bluuebunny/crossref_metadata_2025 huggingface dataset:
Trends of Cholecystectomies for Presumed Biliary Dyskinesia in Children in the United States
Authors: Matta Sravan R. , Kovacic Katja , Yan Ke , Simpson Pippa , Sood Manu R.
Published: October 2017

Background:

Biliary dyskinesia (BD) is a controversial clinical entity. Standardized diagnostic test and management guidelines are lacking in children. Published data suggest that long‐term outcomes of surgical and medical management are similar. We sought to determine national population‐based trends of cholecystectomies performed in children for BD and associated healthcare expenditure in the United States during a 10‐year period.

Methods:

Using Nationwide Inpatient Sample and the International Classification of Diseases, the 9th revision clinical modification codes, we identified children who had a cholecystectomy for BD from 2002 to 2011 in the United States.

Results:

A total of 66,380 cholecystectomies were identified as primary procedural diagnosis using weighted analysis from 2002 to 2011 in children. BD was the primary indication for cholecystectomy in 6674 (10.8%) of the patients. During the study period, the number of cholecystectomies performed for BD in children increased from 6.6% in 2002 to 10.6% in 2011, and a majority were adolescent white females. The annual health care expenditure for surgical management of BD for children in the US was estimated to almost $16 million/year.

Conclusions:

Despite lack of standardized diagnostic criteria and variable outcomes of surgical intervention reported in pediatric literature, cholecystectomies are commonly performed for children with BD in the United States. Consensus guidelines for the diagnosis and management of this controversial disorder in children are needed.
The Italian version of the Outpatient Physical Therapy Improvement in Movement Assessment Log: cross-cultural adaptation and psychometric properties
Authors: Vanti Carla , Villafañe Jorge H. , Branchini Mirco , Giacobazzi Mauro , Ruggeri Martina , Negrini Stefano , Guccione Andrew , Pillastrini Paolo
Published: October 2017

Instruments to measure movement abilities from a patient’s perspective are generally unavailable across diverse cultures and languages. The aim of this study was to translate, culturally adapt, and validate the Italian version of the Outpatient Physical Therapy Improvement in Movement Assessment Log (OPTIMAL) confidence scale. This study was an observational multicenter study. The Italian version of the OPTIMAL confidence scale (OPTIMAL-I) was developed following forward–backward translation and pretesting with a small group of patients. Reliability was measured by internal consistency (Cronbach α), and a factor analysis was carried out to explore the internal structure. Convergent validity was measured by comparing the OPTIMAL-I with the Italian version of the Activities-specific Balance Confidence (ABC-I). The process for obtaining the OPTIMAL-I required 3 months and it was administered to 290 outpatients in two different rehabilitation clinics. OPTIMAL-I showed high acceptability, high internal consistency (Cronbach’s α=0.963), and high test–retest stability (intraclass correlation coefficient=0.92, P=0.001). Convergent validity with ABC-I was also high (r=0.56–0.86; P<0.001). Using factor analysis, we found evidence for a four-factor structure related to ‘confidence with high-loads lower-extremity mobility’, ‘confidence with low-loads lower-extremity mobility’, ‘confidence with upper-extremity mobility’, and ‘confidence with trunk mobility’ that explained 78.83% of the total variance. The OPTIMAL-I showed good psychometric properties and its use can be recommended for measuring confidence in Italian patients receiving physical therapy services. Future studies should focus on divergent validity and construct validity.
New Evidence to Guide Ectopic Pregnancy Diagnosis and Management
Authors: Brady Paula C.
Published: October 2017

Importance

Ectopic pregnancy is a leading source of morbidity and mortality in pregnancy, accounting for 1% to 2% of all pregnancies. Timely diagnosis and management of these abnormal gestations are vital to patient safety.

Objective

The objective of this study was to describe recent evidence in the risk factors, diagnosis, and management of ectopic pregnancy.

Evidence Acquisition

Comprehensive review of the published literature.

Results

Recent literature describes newly identified risk factors for ectopic pregnancy, particularly those specific to assisted reproduction. Furthermore, evidence mounts for the utility of endometrial sampling for the diagnosis of pregnancy location, allowing a significant proportion of women to avoid methotrexate by diagnosing failing intrauterine pregnancies instead. Finally, recent, high-level evidence supports (in women with normal contralateral fallopian tubes) the equivalence of salpingectomy and salpingostomy regarding rates of subsequent intrauterine pregnancy and recurrent ectopic pregnancy.

Conclusions and Relevance

While serial serum human chorionic gonadotropin levels and transvaginal ultrasound are the mainstays of ectopic pregnancy diagnosis, recent publications revisit the utility of endometrial sampling in diagnosing pregnancy location, using manual vacuum aspiration instead of the criterion-standard dilation and curettage. Expectant management of ectopic pregnancies is the subject of ongoing research, and in the meantime, treatment remains medical or surgical (dependent on clinical parameters and patient preference); salpingostomy and salpingectomy provide equivalent subsequent pregnancy outcomes in women with contralateral fallopian tubes in place.

Target Audience

Obstetricians and gynecologists, family physicians.

Learning Objectives

After completing this activity, the learner should be better able to describe risk factors for ectopic pregnancies, including specifics of assisted reproduction; discuss updated diagnosis algorithms for pregnancies of unknown location, including recent data regarding endometrial sampling; and discuss top-level evidence regarding management of ectopic pregnancy, including expectant management, medical treatment with various methotrexate regimens, and surgical management with salpingectomy versus salpingostomy.
Association of Gestational Weight Gain With Maternal and Infant Outcomes: A Systematic Review and Meta-analysis
Authors: Goldstein Rebecca F. , Abell Sally K. , Ranasinha Sanjeeva , Misso Marie , Boyle Jacqueline A. , Black Mary Helen , Li Nan , Hu Gang , Corrado Francesco , Rode Line , Kim Young Ju , Haugen Margaretha , Song Won O. , Kim Min Hyoung , Bogaerts Annick , Devlieger Roland , Chung Judith H. , Teede Helena J.
Published: October 2017

(Abstracted from JAMA 2017;317(21):2207–2225)

Gestational weight gain (GWG) in excess of Institute of Medicine (IOM) guidelines has been associated with adverse pregnancy outcomes including preeclampsia, postpartum weight retention, and offspring obesity. Prevalence of obesity and excess GWG are becoming more prevalent from 40% in 2013 to 2014, with more than 50% of obese pregnant women gaining gestational weight greater than IOM GWG recommendations in a US study from 2002 to 2008.
Job Burnout Reduces Hand Hygiene Compliance Among Nursing Staff
Authors: Manomenidis Georgios , Panagopoulou Efharis , Montgomery Anthony
Published: October 2017

Objectives

Health professional burnout has been associated with suboptimal care and reduced patient safety. However, the extent to which burnout influences hand hygiene compliance among health professionals has yet to be explored. The aim of the study was to examine whether job burnout reduces hand washing compliance among nursing staff.

Methods

A diary study was conducted. Forty registered nurses working in a general city hospital in Thessaloniki, Greece, completed a questionnaire, while they were monitored for hand hygiene compliance following the World Health Organization protocol for hand hygiene assessment. Burnout was measured using validated items from the Maslach Burnout Inventory. Data were collected from September to October 2015.

Results

Multiple regression analysis showed that controlling for years in practice, burnout was negatively associated with hand hygiene compliance (R
2 = 0.322, F(3,36) = 5.704, P < 0.01). Nurses reporting higher levels of burnout were less likely to comply with hand hygiene opportunities (b = − 3.72, 95% confidence interval = −5.94 to −1.51).

Conclusions

This study showed that burnout contributes to suboptimal care by reducing compliance to hand hygiene among nurses. Given the crucial role of hand hygiene compliance for the prevention of in-hospital infections, this study highlights the need for interventions targeting the prevention of burnout among nursing staff.
Sequence, Structure and Context Preferences of Human RNA Binding Proteins
Authors: Dominguez Daniel , Freese Peter , Alexis Maria , Su Amanda , Hochman Myles , Palden Tsultrim , Bazile Cassandra , Lambert Nicole J , Van Nostrand Eric L , Pratt Gabriel A. , Yeo Gene W. , Graveley Brenton R. , Burge Christopher B.
Published: October 2017

Production of functional cellular RNAs involves multiple processing and regulatory steps principally mediated by RNA binding proteins (RBPs). Here we present the affinity landscapes of 78 human RBPs using an unbiased assay that determines the sequence, structure, and context preferences of an RBPin vitrofrom deep sequencing of bound RNAs. Analyses of these data revealed several interesting patterns, including unexpectedly low diversity of RNA motifs, implying frequent convergent evolution of binding specificity toward a relatively small set of RNA motifs, many with low compositional complexity. Offsetting this trend, we observed extensive preferences for contextual features outside of core RNA motifs, including spaced “bipartite” motifs, biased flanking nucleotide context, and bias away from or towards RNA structure. These contextual features are likely to enable targeting of distinct subsets of transcripts by different RBPs that recognize the same core motif. Our results enable construction of “RNA maps” of RBP activity without requiring crosslinking-based assays, and provide unprecedented depth of information on the interaction of RBPs with RNA.
Dental restoration longevity among geriatric and adult special needs patients
Authors: Caplan D. J. , Li Y. , Wang W. , Kang S. , Marchini L. , Cowen H. J. , Yan J.
Published: October 2017

This study aimed to describe the survival trajectory of dental restorations placed in an outpatient population of geriatric and adult special needs patients over a 15-year span, with particular interest in longevity of subsequent restorations in teeth that received multiple restorations over time. Dental restorations of different types and sizes in patients age ≥65 years treated between 2000-14 at the University of Iowa, College of Dentistry were followed until they incurred an event (i.e., restoration replacement, extraction of the tooth, or endodontic treatment of the tooth). Survival analysis and extended Cox regression models were used to generate hazards ratios for selected predictor variables. A total of 9184 restorations were followed in 1551 unique patients. During the follow-up period, 28.7% of these restorations incurred an event; and overall the restorations had a median lifespan of 6.25 years. In multivariable regression models, after controlling for gender and age, composite restorations and greater number of restoration surfaces were associated with higher risks of failure; and the initial restoration recorded in the database for each subject tended to have lower risk of failure than restorations placed later that included any of those same surfaces. This information potentially could be helpful to elderly patients considering various restorative treatment options during the dental treatment planning and informed consent process.
Identifying accurate metagenome and amplicon software via a meta-analysis of sequence to taxonomy benchmarking studies
Authors: Gardner Paul P. , Watson Renee J. , Morgan Xochitl C. , Draper Jenny L. , Finn Robert D. , Morales Sergio E. , Stott Matthew B.
Published: October 2017

Environmental DNA sequencing has rapidly become a widely-used technique for investigating a range of questions, particularly related to health and environmental monitoring. There has also been a proliferation of bioinformatic tools for analysing metagenomic and amplicon datasets, which makes selecting adequate tools a significant challenge. A number of benchmark studies have been undertaken; however, these can present conflicting results. We have applied a robust Z-score ranking procedure and a network meta-analysis method to identify software tools that are generally accurate for mapping DNA sequences to taxonomic hierarchies. Based upon these results we have identified some tools and computational strategies that produce robust predictions.
Theta phase coordinated memory reactivation reoccurs in a slow-oscillatory rhythm during NREM sleep
Authors: Schreiner Thomas , Doeller Christian F. , Jensen Ole , Rasch Björn , Staudigl Tobias
Published: October 2017

It has been proposed that sleep’s contribution to memory consolidation is to reactivate prior encoded information. To elucidate the neural mechanisms carrying reactivation-related mnemonic information, we investigated whether content-specific memory signatures associated with memory reactivation during wakefulness reoccur during subsequent sleep. We show that theta oscillations orchestrate the reactivation of memories, irrespective of the physiological state. Reactivation patterns during sleep autonomously re-emerged at a rate of 1 Hz, indicating a coordination by slow oscillatory activity.
Alpha Oscillations Prior to Encoding Preferentially Modulate Memory Consolidation during Wake Relative to Sleep
Authors: Cross Zachariah R. , Santamaria Amanda , Corcoran Andrew W. , Alday Phillip M. , Coussens Scott , Kohler Mark J.
Published: October 2017

Sleep promotes memory consolidation through unique neuromodulatory activity. However, little is known about the impact of attention during pre-sleep memory encoding on later memory performance. The current study aimed to address the question of whether attentional state prior to encoding, as indexed by alpha oscillatory activity, modulates the consolidation of images across periods of sleep and wake. 22 participants aged 18 – 41 years (mean age = 27.3) viewed 120 emotionally valenced images (positive, negative, neutral) before a 2hr afternoon sleep opportunity and an equivalent period of wake. Following the sleep and wake conditions, participants were required to distinguish between 120 previously seen (target) images and 120 new (distractor) images. Relative alpha power – adjusted according to participants’ individual alpha frequency – was computed to index attentional state prior to the learning phase. Generalised linear mixed-effects modelling revealed memory performance was modulated by attention, such that greater pre-encoding alpha power preferentially promoted memory consolidation during wake compared to sleep. There was no difference in memory performance between positive, negative and neutral stimuli. Modulations in alpha oscillatory activity may help to coordinate the flow of information between task-relevant cortical regions and a thalamo-cortical loop that preferentially subserves the formation of memory during times of wake relative to sleep.
Revising transcriptome assemblies with phylogenetic information in Agalma1.0
Authors: Guang August , Howison Mark , Zapata Felipe , Lawrence Charles , Dunn Casey
Published: October 2017

Motivation

One of the most common transcriptome assembly errors is to mistake different transcripts of the same gene as transcripts from multiple closely related genes. It is difficult to identify these errors during assembly, but in a phylogenetic analysis these errors can be diagnosed from gene trees containing clades of tips from the same species with improbably short branch lengths.

Results

treeinform is a module implemented in Agalma1.0 that uses phylogenetic analyses across species to refine transcriptome assemblies. It identifies transcripts of the same gene that were incorrectly assigned to multiple genes and reassign them as transcripts of the same gene.

Availability and Implementation

treeinform is implemented in Agalma1.0, available at https://bitbucket.org/caseywdunn/agalma.

Contact

august_guang@brown.edu

Supplementary information

Supplementary information is available at bioRxiv.
Characterization of a sCMOS-based high-resolution imaging system
Authors: Mittone Alberto , Manakov Ilja , Broche Ludovic , Jarnias Christophe , Coan Paola , Bravin Alberto
Published: October 2017

The detection system is a key part of any imaging station. Here the performance of the novel sCMOS-based detection system installed at the ID17 biomedical beamline of the European Synchrotron Radiation Facility and dedicated to high-resolution computed-tomography imaging is analysed. The system consists of an X-ray–visible-light converter, a visible-light optics and a PCO.Edge5.5 sCMOS detector. Measurements of the optical characteristics, the linearity of the system, the detection lag, the modulation transfer function, the normalized power spectrum, the detective quantum efficiency and the photon transfer curve are presented and discussed. The study was carried out at two different X-ray energies (35 and 50 keV) using both 2× and 1× optical magnification systems. The final pixel size resulted in 3.1 and 6.2 µm, respectively. The measured characteristic parameters of the PCO.Edge5.5 are in good agreement with the manufacturer specifications. Fast imaging can be achieved using this detection system, but at the price of unavoidable losses in terms of image quality. The way in which the X-ray beam inhomogeneity limited some of the performances of the system is also discussed.
Characterization of temporal coherence of hard X-ray free-electron laser pulses with single-shot interferograms
Authors: Osaka Taito , Hirano Takashi , Morioka Yuki , Sano Yasuhisa , Inubushi Yuichi , Togashi Tadashi , Inoue Ichiro , Tono Kensuke , Robert Aymeric , Yamauchi Kazuto , Hastings Jerome B. , Yabashi Makina
Published: October 2017

Temporal coherence is one of the most fundamental characteristics of light, connecting to spectral information through the Fourier transform relationship between time and frequency. Interferometers with a variable path-length difference (PLD) between the two branches have widely been employed to characterize temporal coherence properties for broad spectral regimes. Hard X-ray interferometers reported previously, however, have strict limitations in their operational photon energies, due to the specific optical layouts utilized to satisfy the stringent requirement for extreme stability of the PLD at sub-ångström scales. The work presented here characterizes the temporal coherence of hard X-ray free-electron laser (XFEL) pulses by capturing single-shot interferograms. Since the stability requirement is drastically relieved with this approach, it was possible to build a versatile hard X-ray interferometer composed of six separate optical elements to cover a wide photon energy range from 6.5 to 11.5 keV while providing a large variable delay time of up to 47 ps at 10 keV. A high visibility of up to 0.55 was observed at a photon energy of 10 keV. The visibility measurement as a function of time delay reveals a mean coherence time of 5.9 ± 0.7 fs, which agrees with that expected from the single-shot spectral information. This is the first result of characterizing the temporal coherence of XFEL pulses in the hard X-ray regime and is an important milestone towards ultra-high energy resolutions at micro-electronvolt levels in time-domain X-ray spectroscopy, which will open up new opportunities for revealing dynamic properties in diverse systems on timescales from femtoseconds to nanoseconds, associated with fluctuations from ångström to nanometre spatial scales.
Novel modification of anhydrous transition metal oxalates from powder diffraction
Authors: Puzan Anna N. , Baumer Vyacheslav N. , Mateychenko Pavel V.
Published: October 2017

The known metal–C2O4 structures may be divided into two modifications, α and β. The α-modification has an order–disorder struxture, revealing one-dimensional disordering of the metal–oxalate chains, and the β-modification is ordered. The crystal structures of orthorhombic γ-MnC2O4 {poly[μ-oxalato-manganese(II)]; space group Pmna, a = 7.1333 (1), b = 5.8787 (1), c = 9.0186 (2) Å, V = 378.19 (1) Å3, Z = 4 and Dx
= 2.511 Mg m−3} and γ-CdC2O4 {poly[μ-oxalato-cadmium(II)]; space group Pmna, a = 7.3218 (1), b = 6.0231 (1), c = 9.2546 (2) Å, V = 408.13 (1) Å3, Z = 4 and Dx
= 3.262 Mg m−3} have been obtained from powder diffraction patterns. The structures are isostructural. Each metal atom in each structure is coordinated by seven O atoms which belong to five oxalate ions. The crystal packing, which contains noticeable cavities in the [101] and [001] directions, is not close packed and essentially differs from the known disordered α- and ordered β-modifications of transition metal oxalates. This modification seems to be metastable. It was found that a spontaneous γ→β phase transition takes place for γ-CdC2O4.
MGM(1,m) model based on interval grey number sequence and its applications
Authors: Xiong Pingping , Zhang Yue , Zeng Bo , Yao Tian-Xiang
Published: October 2017

Purpose

Aiming at the traditional multivariate grey forecasting model only considers the modelling of real numbers; therefore, the purpose of this paper is to construct an MGM(1, m) model based on the interval grey number sequences according to the grey modelling theory.

Design/methodology/approach

First, the multivariable grey number sequences are transformed into the kernel and grey radius sequences which are two feature sequences of interval grey number sequences. Then the MGM(1, m) model for kernel sequences and grey radius sequences are established, respectively. Finally, the simulation and prediction of the upper and lower bounds of the interval grey number sequences are realized by the reductive calculation of the predicted values of the kernel and grey radius.

Findings

The model is applied to the prediction of visibility and relative humidity, the identification factors of the haze. The results show that the model has high accuracy on the simulation and prediction of multivariable grey number sequences, which is reasonable and practical.

Originality/value

The main contribution of this paper is to propose a method to simulate and forecast the multivariable grey number sequence that is to establish the prediction models for the whitening sequences of multivariable grey number sequences which are kernel and grey radius sequences and extend the possibility boundary of kernel by grey radius. The model can reflect the development trend of multivariable grey number sequence accurately. When the grey information is continuously complemented, the multivariable grey number prediction model is transformed into the traditional MGM(1, m) model. Therefore, the MGM(1, m) model based on interval grey number sequence is the generalisation and expansion of the traditional MGM(1, m) model.
Energy-related CO2 emission forecast for Turkey and Europe and Eurasia
Authors: Ayvaz Berk , Kusakci Ali Osman , Temur Gül T.
Published: October 2017

Purpose

The global warming, caused by the anthropogenic greenhouse gases, has been one of the major worldwide issues over the last decades. Among them, carbon dioxide (CO2) is the most important one and is responsible for more than the two-third of the greenhouse effect. Currently, greenhouse gas emissions and CO2 emissions – the root cause of the global warming – in particular are being examined closely in the fields of science and they also have been put on the agenda of the political leaders. The purpose of this paper is to predict the energy-related CO2 emissions through using different discrete grey models (DGMs) in Turkey and total Europe and Eurasia region.

Design/methodology/approach

The proposed DGMs will be applied to predict CO2 emissions in Turkey and total Europe and Eurasia region from 2015 to 2030 using data set between 1965 and 2014. In the first stage of the study, DGMs without rolling mechanism (RM) will be used. In the second stage, DGMs with RM are constructed where the length of the rolling horizons of the respected models is optimised.

Findings

In the first stage, estimated values show that non-homogeneous DGM is the best method to predict Turkey’s energy-related CO2 emissions whereas DGM is the best method to predict the energy-related CO2 emissions for total Europe and Eurasia region. According to the results in the second stage, NDGM with RM (k=26) is the best method for Turkey while optimised DGM with RM (k=4) delivers most reliable estimates for total Europe and Eurasia region.

Originality/value

This study illustrates the effect of different DGM approaches on the estimation performance for the Turkish energy-related CO2 emission data.
Investigating market orientation and positioning in star-rated hotels in Ghana
Authors: Hinson Robert Ebo , Abdul-Hamid Ibn Kailan , Osabutey Ellis L.C.
Published: October 2017

Purpose

Market orientation and positioning have been widely recognized as organizational metrics linked to hotel performance. The purpose of this study is to offer the link among market orientation, positioning and hotel performance in Ghana’s (luxury) hotel sector. It also reports on the joint influence of market orientation and positioning on hotel performance in the same sector.

Design/methodology/approach

Three hypotheses were investigated on the link between market orientation and hotel performance, positioning and hotel performance, and the joint effect of market orientation and positioning on hotel performance. A survey of star-rated (luxury) hotels in the capital city of Ghana was used. One hundred and five responses were used in the analysis. Descriptive statistics, exploratory factor analysis and hierarchical regression were used to test the three hypotheses.

Findings

All hypotheses were accepted. Market orientation and positioning jointly affect hotel performance, and the study provides hotel managers with suggestions on how to enhance their performance via market orientation and positioning.

Research limitations/implications

Market orientation, positioning, and performance measures focused on management perspectives without including perceptions of customers.

Originality/value

This study is one of the few attempts to systematically investigate the intertwined concepts of market orientation, positioning and performance in a developing economy hospitality context.
Research on rheological and flow behavior of lubricating grease in extremely cold weather
Authors: Yan Fei , Wang Ziyu , Du Yuchen , Su Shijie , Zheng Yan , Li Qinfeng
Published: October 2017

Purpose

This paper aims to investigate the flow characteristics of lubricating grease in extremely cold weather in which it is difficult to convey the grease due to a huge pressure drop.

Design/methodology/approach

The rheological behavior of grease at various temperatures is studied by a rotary rheometer to determine the constitutive equation of lubricating grease. Based on the Herschel–Bulkley (H–B) model, the flow pattern of grease is then simulated by computational fluid dynamics and compared with the test results.

Findings

The yield stress increased dramatically when the shear rate was less than 1s−1 in the rheological experiments of continuous shear mode, and the phenomenon was more significant with the decrease in temperature. The rheological data obtained from the continuous shear mode agrees with the H–B equation after the shear thinned. In extremely cold conditions, there is a large yield stress in the lubricating grease; the numerical results show that the viscosity of lubricating grease increased with an increase in temperature, and the viscosity and velocity of lubricating grease showed uneven distribution leading to difficulty of lubricating grease delivery.

Originality/value

This paper focuses on the flow characteristics of lubricating grease in extremely cold area conditions which is studied rarely. In addition, the continuous shear model and oscillatory model are combined to establish the constitutive equations. Experiment and numerical simulation method are all used by establishing the H–B models.
Theoretical analysis and experimental study on thermal stability of high-speed motorized spindle
Authors: Liu Zhe , Chen Wei , Li Desheng , Zhang Wenjing
Published: October 2017

Purpose

In high-speed processing, the influence on the machining accuracy of a machine tool is greatly caused by the thermal deformation of the motorized spindle; a further study on the thermal characteristics of the spindle is given in this paper. This study aims to reduce the thermal error and improve the performance of the machine tool by discussing the relationships between the temperature distributions and rotating accuracy caused by the thermal deformations of the spindle.

Design/methodology/approach

The paper opted for a method combining the theoretical analysis and the experimental study to study the thermal stability of the high-speed motorized spindle. First of all, a finite element model of the spindle was built with ANSYS, whereby temperature distributions and the thermal deformations were successively obtained at different speeds. And then, both the temperature field and the rotating accuracy of the motorized spindle were measured simultaneously by the thermal stability experiment. Finally, the experimental and theoretical results were compared and validated.

Findings

The thermal stability of the motorized spindle was studied in this paper, and some findings from the study were as follows: the spindle’s rotating accuracy maintained good in X direction but bad in Y and Z directions in terms of the deformations; the higher front-end temperature of the spindle which can significantly affect the rotating accuracy is needed to be controlled mainly; the recovery speed of the spindle deformation lagged behind the temperature’s fallback speed; the vibration graph about radial rotating sensitivity synthesized by X1 and X2 presented a trifoliate shape.

Originality/value

Based on a built test-bed which can synchronously measure the motorized spindle’s temperature distribution and rotating accuracy with five-point method, the coupling effects of the thermal deformation and temperature are embodied, and not only the vibration graph but also the thermal tilt angles can be gained. Therefore, considering the influence of the thermal deformation on the heat generated by the bearings, the paper fulfilled a study by which it was obtained that the front-end temperature of the spindle, which was higher and could significantly affect the rotating accuracy, needed to be controlled mainly.
Effect of surface roughness and deformation on Rayleigh step bearing under thin film lubrication
Authors: Kumar Rahul , Azam Mohammad Sikandar , Ghosh Subrata Kumar , Khan Hasim
Published: October 2017

Purpose

The aim of this paper is to study the effect of deterministic roughness and small elastic deformation of surface on flow rates, load capacity and coefficient of friction in Rayleigh step bearing under thin film lubrication.

Design/methodology/approach

Reynolds equation, pressure-density relationship, pressure-viscosity relationship and film thickness equation are discretized using finite difference method. Progressive mesh densification (PMD) method is applied to solve the related equations iteratively.

Findings

The nature and shape of roughness play a significant role in pressure generation. It has been observed that square roughness dominates the pressure generation for all values of minimum film thickness. Deformation more than 100 nm in bounding surfaces influences the film formation and pressure distribution greatly. Divergent shapes of film thickness in step zone causes a delay of pressure growth and reduces the load capacity with decreasing film thickness. The optimum value of film thickness ratio and step ratios have been found out for the maximum load capacity and minimum coefficient of friction, which are notably influenced by elastic deformation of the surface.

Practical implications

It is expected that these findings will help in analysing the performance parameters of a Rayleigh step bearing under thin film lubrication more accurately. It will also help the designers, researchers and manufacturers of bearings.

Originality/value

Most of the previous studies have been limited to sinusoidal roughness and thick film lubrication in Rayleigh step bearing. Effect of small surface deformation due to generated pressure in thin film lubrication is significant, as it influences the performance parameters of the bearing. Different wave forms such as triangular, sawtooth, sinusoidal and square formed during finishing operations behaves differently in pressure generation. The analysis of combined effect of roughness and small surface deformation has been performed under thin film lubrication for Rayleigh step bearing using PMD as improved methods for direct iterative approach.
Surface temperature and wear particle analysis of vertical motion double-nut ball screws
Authors: Horng Jeng-Haur , Chern Shin-Yuh , Li Chi-Lin , Chen Yang-Yuan
Published: October 2017

Purpose

This paper aims to investigate the temperature and wear properties of vertical ball screws and to discuss the surface design of ball screws in industrial applications.

Design/methodology/approach

The energy equation of the screw surface considering the frictional heat was established to verify the surface temperature of the ball screw. X-ray diffraction was used to examine the micro-contact temperature between the ball and screw. Debris size and density were examined to investigate wear properties of ball screws and to study the relationship of wear debris and temperature.

Findings

First, the main energy source for the surface temperature of high speed vertical ball screws is derived from friction force between ball and screw. Second, the temperature rise between the ball and screw has great relevance with wear debris concentration. Third, the surface temperature of the screw is higher than between the nut and ball for high speed vertical ball screws due to high convection heat transfer. The contact temperature of the nut near the flange is smaller than that of the nut away from the flange end due to the high contact load and thermal conduction. Finally, correlation of particle size and surface roughness value for vertical ball screws was established, and its effects on contact temperature were studied. The theoretical analysis and experiments will help to characterize the design and manufacture of vertical ball screws.

Originality/value

The surface temperature and micro-contact temperature analytical model were established to study the ball screw design. Based on the surface-particle micro-contact temperature balance, the optimal range of surface roughness was designed for vertical ball screws, considering the wear debris and micro-contact temperature.
Wear behavior of micro-coined steel surfaces under mixed lubrication
Authors: Rosenkranz Andreas , Khan Saad Ahmed , Szurdak Adam , Hirt Gerhard , Gachot Carsten
Published: October 2017

Purpose

The purpose of this study is to investigate the influence of hemispherical structures fabricated by hot micro-coining on the resulting wear performance. Hemispherical structures with different area densities (20 and 30 per cent), depths (50 and 100 µm) and diameters (100 and 200 µm) were fabricated by hot micro-coining on stainless steel samples.

Design/methodology/approach

The wear performance of these samples was studied using a ball-on-disk tribometer in rotational sliding mode using a normal load of 30 N and a fixed sliding velocity of 2 cm/s. Two different poly-(alpha)-olefin (PAO) oils without any additive having a kinematic viscosity of 4 and 40 cSt, were used to study the influence of the oil viscosity on the wear behavior.

Findings

Concerning the polished reference, an enlarged wear volume with an increase in the cycle number and the oil viscosity was observed. In the case of the micro-coined surfaces, all samples demonstrate a pronounced reduction in the wear volume (up to a factor of 100 for PAO 40) compared to the polished reference irrespective of the oil viscosity used.

Originality/value

This study details new research work studying the wear behavior of hot micro-coined surfaces.
A comparative study of the friction and wear performance of Fe-based bulk metallic glass under different conditions
Authors: Segu Dawit Zenebe , Hwang Pyung
Published: October 2017

Purpose

This study aims to compare the friction and wear behaviors of Fe68.3C6.9Si2.5 B6.7P8.8Cr2.2Al2.1Mo2.5 bulk metallic glass (BMG) under sliding using dry, deionized water-lubricated and oil-lubricated conditions. The comparison was performed using a unidirectional ball-on-flat tribometer under different applied loads, and the results were compared to the properties of a conventional material, SUJ2. Fe-based BMG materials have recently been attracting a great deal of attention for prospective engineering applications.

Design/methodology/approach

As a part of the development of Fe-based BMGs that can be cost-effectively produced in large quantities, an Fe-based BMG Fe68.8C7.0Si3.5B5.0P9.6 Cr2.1Mo2.0Al2.0 with high glass forming ability was fabricated. In the present study, the friction and wear properties of Fe-based BMG has been comparatively evaluated under dry sliding, deionized water- and oil-lubricated conditions using a unidirectional ball-on-flat tribometer under different applied loads, and the results were compared to the properties of conventional material SUJ2.

Findings

The results show that the Fe-based BMG had better friction performance than the conventional material. Both the friction coefficient and wear mass loss increased with increasing load. The sliding wear mechanism of the BMG changed with the sliding conditions. Under dry sliding conditions, the wear scar of the Fe-based BMG was characterized by abrasive wear, plastic deformation, micro-cracks and peeling-off wear. Under water- and oil-lubricated conditions, the wear scar was mainly characterized by abrasive wear and micro-cutting.

Originality/value

In this investigation, the authors developed a new BMG alloy Fe68.8C7.0Si3.5B5.0P9.6Cr2.1Mo2.0Al2.0 to improve the friction and wear performance under dry sliding, deionized water- and oil- lubricated conditions.
Numerical study of surface dimple phenomenon by starvation in simple sliding contact
Authors: Cui Shun , Nishikawa Hiroshi , Wang Jing , Zou Qian
Published: October 2017

Purpose

This study aims to use a thermal elastohydrodynamic lubrication (EHL) algorithm incorporating an Eyring flow model to solve a steady-state contact in simple sliding motion.

Design/methodology/approach

A theoretical model was used to investigate the effect of starvation on the surface dimple phenomenon by gradually reducing the thickness of the inlet oil layer.

Findings

The increase in the starvation degree reduces the dimple depth, film thickness, the pressure peak and the temperature rise. Under the severe starvation condition, the dimple is eliminated so that the EHL contact becomes partly parched. In elliptical results, for the same starvation parameters, the oil replenishment is stronger than that in circular contact.

Originality/value

This paper fulfils an exploration to study how the oil starvation influences the surface dimple phenomenon.
A study of the effect of social shopping deals on online reviews
Authors: Lee In
Published: October 2017

Purpose

The purpose of this paper is to investigate social shopping deals and their impacts on review metrics at an online review site, Yelp and to compare the review metrics of the restaurant businesses and the health and wellness businesses to understand how social shopping deals affects them.

Design/methodology/approach

This study adopts a multiple regression model to analyse the effect of seven independent variables on the dependent variable, the growth rate of reviews which is a proxy of sales growth. This sample consisted of the review data of 134 merchants which offered social shopping deals at Groupon in 2011. The online review data of these merchants were collected in 2015 to analyse the relationship between the deals and the grow rate of the reviews.

Findings

For the restaurant businesses, there is a positive persuasive effect of Groupon customers’ review score on the growth rate of the reviews and consequently on the sale growth. For the health and wellness businesses, there are a positive persuasive effect of the regular customers’ review score on the growth rate of the reviews and a negative awareness effect of the number of Groupon reviews on the growth rate of the reviews. The review data also show that the Groupon customers of the health and wellness businesses are three times more likely to post their reviews than those of the restaurant businesses.

Research limitations/implications

First, while the author limited the study to the seven independent variables, additional variables may exist. These additional variables may also influence the number of reviews, too. Future research needs to identify such variables to build a comprehensive model. Second, future research needs to address other types of businesses, such as education and entertainment, and compare differences between them. Third, while the study focussed on the review score and the number of reviews, a more in-depth analysis of the comments using sentiment analysis and social network analysis may shed additional insights on their review activities.

Originality/value

Despite the potential significance of customers’ reviews about social shopping deals, the critical mass of empirical studies still lacks in this area. The study contributes to the literature of this field by investigating the effect of social shopping deals on the customers’ online reviews. This study provides practical guidance for the improvement of online reviews about social shopping deals.
An integrated social network mining for product-based technology analysis of Apple
Authors: Kim Juhwan , Jun Sunghae , Jang Dong-Sik , Park Sangsung
Published: October 2017

Purpose

Patent contains vast information on developed technologies because of the patent system. So, it is important to analyze patent data for understanding technologies. Most previous studies on patent analysis were focused on the technology itself. Their research results lacked the consideration of products. But the patent analysis based on products is crucial for company because a company grows by sales of competitive products. The purpose of this paper is to propose a novel methodology of patent analysis for product-based technology. This study contributes to the product development strategy of a company.

Design/methodology/approach

The primary goal for developing technology is to release a new product. So it is important to analyze the technology based on the product. In this study, the authors analyze Apple’s technologies based in iPod, iPhone, and iPad. In addition, the authors propose a new methodology to analyze product-based technology. The authors call this an integrated social network mining (ISNM). In the ISNM, the authors carry out a social network analysis (SNA) according to each product of Apple, and integrate all SNA results of iPod, iPhone, and iPad using the technological keywords.

Findings

In this case study, the authors analyze Apple’s technologies according to Apple’s innovative products, such as the iPod, iPhone, and iPad. From the ISNM results of Apple’s technology, the authors can find which technological detail is more important in overall structure of Apple’s technologies.

Practical implications

This study contributes to the management of technology including new product development, technological innovation, and research and development planning. To know the technological relationship between whole technologies based on products can be the source of intensification of technological competitiveness.

Originality/value

Most of studies on technology analysis were focused on patent technology itself. Though one of their research goals was to develop new product, they had their limits considering the products because they did not use the technology information in the technology analysis. The originality of this research is to use the product information in technology analysis using the proposed ISNM.
Use contexts of personal computing devices: determinants of use context changes
Authors: Kim Jimin , Choi Goya , Chang Younghoon , Park Myeong-Cheol
Published: October 2017

Purpose

The purpose of this paper is to investigate the use contexts of personal computing devices in multiple steps and conducts an in-depth analysis for the use context of smartphones. The determinants of use context changes of smartphones are investigated using the technology-to-performance chain model.

Design/methodology/approach

In steps 1 and 2, a diary study method and 2014-2015 Korea media panel research data provided by the Korea Information Society Development Institute are used. Correspondence analysis, χ2 independence tests, and standardized residual analyses were conducted. In step 3, this study develops and validates a framework for use context changes using a survey method and structural equation modeling.

Findings

The results show that the use context of personal computing devices is represented differently and is clearly defined depending on the device used. Furthermore, the use context of smartphones has changed significantly because of the rapid growth of smartphone users and diverse usage patterns of smartphones. The research model results show that users expand the scope and frequency of smartphone use when they experience improved performance in everyday tasks and feel that smartphone content and functions could support everyday tasks better.

Originality/value

This study presents novel early stage research and presents empirical evidence and propositions in both exploratory and confirmatory ways. The main contribution of this study is to provide guidelines and general implications for other empirical studies on the use contexts of devices or information technology services.
A methodology for enterprise systems post-implementation change management
Authors: Comuzzi Marco , Parhizkar Minou
Published: October 2017

Purpose

Enterprise systems (ESs) are hard to maintain, since they embed a large fraction of organisational data and tasks, which are often intertwined and highly interdependent. The purpose of this paper is to propose a methodology for enterprise resource planning (ERP) post-implementation change management to support business analysts during perfective maintenance.

Design/methodology/approach

The methodology draws a parallel line with engineering change management and considers the steps of mapping the dependencies among ES components, understanding the ripple effects of change, and defining metrics to quantify and assess the impact of change. The methodology is instantiated in the case of ERP systems, for which a tool has also been implemented and evaluated by ERP implementation experts.

Findings

Experts positively evaluated the proposed methodology. General design principles to instantiate the methodology in the case of systems other than ERP have been derived.

Originality/value

While existing ESs change management methodologies help to identify the need for change, the proposed methodology help to structure the change process, supporting the task of perfective maintenance in an efficient way.