bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of liver stiffness in non‐alcoholic fatty liver disease with higher fibrosis‐4 index than low cut‐off index
Authors: Tomeno Wataru , Imajo Kento , Kuwada Yukiko , Ogawa Yuji , Kikuchi Minako , Honda Yasushi , Kato Takayuki , Kessoku Takaomi , Kirikoshi Hiroyuki , Yoneda Masato , Kitahora Tetsuji , Saito Satoru , Ozawa Yukihiko , Nakajima Atsushi
Published: December 2018

Background and Aim

In the condition of high prevalence of non‐alcoholic fatty liver disease (NAFLD), a new diagnostic algorithm to efficiently identify NAFLD patients with significant fibrosis is urgently required. We evaluated the predictive ability of the fibrosis‐4 index (FIB‐4 index) for significant liver fibrosis (F ≥ 2) in a cohort of Japanese patients with NAFLD.

Methods

We prospectively calculated the FIB‐4 index in patients who were incidentally diagnosed as fatty liver in medical checkups and then conducted liver stiffness measurement by vibration‐controlled transient elastography (VCTE) only in patients in whom the FIB‐4 index was more than the low cut‐off index (> 1.45).

Results

Of the 5929 people who underwent medical checkups, a total of 1374 people were identified as having fatty liver. Among these, we performed VCTE in 106 patients in whom the FIB‐4 index was higher than 1.45. The distribution of the fibrosis stage as estimated by VCTE in the patients was as follows: F0, 52.8%; F1, 10.3%; F2, 21.6%; F3, 11.3%; and F4, 3.7%. The positive predictive value of the FIB‐4 index for detecting NAFLD with significant fibrosis was 36.6%. The minimum value of the FIB‐4 index was constant for each estimated fibrosis stage.

Conclusions

This is the first prospective study to evaluate the usefulness of the FIB‐4 index as the first step to screen NAFLD patients with significant fibrosis. In Japan, addition of one further step that combined with the FIB‐4 index is necessary to meaningfully reduce the number of patients needing liver stiffness measurement or liver biopsy.
Digital Gaming and the Arts of Parental Control in Southern Peru: Phatic Functionality and Networks of Socialization in Processes of Language Socialization
Authors: Smith Benjamin , Barad Ashley
Published: December 2018

In this article, we offer an account of the strategy that parents in southern Peru undertake to control the “excessive” gaming of their sons. With this strategy, parents attempt to reconstruct the “networks” or “channels” through which parents and sons attend to, monitor, and are made communicatively available to each another, a strategy that requires them to—among other things—disassemble competing networks of socialization. Our analysis of this ethnographic material requires us to provide a theory of the role that the “phatic function” plays in processes of language socialization. [language socialization, phatic function, digital gaming, parenting, Peru]
The Predicament of Language and Culture: Advocacy, Anthropology, and Dormant Language Communities
Authors: Schwartz Saul
Published: December 2018

A growing literature in linguistic anthropology critically examines the rhetoric of endangered language advocacy. A number of themes remain underexplored, however, including the invocation of “culture” to justify language preservation, the interests of communities without fluent heritage language speakers, and anthropology's contribution to potentially problematic advocacy tropes. Discourses like “language is the core of culture” and “when a language dies, a culture dies” are widespread in language activism even though they undermine communities’ efforts to maintain distinctive cultural identities in the wake of language shift and put dormant language communities in a double bind. While Boasian anthropology contains anti‐essentialist and counter‐nationalist perspectives on language, culture, and race, some Herderian advocacy tropes are borrowed from the (also Boasian) tradition of linguistic relativity in its popular Whorfian iteration. Drawing on my research on Chiwere language politics, I identify two forms of agency available to endangered and dormant language communities: one form of agency resists language loss but accepts dominant ideologies of national difference that make heritage languages essential to indigenous cultural identities, while another form of agency accepts language loss but resists Herderian nationalist expectations that authentic indigenous communities speak their traditional languages. [advocacy rhetoric, dormant language communities, language and culture ideologies, agency, Chiwere]
Determinants of Physical Activity for Latino and White Middle School‐Aged Children
Authors: Garcia Aileen S. , Takahashi Shinya , Anderson‐Knott Mindy , Dev Dipti
Published: December 2018

BACKGROUND

Physical activity (PA) has long been acknowledged to contribute health benefits among children. However, research has consistently shown that PA declines as children grow older. Thus, this study examined the factors which are associated to children's PA in order to identify potential barriers to PA.

METHODS

Using data from the KidQuest Program, we conducted bivariate and multivariate analyses on survey data collected from fifth to seventh grade students in a small Midwestern city.

RESULTS

We found that food knowledge, eating breakfast, and talking with family about eating healthy foods, are positively related to PA. On the other hand, screen time is negatively related to PA. In addition, our results evinced differences between ethnicities and found that Latino children's screen time affects their PA levels more than their white counterpart.

CONCLUSIONS

There are different factors which can be tapped to increase PA among middle school‐aged children. Given the differences between the Latino and white samples especially in screen time, schools should consider individualized intervention, rather than a “one size fits all” program, to increase PA participation.
School‐Based Health Centers and School Connectedness
Authors: Bersamin Melina , Coulter Robert W. S. , Gaarde Jenna , Garbers Samantha , Mair Christina , Santelli John
Published: December 2018

BACKGROUND

Improvements in health behaviors and academic outcomes have been associated with school‐based health centers (SBHCs). However, underlying mechanisms for these associations have been largely unexamined, particularly among lower‐income youth. The current study examines the relationship between SBHCs and school connectedness and whether this relationship differs by youths' socioeconomic status (SES).

METHODS

Student‐level cross‐sectional data from 503 traditional high schools in California were analyzed using multilevel regression models. California Healthy Kids Survey 2013‐2014 data included information on 3 dimensions of school connectedness and demographic characteristics including SES as measured by parental education. School‐level demographic data was gathered from publicly available sources.

RESULTS

Although no significant relationship between SBHCs and any of the school connectedness dimensions emerged, there were significant cross‐level interactions between SBHCs and parent education. SBHCs were more positively associated with school connectedness (adult caring, adult expectations, and meaningful participation) among lower SES students compared to students with higher SES.

CONCLUSIONS

SBHCs may be particularly effective in affecting school connectedness among lower income youth populations. This has wide ranging implications with regards to planning (eg, careful selection of where SBHCs can be most effective), and future research (eg, examining the effectiveness of specific SBHC strategies that support connectedness).
A Prospective Cohort Study on Injuries Among Intensely Physically Active High School Students
Authors: Krtinic Gordana , Duric Predrag
Published: December 2018

BACKGROUND

The leading cause of nonfatal injuries in age group 14‐19 is sports injuries. Purpose of the study was to determine the association between intense physical activity and injury and to identify the circumstances and environment in which injuries are most likely to occur.

METHODS

A prospective cohort study included 698 high school students 15‐19 years old, divided into those exposed and those unexposed to intense physical activity. The international standard questionnaire about physical activity (International Physical Activity Questionnaire—IPAQ) and the metabolic equivalent task (MET) scores were used.

RESULTS

The risk of injuries was 7 times higher (relative risk [RR]: 7.041; 95% confidence interval [CI]: 6.071, 8.187) and the risk of injuries requiring treatment in health facilities was 15 times higher (RR: 14.717; 95% CI: 10.652, 20.592) in the intensely physically active adolescents. The risk of gaining sports injuries was 11 times higher in the exposed group (RR: 11.212; 95% CI: 9.013, 14.074), with a significantly higher incidence rate (Inc.) among men (82.9 per 100). Most injuries occurred in football (Inc. 4.4 per 1000 hours), volleyball (Inc. 3.9 per 1000 hours), and boxing/kickboxing (Inc. 3.7 per 1000 hours).

CONCLUSIONS

Intensely physically active high school students have a much higher risk of injury, which usually occurs during training or a match.
Prevalence and Types of School‐Based Out‐of‐School Time Programs at Elementary Schools and Implications for Student Nutrition and Physical Activity
Authors: Sliwa Sarah A. , Calvert Hannah G. , Williams Heather P. , Turner Lindsey
Published: December 2018

BACKGROUND

Out‐of‐school time (OST) programs are an important setting for supporting student health and academic achievement. This study describes the prevalence and characteristics of school‐based OST programs, which can inform efforts to promote healthy behaviors in this setting.

METHODS

A nationally representative sample of public elementary schools (N = 640) completed surveys in 2013‐2014. Administrators reported on OST programs and policies at their school. Multivariable logistic regression models estimated the prevalence of school‐based OST programs, adjusting for school characteristics. Among schools with OST programs (N = 475), chi‐square tests identified school characteristics associated with having an OST policy about physical activity or nutrition.

RESULTS

Three fourths of elementary schools (75.6%) had a full‐ or partial‐year school‐based OST program, with 30.8% having both. Full‐ and partial‐year programs were significantly less prevalent in rural and township areas versus urban settings. Only 27.5% of schools with OST programs reported having physical activity and/or nutrition policies.

CONCLUSIONS

Most US elementary schools have an on‐site OST program, but disparities in access exist, and most lack policies or awareness of existing policies regarding physical activity and nutrition. To maximize OST programs' potential benefits, strategies are needed to increase access to programs and physical activity and/or nutrition policy adoption.
Dissociative state: Returned traveller with a high fever and low heart rate
Authors: Freeth Pippin , Phuong Linny K , Osowicki Joshua
Published: December 2018

See Answer
Prevalence of bacterial contamination in 50% dextrose vials in varying storage conditions after multiple punctures
Authors: Marshall K. A. , Brooks A. C. , Hammac G. K. , Thomovsky E. J. , Johnson P. A.
Published: December 2018

Objective

To determine the risk of bacterial growth in single use 50% dextrose vials punctured multiple times and stored in various hospital environments.

Materials and Methods

Three groups of three 50% dextrose vials were stored in our hospital intensive care unit at either ambient light or in a darkened drawer at room temperature or refrigerated at 4°C. One vial in each group was punctured either once, once weekly or once daily for 28 days and samples taken for bacterial culture every 7 days until completion of the project. A fourth group of three vials were inoculated with several species of bacteria and stored in our microbiology laboratory under the environmental conditions described above with cultures performed every 7 days for 28 days. In addition, the water activity of 50% dextrose was determined using commercial laboratory equipment.

Results

Scant growth of Escherichia coli and Enterobacter agglomerans was detected in cultures performed on day 7, but not subsequent time points, from the inoculated refrigerated vials. The vial punctured once daily for 28 days and stored under refrigerated conditions showed growth of Bacillus subtilis on day 28. All remaining bottles had no bacterial growth at any time point or environmental condition. The water activity of 50% dextrose was 093 at 24°C and 092 at 4°C.

Clinical Significance

Bacterial growth in 50% dextrose vials was uncommon even when inoculated with pathogens. Bacterial growth only occurred in refrigerated storage conditions. The water activity of 50% dextrose is not low enough to inhibit all bacterial and fungal growth.
Nonstationary Cointegration in the Fractionally Cointegrated VAR Model
Authors: Johansen Søren , Nielsen Morten Ørregaard
Published: December 2018

We consider the fractional cointegrated vector autoregressive (CVAR) model of Johansen and Nielsen (2012a) and make two distinct contributions. First, in their consistency proof, Johansen and Nielsen (2012a) imposed moment conditions on the errors that depend on the parameter space, such that when the parameter space is larger, stronger moment conditions are required. We show that these moment conditions can be relaxed, and for consistency we require just eight moments regardless of the parameter space. Second, Johansen and Nielsen (2012a) assumed that the cointegrating vectors are stationary, and we extend the analysis to include the possibility that the cointegrating vectors are non‐stationary. Both contributions require new analysis and results for the asymptotic properties of the likelihood function of the fractional CVAR model, which we provide. Finally, our analysis follows recent research and applies a parameter space large enough that the usual (non‐fractional) CVAR model constitutes an interior point and hence can be tested against the fractional model using a Chi‐squared‐test.
Bayesian Outlier Detection in Non‐Gaussian Autoregressive Time Series
Authors: Silva Maria Eduarda , Pereira Isabel , McCabe Brendan
Published: December 2018

This work investigates outlier detection and modelling in non‐Gaussian autoregressive time series models with margins in the class of a convolution closed parametric family. This framework allows for a wide variety of models for count and positive data types. The article investigates additive outliers which do not enter the dynamics of the process but whose presence may adversely influence statistical inference based on the data. The Bayesian approach proposed here allows one to estimate, at each time point, the probability of an outlier occurrence and its corresponding size thus identifying the observations that require further investigation. The methodology is illustrated using simulated and observed data sets.
Simultaneous identities: ethnicity and nationalism in mother tongue education in Nepal*
Authors: Pradhan Uma
Published: December 2018

The scholarly works on ethnicity and nationalism have been highly dominated by binary frameworks. In addition, the normative preference for civic consciousness and the concerns of national disintegration often separate the notions of ethnicity and nationalism. This article suggests that the notions of ethnicity and nationalism cannot be understood exclusively as a choice between maintaining the integrity of the nation and completely rejecting it. Drawing on fieldwork in mother tongue schools in Nepal, the article draws attention to the ways in which school actors discursively positioned ethnic identity as imperative to national identity, the one that bolsters the notion of Nepali nationhood. By paying close attention to the everyday context within which discourses of nationalism are situated, this article argues for an analytical necessity to approach ethnicity and nationalism in relation to each other to appreciate the process of symbolic negotiations in public spaces.
General psychological distress among Japan Self‐Defense Forces personnel dispatched on United Nations peacekeeping operations and their spouses
Authors: Tanichi Masaaki , Nagamine Masanori , Shigemura Jun , Yamamoto Taisuke , Sawamura Takehito , Takahashi Yoshitomo , Obara Asuka , Saito Taku , Toda Hiroyuki , Yoshino Aihide , Shimizu Kunio
Published: December 2018

Aim

The importance of family care during international deployment is emphasized within military organizations, but mental health interactions between deployed personnel and their spouses have not yet been assessed. This study addressed this gap by examining couples’ mental health throughout a deployment period.

Methods

The mental health of 324 spousal dyads of Japan Self‐Defense Forces personnel dispatched for a half‐year United Nations Disengagement Observer Force mission was examined, using longitudinal data derived from a survey at four time points: one‐month pre‐deployment, initial deployment, middle deployment, and immediately after homecoming. The 30‐item General Health Questionnaire was used to evaluate general psychological distress, with high scores (≥7) indicating adverse mental health.

Results

The spouses’ general psychological distress was significantly higher compared with the deployed personnel (P < 0.001). The high general psychological distress of personnel was significantly related to that of their spouses (odds ratio = 2.24; 95% confidence interval, 1.32–3.80), and vice versa (odds ratio = 2.38; 95% confidence interval 1.39–4.08).

Conclusion

Mental health care will be beneficial for not only deployed personnel but also their spouses.
Type of jealousy differentially predicts cost‐inflicting and benefit‐provisioning mate retention
Authors: Davis Adam C. , Desrochers Jessica , DiFilippo Anna , Vaillancourt Tracy , Arnocky Steven
Published: December 2018

Jealousy is argued to be an adaptive emotion that coordinates the use of mate retention acts, denoting behavior intended to guard a relationship from rivals, to prevent infidelity, and to hinder defection from the mateship. Nevertheless, few researchers have examined these relations. We sampled 144 women and men in romantic relationships and found that anxious (unease over potential infidelity) and preventive (preventing one's partner from consorting with others) but not reactive (anger over a partner being unfaithful) jealousy positively predicted cost‐inflicting mate retention. Only anxious jealousy positively predicted benefit‐provisioning acts. Sex moderated the relations between reactive jealousy with cost‐inflicting and benefit‐provisioning behavior, such that reactively jealous women used more of both kinds of mate retention.
Participation in Multiple Decision Making Water Governance Forums in Brazil Enhances Actors’ Perceived Level of Influence
Authors: Mancilla García María , Bodin Örjan
Published: December 2018

The Ecology of Games Framework (EGF) draws attention to the intertwined nature of different forums in a given policy setting and how this affects governance outcomes. In this article, we associate the EGF with the literature on power asymmetries, in order to investigate hypotheses of actors’ perceived level of influence in a forum. Focusing on the Paraíba do Sul river basin committee in Brazil, we specifically explore actors’ participation in multiple forums, time spent participating in the basin committee, and actors’ degree of involvement in the committee as factors that might explain actors’ level of perceived influence in the forum. The findings suggest participation in multiple forums is a key driver of perceived influence and thus highlight a way to challenge traditional power asymmetries. More research, however, is needed to determine to what extent perceived influence is affecting decision‐making processes and governance outcomes in the Paraíba do Sul river basin committee.
Attitude and willingness of pediatric dentists regarding dental care for children with developmental and intellectual disabilities
Authors: Abraham Simi , Yeroshalmi Farhad , Margulis Keith S. , Badner Victor
Published: December 2018

Aim

Children with developmental and/or intellectual disabilities (DD/ID) are considered to be at greater risk of developing dental disease and are more likely to have unmet dental needs than other children. The purpose of this study was to determine the attitude and willingness of pediatric dentists and residents to provide dental care for children with DD/ID.

Methods

Two surveys were created and emailed via SurveyMonkey® to pediatric dentists and post‐doctoral student members of the American Academy of Pediatric Dentistry.

Results

Five hundred and seventy‐four pediatric dentists (9%) and 143 pediatric dentistry residents (13%) responded. Ninety‐nine percent of the practicing pediatric dentists do provide dental care for children with DD/ID. Ninety‐six percent of the practitioners are confident/very confident in treating these children with nonpharmacological methods, while 86% are confident/very confident with pharmacological methods. Among the residents, 99% are willing to provide dental care to children with DD/ID after they graduate. Eighty‐six percent of the residents are confident/very confident in treating these children with nonpharmacological methods, while 70% are confident/very confident with pharmacological methods.

Conclusion

Pediatric dentist and resident respondents to the survey were overwhelmingly willing to provide dental care for patients with DD/ID and are confident with pharmacological and nonpharmacological treatment modalities.
Intimate Relationships Buffer Suicidality in National Guard Service Members: A Longitudinal Study
Authors: Blow Adrian J. , Farero Adam , Ganoczy Dara , Walters Heather , Valenstein Marcia
Published: December 2018

Objective

Members of the U.S. military are at a high suicide risk. While studies have examined predictors of suicide in the U.S. military, more studies are needed which examine protective factors for suicide. Informed by the interpersonal theory of suicide, this study examined the strength of the intimate relationship and its role as a buffer of suicidality in National Guard service members.

Method

A total of 712 National Guard residing in a Midwestern state, who had all recently returned home from a deployment, took part in this study and completed surveys at 6 and 12 months postdeployment. They were assessed on suicide risk, mental health (depression, post‐traumatic stress disorder, anxiety), and relationship satisfaction.

Results

Lower relationship satisfaction and more depressive symptoms at the 6‐month assessment were significantly related to greater suicide risk at 12 months. Each interaction between couple satisfaction and three mental health variables (PTSD, depression, and anxiety) at the 6‐month assessment was significantly associated with suicide risk at 12 months.

Conclusions

The strength of the intimate relationship serves as a buffer for suicide in National Guard service members who have PTSD, anxiety, or depression. Interventions that strengthen these intimate relationships could reduce suicide in service members.
Seven consecutive days of remote ischaemic preconditioning improves cutaneous vasodilatory capacity in young adults
Authors: Lang James A. , Kim Jahyun , Franke Warren D. , Vianna Lauro C.
Published: December 2018

Key points

Remote ischaemic preconditioning (RIPC), induced by brief bouts of ischaemia followed by reperfusion, confers vascular adaptations that protect against subsequent bouts of ischaemia; however, the effect of RIPC repeated over several days on the human microcirculation is unknown.

Using skin as a model, microvascular function was assessed at a control and a NO‐inhibited area of skin before 1 day after and 1 week after administering seven consecutive days of repeated RIPC on the contralateral arm.

Maximal vasodilatation was increased by ∼20–50% following 7 days of repeated RIPC, and this response remained elevated 1 week after stopping RIPC; however, NO‐mediated vasodilatation was not affected by the RIPC stimulus.

These data indicate that repeated RIPC augments maximal vasodilatation, but the underlying mechanism for this improvement is largely independent of NO.

This finding suggests a role for other endothelium‐derived mediators and/or for endothelium‐independent adaptations with repeated RIPC.

Remote ischaemic preconditioning (RIPC), induced by intermittent periods of ischaemia followed by reperfusion, confers cardiovascular protection from subsequent ischaemic bouts. RIPC increases conduit and resistance vessel function; however, the effect of RIPC on the microvasculature remains unclear. Using human skin as a microvascular model, we hypothesized that cutaneous vasodilatory (VD) function elicited by localized heating would be increased following repeated RIPC. Ten participants (23 ± 1 years, 6 males, 4 females) performed RIPC for seven consecutive days. Each daily RIPC session consisted of 4 repetitions of 5 min of arm blood flow occlusion interspersed by 5 min reperfusion. Before, 1 day after and 1 week after the 7 days of RIPC, two microdialysis fibres were placed in ventral forearm skin for continuous infusion of Ringer solution or 20 mM l‐NAME. Red blood cell flux was measured by laser Doppler flowmetry at each fibre site during local heating (Tloc = 39°C) and during maximal VD elicited by heating (Tloc = 43°C) and 28 mM sodium nitroprusside infusion. Data were normalized to cutaneous vascular conductance (flux/mmHg). Seven days of RIPC did not alter the nitric oxide (NO) contribution to the VD response to local heating (P > 0.05). However, the maximal VD was augmented (Pre: 2.5 ± 0.2, Post: 3.8 ± 0.5 flux/mmHg; P < 0.05) and remained elevated 1 week post RIPC (3.3 ± 0.4 flux/mmHg; P < 0.05). Repeated RIPC improves maximal VD but does not affect NO‐mediated VD in the cutaneous microvasculature. This finding suggests that other factors may explain the vasodilatory adaptations that occur following repeated RIPC.
Simulation of the Transient Thermal Response of a High Pressure Selective Catalytic Reduction Aftertreatment System for a Tier III Two-Stroke Marine Diesel Engine
Authors: Foteinos Michael I. , Konstantinidis Stavros K. , Kyrtatos Nikolaos P. , Busk Kræn Vodder
Published: December 2018

The IMO tier III legislation, applicable to vessels with a keel laying date from Jan. 1, 2016, has compelled engine builders to apply new technologies for NOx abatement. One of the most promising technologies for tier III compliance is the selective catalytic reduction (SCR) of nitrogen oxides (NOx). Despite that SCR technology has been applied in powerplants and heavy duty truck engines for years, there are challenges that stem from its applications in large two-stroke marine diesel engines. In this paper, an SCR model applicable to large two-stroke marine diesel engines is introduced. The goal of the model is to predict the thermal response of a marine SCR aftertreatment system when the engine undergoes transient loading. The model has been developed and validated using testbed measured data from a large two-stroke marine diesel engine. The output of the model is the SCR outlet temperature. It is shown that the model can accurately predict the transient inertial response of the SCR during engine acceleration, deceleration, and low load operation.
Series Active Variable Geometry Suspension Robust Control Based on Full-Vehicle Dynamics
Authors: Cheng Cheng , Evangelou Simos A.
Published: December 2018

This paper demonstrates the ride comfort and road holding performance enhancement of the new road vehicle series active variable geometry suspension (SAVGS) concept using an H∞ control technique. In contrast with the previously reported work that considered simpler quarter-car models, the present work designs and evaluates control systems using full-car dynamics thereby taking into account the coupled responses from the four independently actuated corners of the vehicle. Thus, the study utilizes a nonlinear full-car model that represents accurately the dynamics and geometry of a high performance car with the new double wishbone active suspension concept. The robust H∞ control design exploits the linearized dynamics of the nonlinear model at a trim state, and it is formulated as a disturbance rejection problem that aims to reduce the body vertical accelerations and tire deflections while guaranteeing operation inside the existing physical constraints. The proposed controller is installed on the nonlinear full-car model, and its performance is examined in the frequency and time domains for various operating maneuvers, with respect to the conventional passive suspension and the previously designed SAVGS H∞ control schemes with simpler vehicle models.
Local Stress-Field Reconstruction Around Holes in a Plate Using Strain Monitoring Data and Stress Function
Authors: Nakamura Toshiya
Published: December 2018

This study reconstructs a two-dimensional stress field from measured strain data. The advantage of using stress functions is that the stress equilibrium and strain compatibility are automatically satisfied. We use the complex stress functions given by the finite series of polynomials. Then, we find the proper set of coefficients required to make the best fit to the measured strain data. Numerical examples represent the stress concentration problems around a hole(s) in a plate. It is demonstrated that the present method reconstructs the stress field around the hole(s), and the estimated stress agrees with the finite element (FE) analysis result.
Investigation of the State Transition and Moving Boundary in a Pneumatic–Hydraulic Coupled Dielectric Elastomer Actuator
Authors: Chen Liyuan , Chen Weijia , Xue Yaoting , Zhang Mingqi , Chen Xiangping , Cao Xunuo , Zhang Zhen , Li Guorui , Li Tiefeng
Published: December 2018

Compared to robots and devices made of rigid components, soft robots and flexible devices driven by soft active materials possess various advantages including high adaptability under extreme environment and compatibility with a human. Dielectric elastomer (DE) membrane, which is commonly used in building soft actuators, can achieve large actuation by the combined loadings of voltage-induced Maxwell stress and fluidic pressures (pneumatic and hydraulic pressure). This paper proposes a pneumatic–hydraulic coupled electromechanical actuator (PHCEA), which exhibits strong coupling effect of electromechanical actuation (the Maxwell stress on DE membrane), pneumatic and hydraulic pressures. Considering the moving boundary and state transition, a computational model has been developed to investigate the coupling behaviors of the PHCEA. The numerical result by this model is in accordance with the experimental measurements. The combination of experimental data and the theoretical result indicates that the state transition and moving boundary separate the potential region of electrical breakdown and mechanical damage. This model can be utilized as a practical method to characterize the performance and guide the design of soft devices. The experimental setup and computational method of the PHCEA bring new insights into the fabrication and characterization of soft robots, adaptive optics, and flexible bio-medical devices. The PHCEA possesses wide applications in underwater robots, soft muscles, and microfluidics systems. It can serve as the gas bladder of soft swimming robots, the soft actuator of hydraulic–pneumatic coupling systems, and the gas–liquid valve of flexible microfluidics systems.
Influence of Piezoelectric Energy Transfer on the Interwell Oscillations of Multistable Vibration Energy Harvesters
Authors: Kumar Aravind , Ali Shaikh Faruque , Arockiarajan A.
Published: December 2018

This manuscript investigates the effect of nonconservative electromechanical energy transfer on the onset of interwell motions in multistable piezoelectric energy harvesters. Multistable piezoelectric energy harvesters have been proven to outperform their linear counterparts when they undergo interwell oscillations. The conditions for interwell oscillations in such harvesters are generally characterized in terms of their potential energy function. This is accurate for a stand-alone mechanical oscillator but when the piezoelectric patches and a load resistance are included, a part of the kinetic energy supplied to the system is converted into electrical energy. In this manuscript, the Melnikov necessary conditions for interwell oscillations are derived, considering the effect of this nonconservative piezoelectric energy transfer. Through Melnikov theoretic analysis, it is shown that in a tristable harvester with all the three potential wells having the same depth, a higher excitation level is required to enable exits from the middle well to the outer wells when compared to the exits from the outer wells to the middle well. This is in stark contrast to a stand-alone tristable mechanical oscillator wherein interwell motions are simultaneously enabled for all the wells having the same depth.
Topology Optimization of Dynamic Systems Under Uncertain Loads: An H∞-Norm-Based Approach
Authors: Venini Paolo
Published: December 2018

An innovative approach to topology optimization of dynamic system is introduced that is based on the system transfer-function H∞-norm. As for the structure, the proposed strategy allows to determine the optimal material distribution that ensures the minimization of a suitable goal function, such as (an original definition of) the dynamic compliance. Load uncertainty is accounted for by means of a nonprobabilistic convex-set approach (Ben-Haim and Elishakoff, 1990, Convex Models of Uncertainty in Applied Mechanics, Elsevier Science, Amsterdam). At each iteration, the worst load is determined as the one that maximizes the current dynamic compliance so that the proposed strategy fits the so-called worst case scenario (WCS) approach. The overall approach consists of the repeated solution of the two steps (minimization of the dynamic compliance with respect to structural parameters and maximization of the dynamic compliance with respect to the acting load) until convergence is achieved. Results from representative numerical studies are eventually presented along with extensions to the proposed approach that are currently under development.
Estimation of Ammonia Storage Nonuniformity for Urea-Based Selective Catalytic Reduction Systems
Authors: Lin Qinghua , Chen Pingen
Published: December 2018

Ammonia storage nonuniformity has a significant impact on the emission reduction performance of urea-based selective catalytic reduction (SCR) systems. In this paper, a unique SCR platform with two catalysts in a parallel configuration was created for investigating the impact of ammonia storage nonuniformity on the emission reduction performance in a simulation environment. The established two-cell SCR platform allows users to independently control the ammonia-to-NOx ratio (ANR) for each catalyst using two independent urea solution injectors. Simulation results over US06 cycle demonstrate that, compared to the case without ammonia storage nonuniformity, the tailpipe NOx and ammonia emissions can be increased by 6.73% and 22.0%, respectively, due to the nonuniform ammonia storage in the case of an ANR nonuniformity index (NUI) at 0.2. Furthermore, an innovative model-based method was proposed for estimating the ammonia coverage ratio nonuniformity (i.e., ammonia storage nonuniformity if storage capacity is known) by utilizing a control-oriented SCR model and the tailpipe NOx and ammonia measurements at the confluence point. Simulation results proved the effectiveness of the proposed method in estimating the ammonia coverage ratio nonuniformity.
Further Insights Into the Damping-Induced Self-Recovery Phenomenon
Authors: Kotwal Tejas , Gerard Roshail , Banavar Ravi
Published: December 2018

In a series of papers, Chang et al. proved and experimentally demonstrated a phenomenon in underactuated mechanical systems, that they termed “damping-induced self-recovery.” This paper further investigates a few features observed in these demonstrated experiments and provides additional theoretical interpretation for the same. In particular, we present a model for the infinite-dimensional fluid–stool–wheel system, that approximates its dynamics to that of the better understood finite dimensional case, and comment on the effect of the intervening fluid on the large amplitude oscillations observed in the bicycle wheel–stool experiment.
Experimental Study on the Effect of Low Acute Side Angles on Heat Transfer in Rhombic Shaped Microchannel
Authors: Dwivedi Sunil K. , Saha Sandip K.
Published: December 2018

This experimental study on rhombic shaped microchannels was conducted to understand the effect of a low acute side angle on the Nusselt number and compare the results with the published numerical results for H1 (axially constant heat flux and circumferentially constant temperature) and H2 (constant axial and circumferential wall heat flux) boundary conditions. The hydraulic and heat transfer characteristics of the rhombic geometry with a side angle of 30 deg for different mass flow rates and heat flux inputs are obtained using a three-dimensional (3D) conjugate heat transfer model, which is validated with the experimental results. It is found that the average Nusselt number obtained from the experimental and numerical results can be approximated closely with that computed using the H1 boundary condition. The local Nusselt number of hydrodynamically and thermally developed regions obtained from the numerical analysis is compared with a correlation for the H1 boundary condition. These results will be useful in design and optimization of a rhombic shaped microchannel for electronic cooling applications.
Experimental Study of a Single Microchannel Flow Under Nonuniform Heat Flux
Authors: Eltaweel Ahmed , Hassan Ibrahim
Published: December 2018

Nonuniform heat fluxes are commonly observed in thermo-electronic devices that require distinct thermal management strategies for effective heat dissipation and robust performance. The limited research available on nonuniform heat fluxes focus mostly on microchannel heat sinks while the fundamental component, i.e., a single microchannel, has received restricted attention. In this work, an experimental setup for the analysis of variable axial heat flux is used to study the heat transfer in a single microchannel with fully developed flow under the effect of different heat flux profiles. Initially, a hot spot at different locations, with a uniform background heat flux, is studied at different Reynolds numbers, while varying the maximum heat fluxes in order to compute the heat transfer in relation to its dependent variables. Measurements of temperature, pressure, and flow rates at a different locations and magnitudes of hot spot heat fluxes are presented, followed by a detailed analysis of heat transfer characteristics of a single microchannel under nonuniform heating. Results showed that upstream hotspots have lower tube temperatures compared to downstream ones with equal amounts of heat fluxes. This finding can be of importance in enhancing microchannel heat sinks effectiveness in reducing maximum wall temperatures for the same amount of heat released, by redistributing spatially fluxes in a descending profile.
Does the Preferences for Creativity Scale Predict Engineering Students' Ability to Generate and Select Creative Design Alternatives?
Authors: Toh Christine , Miller Scarlett R.
Published: December 2018

Creativity is universally acknowledged as an important attribute of successful engineering design, but individual attributes and preferences can influence whether creative ideas come to fruition during the design process. However, few studies have explored the factors that can predict creative concept generation and selection in engineering design education. Thus, the current study was developed to provide an empirical understanding of how student designers' preferences for creativity predicts their ability to generate or select creative design alternatives during the concept screening process above and beyond the effects of personality through an empirical study with 178 engineering students. The factors explored included the Big 5 factors of personality, the preferences for creativity scale (PCS), and the novelty and quality of ideas generated and screened. The results show that the openness personality trait can predict the novelty of generated ideas as well as the novelty and quality of selected ideas during the concept screening process and that the creative confidence and preference factor of the PCS can predict the novelty of generated ideas and the novelty and quality of selected ideas during the concept screening process beyond the Big 5 factors of personality. A similar finding was obtained for the risk tolerance factor of the PCS. These findings demonstrate the importance of an individual's attitude toward risk and their creative confidence in the generation and selection of ideas in engineering education and provide a foundation for future research geared at building student innovation capacities.
Experimental Investigation of Impinging Heat Transfer of the Pulsed Chevron Jet on a Semicylindrical Concave Plate
Authors: Lyu Yuan-wei , Zhang Jing-zhou , Liu Xi-cheng , Shan Yong
Published: December 2018

Impinging heat transferred by a pulsed jet induced by a six-chevron nozzle on a semicylindrical concave surface is investigated by varying jet Reynolds numbers (5000 ≤ Re ≤ 20,000), operational frequencies (0 Hz ≤ f ≤ 25 Hz), and dimensionless nozzle-to-surface distances (1 ≤ H/d ≤ 8) while fixing the duty cycle as DC = 0.5. The semicylindrical concave surface has a cylinder diameter-to-nozzle diameter ratio (D/d) of 10. The results show that the nozzle-to-surface distance has a significant impact on the impingement heat transfer of the pulsed chevron jet. An optimal nozzle-to-surface distance for achieving the maximum stagnation Nusselt number appears at H/d  =  6. In the wall jet zone, the averaged Nusselt number is the largest at H/d = 2 and the smallest at H/d = 8. In comparison with the chevron steady jet impingement, the effect of nozzle-to-surface distance on the convective heat transfer becomes less notable for the pulsed chevron jet impingement. The stagnation Nusselt number under the pulsed chevron jet impingement is mostly less than that under the chevron steady jet impingement. However, at H/d = 8, the pulsed chevron jet is more effective than the steady jet. This study confirmed that the pulsed chevron jet produced higher azimuthally averaged Nusselt numbers than the steady chevron jet in the wall jet flow zone at large nozzle-to-surface distances. The stagnation Nusselt numbers by the pulsed chevron jet impingement have a maximum reduction of 21.0% (f = 20 Hz, H/d = 4, and Re = 2000) compared with that of the steady chevron jet impingement. Also, the pulsed chevron jet impingement heat transfer on a concave surface is less effective compared to a flat surface. The stagnation Nusselt numbers on the semicylindrical concave surface have a maximum reduction of about 37.7% (f = 20 Hz, H/d = 8, and Re = 5000) compared with that on the flat surface.
Nonlinear rheology of polydisperse blends of entangled linear polymers: Rolie-Double-Poly models
Authors: Boudara Victor A. H. , Peterson Joseph D. , Leal L. Gary , Read Daniel J.
Published: December 2018

While there has been much success in modeling the linear and nonlinear rheology of monodisperse entangled linear polymers, progress in the constitutive modeling of polymeric materials continues to lag behind the needs of industry. Industrially sourced polymers are typically polydisperse (comprising a broad distribution of molecular weights), making their rheology more suitable for processing but also more difficult to predict. To date, there are no molecular-based constitutive models that are practically suitable for describing industrially relevant polymers in industrially relevant flows. In this article, we extend but strongly simplify the model of Read et al. [J. Rheol. 56, 823–873 (2012)], which is able to predict the linear and nonlinear rheology of bidisperse blends but is prohibitively complex for industrial use. We propose a pair of simplified tube models for polydisperse melts of entangled linear polymers that combine the success of the double reptation approximation [des Cloizeaux, Europhys. Lett. 5, 437–442 (1988)] in the linear regime with the success of the Rolie-Poly constitutive equation [Likhtman et al., J. Non Newtonian Fluid Mech. 114, 1–12 (2003)] in the nonlinear regime. We first review the key concepts of the double reptation approximation and the original (monodisperse) Rolie-Poly constitutive model. Subsequently, we provide the details of our approximate models for the particular case of a bidisperse blend and show that these models naturally identify the effects from couplings between constraint release and chain retraction (i.e., the so-called “enhanced stretch relaxation time”). Finally, we generalize to a multicomponent (polydisperse) model, based on the same underlying principles. Along the way, we also show that both of our models are in qualitative, and largely quantitative, agreement with experimental data for bidisperse and polydisperse melts of entangled linear polymers.
Reading, Watching, and Tweeting About Sports: An Analysis of Sport-News Retention
Authors: Moore Joseph H.
Published: December 2018

Much research has been conducted relating to uses-and-gratification theory and how audiences select their news medium and message. Research has examined how newspapers, television stations, and social media outlets such at Twitter present news. However, no research has examined from which medium the audience retains the most information. Through the lens of uses-and-gratification theory, this exploratory study used a 4 × 1 experimental design to fill this gap. A convenience sample of 285 students at a large Midwestern university was invited to participate. A total of 122 responded to the invitation (N = 122). While most reported getting the majority of their sports news via television, participants who were presented news in print scored significantly higher on a retention test than did their counterparts who consumed news via television or Twitter. Avid sports fans retained more information, and the presence of links and images in Twitter did have an impact on how much news was retained. Implications for further research are also discussed.
Reliability and Validity of Commercially Available Low-Cost Bioelectrical Impedance Analysis
Authors: Vasold Kerri L. , Parks Andrew C. , Phelan Deanna M.L. , Pontifex Matthew B. , Pivarnik James M.
Published: December 2018

Research comparing portable body composition methods, such as bioelectrical impedance analysis (BIA), to air displacement plethysmography (ADP) is limited. We assessed reliability and validity of predicting fat-free mass (FFM) by the RJL, Omron, and Tanita BIA machines using ADP via BodPod as a criterion. FFM (kg) was assessed twice in college students (N = 77, 31 males and 46 females; age = 19.1 ± 1.2 years) using ADP, RJL, Omron, and Tanita BIAs. Reliability was assessed using analysis of variance to obtain an intraclass correlation statistic (Rxx). Validity was assessed using Pearson correlation (r) coefficient. FFM averaged 75.6 ± 9.4 kg in men and 59.8 ± 7.6 kg in women. Reliability was high in both genders RJL (Rxx = .974–.994), Omron (Rxx = .933–.993), and Tanita (Rxx = .921–.991). Validity within males was also high: RJL (r = .935), Omron (r = .942), and Tanita (r = .934), and only slightly lower in females: RJL (r = .924), Omron (r = .897), and Tanita (r = .898). The RJL, Omron, and Tanita BIA machines appear to be both reliable and valid for predicting FFM of male and female college students. Therefore, any of these three BIA devices is appropriate to use for body composition assessment in a healthy adult population.