).ParticipantsAdults aged 18 years or more, enrolled in the selected FHU.Main outcome measuresThe preferred attributes were assessed with a questionnaire delivered in the FHU. These attributes included gender, age and nationality and the importance of being Portuguese, of greeting with a handshake, of welcoming in the waiting area, of using an identification badge and of wearing a white coat.ResultsA total of 556 questionnaires were included in the analysis; 66% and 58% of the participants had no preference for the gender or age of the family physician, respectively. Using a multinomial logistic regression, male participants were 3.8 times more likely to have a preference for a male physician than having no preference, in comparison to female participants (OR 3.864, 95% CI 1.96 to 7.61). More than 69% of the participants considered greeting with a handshake, using an identification badge and wearing a white coat important or very important. There was a statistically significant association between being Portuguese and the major importance given to the use of an identification badge (β=0.68, 95% CI 0.23 to 1.12).ConclusionsOur data show that modifiable attributes of the family physician (greeting, presence of an identification badge and wearing a white coat) are important for patients. Potential changes in family physician attitude in consultation could ultimately affect patient–physician relationship.