bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Field‐Induced Ferroelectric Switching in Multiferroic Aurivillius Phase Thin Films at Room Temperature
Authors: Keeney Lynette , Maity Tuhin , Schmidt Michael , Amann Andreas , Deepak Nitin , Petkov Nikolay , Roy Saibal , Pemble Martyn E. , Whatmore Roger W.
Published: July 2013

Single‐phase multiferroic materials are of considerable interest for future memory and sensing applications. Thin films of Aurivillius phase Bi7Ti3Fe3O21 and Bi6Ti2.8Fe1.52Mn0.68O18 (possessing six and five perovskite units per half‐cell, respectively) have been prepared by chemical solution deposition on c‐plane sapphire. Superconducting quantum interference device magnetometry reveal Bi7Ti3Fe3O21 to be antiferromagnetic (TN = 190 K) and weakly ferromagnetic below 35 K, however, Bi6Ti2.8Fe1.52Mn0.68O18 gives a distinct room‐temperature in‐plane ferromagnetic signature (Ms = 0.74 emu/g, μ0Hc =7 mT). Microstructural analysis, coupled with the use of a statistical analysis of the data, allows us to conclude that ferromagnetism does not originate from second phase inclusions, with a confidence level of 99.5%. Piezoresponse force microscopy (PFM) demonstrates room‐temperature ferroelectricity in both films, whereas PFM observations on Bi6Ti2.8Fe1.52Mn0.68O18 show Aurivillius grains undergo ferroelectric domain polarization switching induced by an applied magnetic field. Here, we show for the first time that Bi6Ti2.8Fe1.52Mn0.68O18 thin films are both ferroelectric and ferromagnetic and, demonstrate magnetic field‐induced switching of ferroelectric polarization in individual Aurivillius phase grains at room temperature.
SWAT 1: what effects do site visits by the principal investigator have on recruitment in a multicentre randomized trial?
Authors: Smith Valerie , Clarke Mike , Devane Declan , Begley Cecily , Shorter Gillian , Maguire Lisa
Published: July 2013

The SWAT (Study Within A Trial) programme has been established to develop a series of studies that would embed research within research, so as to resolve uncertainties about the effects of different ways of designing, conducting, analyzing and interpreting evaluations of health and social care. It was described in an Education piece in the Journal of Evidence‐Based Medicine in 2012. We have now prepared the first example of the design summary for a SWAT, using the template that will be used for other SWAT. This is presented in this article.
The psychophysiological and health corollaries of child problem behaviours in caregivers of children with autism and ADHD
Authors: Lovell B. , Moss M. , Wetherell M. A.
Published: July 2013

Background

The positive relationship between problem behaviours of children with additional complex needs and psychological distress in their caregivers has been widely evidenced. Fewer studies, however, have assessed the relationship between care recipients’ problem behaviours and key physiological processes, relevant for the physical health status of their care providers. This study examined the psychological, endocrine and health corollaries of child problem behaviours in caregivers of children with autism and attention deficit hyperactivity disorder.

Methods

Caregivers (n = 18) completed self‐report measures of psychological distress, child problem behaviours and incidences of commonly occurring ailments. To capture important parameters of the basal diurnal cortisol pattern, caregivers collected saliva samples at waking, 30 min post waking, 1200 h and 2200 h on two consecutive weekdays.

Results

Data revealed a positive relationship between caregivers’ perceived levels of stress and problems with child conduct behaviours. In addition, caregivers who reported more problems with child emotional and hyperactivity behaviours displayed atypical cortisol patterns characterised by flatter diurnal cortisol slopes and reduced cortisol awakening response magnitude. Subjective reports of commonly occurring ailments were also greater in caregivers experiencing more problems with child emotional behaviours.

Conclusions

These findings have implications for interventions that aim to improve the psychophysiological well‐being of the caregiver by targeting problem behaviours of the care recipient.
Aspects of Orthodontic‐Prosthetic Rehabilitation of Dentofacial Anomalies
Authors: Ajduković Zorica , Janošević Mirjana , Filipović Gordana , Arsić Stojanka , Janošević Predrag , Petrović Nenad
Published: July 2013

Skeletal class III malocclusion is one of the most difficult dentofacial anomalies, characterized by deviation in the development of the mandible and maxilla in the sagittal plane, where the mandible is dominant in relation to the maxilla. In patients with class III malocclusion, anomalies in the dentoalveolar level and esthetic discrepancies are also frequent. The etiology of class III malocclusion is multifactorial due to the interaction of hereditary and environmental factors. Rehabilitation and treatment of malocclusion is one of the major goals of modern dentistry. This article presents the orthodontic‐prosthetic therapy and rehabilitation of a 45‐year‐old patient with an abnormal occlusal vertical dimension and a skeletal class III malocclusion. The patient came to the clinic complaining about degraded esthetics and disordered functions of the orofacial region (functions of eating, swallowing, speech) and also pain in the temporomandibular joint. After the diagnosis was made, the patient was first referred to orthodontic treatment with fixed orthodontic appliances (self‐ligating brackets system Rot 0.22). Upon completion of the orthodontic treatment, the patient was sent for further prosthetic treatment. Fixed prosthetic restorations were made in the upper and lower jaw, thus achieving a satisfactory result in terms of esthetics and function of the stomatognathic system.
The structure of the small animal consultation
Authors: Everitt S. , Pilnick A. , Waring J. , Cobb M.
Published: July 2013

Objectives

To analyse the structure of small animal consultations in order to increase understanding of the consultation processes, locate decision‐making in the wider practice context and stimulate further research.

Methods

Analysis of 48 video‐recorded consultations from first opinion small animal practices. These consultations were time and thematically coded in order to enable analysis.

Results

The mean length of the recorded consultations was 11 minutes and 45 seconds with a range of 4–28 minutes. Analysis indicates that both the clinical tasks and communication taking place in the consultation are often performed in an iterative and interactive fashion in contrast to the sequential methods frequently being taught.

Clinical Significance

This study shows that the consultation is a complex process that is often performed in an iterative and interactive fashion and that may be difficult to complete within the 10 minutes frequently allocated. This warrants further research.
Contrasting effects of landscape features on genetic structure in different geographic regions in the ornate dragon lizard, Ctenophorus ornatus
Authors: Levy Esther , Tomkins Joseph L. , LeBas Natasha R. , Kennington W. Jason
Published: July 2013

Habitat fragmentation can have profound effects on the distribution of genetic variation within and between populations. Previously, we showed that in the ornate dragon lizard, Ctenophorus ornatus, lizards residing on outcrops that are separated by cleared agricultural land are significantly more isolated and hold less genetic variation than lizards residing on neighbouring outcrops connected by undisturbed native vegetation. Here, we extend the fine‐scale study to examine the pattern of genetic variation and population structure across the species' range. Using a landscape genetics approach, we test whether land clearing for agricultural purposes has affected the population structure of the ornate dragon lizard. We found significant genetic differentiation between outcrop populations (FST = 0.12), as well as isolation by distance within each geographic region. In support of our previous study, land clearing was associated with higher genetic divergences between outcrops and lower genetic variation within outcrops, but only in the region that had been exposed to intense agriculture for the longest period of time. No other landscape features influenced population structure in any geographic region. These results show that the effects of landscape features can vary across species' ranges and suggest there may be a temporal lag in response to contemporary changes in land use. These findings therefore highlight the need for caution when assessing the impact of contemporary land use practices on genetic variation and population structure.
ICEA of Mycoplasma agalactiae: a new family of self‐transmissible integrative elements that confers conjugative properties to the recipient strain
Authors: Dordet Frisoni Emilie , Marenda Marc Serge , Sagné Eveline , Nouvel Laurent Xavier , Guérillot Romain , Glaser Philippe , Blanchard Alain , Tardy Florence , Sirand‐Pugnet Pascal , Baranowski Eric , Citti Christine
Published: July 2013

Horizontal gene transfer (HGT) is a major force of microbial evolution but was long thought to be marginal in mycoplasmas. In silico detection of exchanged regions and of loci encoding putative Integrative Conjugative Elements (ICE) in several mycoplasma genomes challenged this view, raising the prospect of these simple bacteria being able to conjugate. Using the model pathogen Mycoplasma agalactiae, we demonstrated for the first time that one of these elements, ICEA, is indeed self‐transmissible. As a hallmark of conjugative processes, ICEA transfers were DNase resistant and required viable cells. ICEA acquisition conferred ICE‐negative strains with the new ability to conjugate, allowing the spread of ICEA. Analysis of transfer‐deficient mutants indicated that this process requires an ICEA‐encoded lipoprotein of unknown function, CDS14. Formation of a circular extrachromosomal intermediate and the subsequent chromosomal integration of ICEA involved CDS22, an ICEA‐encoded product distantly related to the ISLre2 transposase family. Remarkably, ICEA has no specific or no preferential integration site, often resulting in gene disruptions. Occurrence of functional mycoplasma ICE offers these bacteria with a means for HGT, a phenomenon with far‐reaching implications given their minute‐size genome and the number of species that are pathogenic for a broad host‐range.
A mechanical signal transmitted by the flagellum controls signalling in Bacillus subtilis
Authors: Cairns Lynne S. , Marlow Victoria L. , Bissett Emma , Ostrowski Adam , Stanley‐Wall Nicola R.
Published: July 2013

In the natural environment bacteria predominantly live adhered to a surface as part of a biofilm. While many of the components needed for biofilm assembly are known, the mechanism by which microbes sense and respond to contact with a surface is poorly understood. Bacillus subtilis is a Gram‐positive model for biofilm formation. The DegS–DegU two‐component system controls several multicellular behaviours in B. subtilis, including biofilm formation. Here we identify the B. subtilis flagellum as a mechanosensor that activates the DegS–DegU regulatory pathway. Inhibition of flagellar rotation by deletion or mutation of the flagellar stator gene, motB, results in an increase in both degU transcription and DegU∼P driven processes, namely exoprotease production and poly‐γ‐dl‐glutamic acid biosynthesis. Similarly, inhibition of flagellar rotation by engaging the flagellar clutch or by tethering the flagella with antibodies also promotes an increase in degU transcription that is reflective of increased DegU∼P levels in the cell. Collectively, these findings strongly indicate that inhibition of flagellar rotation acts as a mechanical trigger to activate the DegS–DegU two‐component signal transduction system. We postulate that inhibition of flagellar rotation could function as a mechanical trigger to activate bacterial signal transduction cascades in many motile bacteria upon contact with a surface.
We Are All Probing Each Other, All the Time
Authors: McCONNELL MIKE
Published: July 2013

The recent scandal of the National Security Agency (NSA) “Hoovering” up the metadata on US and foreign citizens from Google, Facebook and Yahoo exposes in the full light of day the central paradox of the new digital age: The Internet enables us to know and learn more than ever before, but enables more to be known and learned about us by both snooping governments and monetizing information corporations alike.

In this section, Google's Eric Schmidt and Jared Cohen discuss this paradox. We also reprint an interview from 2009 with Mike McConnell, a former chief of the National Security Agency and the driving force behind Booz, Allen, Hamilton's digital security operation. Edward Snowden, the systems administrator who blew the whistle, was employed by the NSA as a subcontractor from Booz, Allen, Hamilton.
Comorbid substance use disorder in schizophrenia: A selective overview of neurobiological and cognitive underpinnings
Authors: Thoma Patrizia , Daum Irene
Published: July 2013

Although individuals with schizophrenia show a lifetime prevalence of 50% for suffering from a comorbid substance use disorder, substance abuse usually represents an exclusion criterion for studies on schizophrenia. This implies that surprisingly little is known about a large group of patients who are particularly difficult to treat. The aim of the present work is to provide a brief and non‐exhaustive overview of the current knowledgebase about neurobiological and cognitive underpinnings for dual diagnosis schizophrenia patients. Studies published within the last 20 years were considered using computerized search engines. The focus was on nicotine, caffeine, alcohol, cannabis and cocaine being among the most common substances of abuse. All drugs of abuse target dopaminergic, glutamatergic and GABAergic transmission which are also involved in the pathophysiology of schizophrenia. Current literature suggests that neurocognitive function might beless disrupted in substance‐abusing compared to non‐abusing schizophrenia patients, but in particular the neuroimaging database on this topic is sparse. Detrimental effects on brain structure and function were shown for patients for whom alcohol is the main substance of abuse. It is as yet unclear whether this finding might be an artifact of age differences of patient subgroups with different substance abuse patterns. More research is warranted on the specific neurocognitive underpinnings of schizophrenia patients abusing distinct psychoactive substances. Treatment programs might either benefit from preserved cognitive function as a resource or specifically target cognitive impairment in different subgroups of addicted schizophrenia patients.
Obstetrical Interventions for Term First Deliveries in the US
Authors: Ananth Cande V. , Wilcox Allen J. , Gyamfi‐Bannerman Cynthia
Published: July 2013

Background

Labour induction and caesarean are increasingly done without clinical indication. However, little is known about the prevalence of such interventions, or the characteristics of women who receive them. We used the 2003 revision of the US birth certificates to summarise recorded interventions and to characterise maternal profiles associated with such interventions.

Methods

We carried out a retrospective study of 2.35 million primiparous women delivering singleton live births at 37–44 weeks in the US from 2005 to 2008. We used the 2003 revision of the birth certificate to define delivery categories: ‘indicated’ were those with induced labour or pre‐labour caesarean for hypertension, diabetes, chorioamnionitis, failed cephalic version at ≥40 weeks, growth restriction (<3rd centile), or post‐term (≥42 weeks); those with pre‐labour caesarean with breech at ≥39 weeks; or those with caesarean with labour lasting ≥12 h, failed trial of labour, vacuum/forceps extraction, or fetal intolerance to labour. Remaining deliveries with induction/caesarean were classified as ‘non‐indicated’ and all other deliveries ‘spontaneous’.

Results

Half of all term first births (50%) were delivered after intervention, and half of interventions were non‐indicated (26% of all deliveries). Women with interventions were more likely to deliver on a weekday. Non‐indicated interventions were more common among socially advantaged women.

Conclusions

Nearly a quarter of US term first deliveries had an indicated intervention, and another quarter received intervention without a recorded clinical indication. Both numbers are probably underestimates.
Effects of sprint interval training on VO2max and aerobic exercise performance: A systematic review and meta‐analysis
Authors: Sloth M. , Sloth D. , Overgaard K. , Dalgas U.
Published: July 2013

Recently, several studies have examined whether low‐volume sprint interval training (SIT) may improve aerobic and metabolic function. The objective of this study was to systematically review the existing literature regarding the aerobic and metabolic effects of SIT in healthy sedentary or recreationally active adults. A systematic literature search was performed (Bibliotek.dk, SPORTDiscus, Embase, PEDro, SveMed+, and Pubmed). Meta‐analytical procedures were applied evaluating effects on maximal oxygen consumption (VO2max). Nineteen unique studies [four randomized controlled trials (RCTs), nine matched‐controlled trials and six noncontrolled studies] were identified, evaluating SIT interventions lasting 2–8 weeks. Strong evidence support improvements of aerobic exercise performance and VO2max following SIT. A meta‐analysis across 13 studies evaluating effects of SIT on VO2max showed a weighted mean effects size of g = 0.63 95% CI (0.39; 0.87) and VO2max increases of 4.2–13.4%. Solid evidence support peripheral adaptations known to increase the oxidative potential of the muscle following SIT, whereas evidence regarding central adaptations was limited and equivocal. Some evidence indicated changes in substrate oxidation at rest and during exercise as well as improved glycemic control and insulin sensitivity following SIT. In conclusion, strong evidence support improvement of aerobic exercise performance and VO2max following SIT, which coincides with peripheral muscular adaptations. Future RCTs on long‐term SIT and underlying mechanisms are warranted.
Clinical presentation and outcome of dengue viral infection in live‐related renal transplant recipients in Karachi, Pakistan
Authors: Nasim A. , Anis S. , Baqi S. , Akhtar S.F. , Baig‐Ansari N.
Published: July 2013

Introduction

In Pakistan, dengue viral infection has become hyper‐endemic. Renal transplantation is also expanding. We aimed to study dengue in renal transplant recipients (RTR).

Methods

We conducted a study of RTR reported to be anti‐dengue immunoglobulin‐M antibody positive from January 2009 to December 2010 at our institution in Karachi and follow their clinical course and outcome.

Results

Median age was 28 years; 75 (73.7%) were males. Clinical presentation included fever in 82 (80.4%), gastrointestinal symptoms in 35 (34.3%), hemorrhagic complications in 9 (8.8%), and thrombocytopenia in 97 (95%), which was of >15 days duration in 24%. Fever was seen less frequently in patients on high‐dose (>7.5 mg) steroids as compared with low‐dose (≤7.5 mg) steroids. Forty‐four patients (43%) had primary and 58 (56.8%) had secondary dengue infection. Dengue fever (DF) occurred in 90 (88%), and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) occurred in 12 (11.7%). DHF/DSS was seen in 3 (6.8%) of those with primary and in 9 (15.5%) of those with secondary infection (P < 0.22). In secondary infection, patients on cyclosporine‐containing regimen had less severe disease, with DHF/DSS in 22% as opposed to DF in 59% (P < 0.04). Of 102 RTR, 68 (66.7%) had graft dysfunction, 5 of whom died. Of the remaining 63, in 54 patients (85.7%) creatinine returned to baseline by an average of 12.6 days. Of 102 patients, 95 (93%) recovered and 7 (6.9%) died, 6 of whom had bacteremia with sepsis and 1 had respiratory failure. None died due to dengue infection alone.

Conclusion

In conclusion, in RTR without life‐threatening co‐morbidities, the clinical course of dengue infection is mild, with good recovery and preserved renal function.
Foreign Wage Premium, Gender and Education: Insights from Vietnam Household Surveys
Authors: Fukase Emiko
Published: July 2013

This paper investigates the differential impacts of foreign ownership on wages for different types of workers (in terms of educational background and gender) in Vietnam using the Vietnam Household Living Standards Surveys of 2002 and 2004. Whereas most previous studies have compared wage levels between foreign and domestic sectors using firm‐level data (thus excluding the informal sector), one advantage of using the Living Standards Surveys in this paper is that the data allow wage comparison analyses to extend to the informal wage sector. A series of Mincerian earnings equations and worker‐specific fixed effects models are estimated. Several findings emerge. First, foreign firms pay higher wages relative to their domestic counterparts after controlling for workers' personal characteristics. Second, the higher the individual workers' levels of education, the larger on average are the wage premiums for those who work for foreign firms. Third, longer hours of work in foreign firm jobs relative to working in the informal wage sector are an important component of the wage premium. Finally, unskilled women experience a larger foreign wage premium than unskilled men, reflecting the low earning opportunities for women and a higher gender gap in the informal wage sector.
On Comparative Engine Performance Testing With Fiber Delivered Laser Ignition and Electrical Ignition
Authors: Wilvert Nick , Joshi Sachin , Yalin Azer
Published: July 2013

Laser ignition of natural gas engines has shown potential to improve many facets of engine performance including brake thermal efficiency, exhaust emissions, and durability as compared with traditional spark ignition. We present proof of concept of a novel fiber optic delivery approach using solid core multimode step index silica fibers with large cladding diameters (400 m core, 720 m cladding). The fibers were able to deliver high beam quality 25 nanosecond pulses of 1064 nm light with 7–10 mJ energy; sufficient to consistently ignite the engine at various air-fuel ratios and loads. Comparative tests between the laser spark plug and a traditional J-gap spark plug were performed on a single cylinder Waukesha Cooperative Fuel Research (CFR) engine running on bottled methane. Performance was measured in terms of the Coefficient of Variation (COV) of Net Mean Effective Pressure (NMEP), fuel specific efficiency, and emissions of oxides of nitrogen (NOx), carbon monoxide (CO), and total hydrocarbons (THC). Tests were run at three different NMEPs of 6, 8, and 12 bar at various air-fuel ratios. Results indicate successful operation of the fiber and improved engine performance at high NMEP and lean conditions.
A Reduced Diesel Surrogate Mechanism for Compression Ignition Engine Applications
Authors: Raju Mandhapati , Wang Mingjie , Senecal P. K. , Som Sibendu , Longman Douglas E.
Published: July 2013

A skeletal mechanism with 117 species and 472 reactions for a Diesel surrogate i.e., n-heptane, was developed. The detailed mechanism for n-heptane created by Lawrence Livermore National Laboratory (LLNL) was employed as the starting mechanism. The detailed mechanism was then reduced with an enhancement of the Direct Relation Graph (DRG) technique called Parallel DRG-with Error Propagation and Sensitivity Analysis (PDRGEPSA). The reduction was performed for pressures from 20 to 80 atm, equivalence ratios from 0.5 to 2, and an initial temperature range of 600–1200 K, covering the compression ignition (CI) engine conditions. Extensive validations were performed against both 0-D simulations with the detailed mechanism and experimental data for spatially homogeneous systems. In order to perform three-dimensional turbulent spray-combustion and engine simulations, the mechanism was integrated with the multi-zone model in the CONVERGE CFD software to accelerate the calculation of detailed chemical kinetics. The Engine Combustion Network (ECN) data from Sandia National Laboratory was used for validation purposes along with single-cylinder Caterpillar engine data. The skeletal mechanism was able to predict various combustion characteristics accurately such as ignition delay and flame lift-off length (LOL) under different ambient conditions. The performance of the multi-zone solver with respect to the full cell-by-cell chemistry solver (SAGE) is compared for the Caterpillar engine simulation and a good match is obtained with significant speed-up of computational time for the multi-zone solver.
Investigation of Low Temperature Combustion Regimes of Biodiesel With n-Butanol Injected in the Intake Manifold of a Compression Ignition Engine
Authors: Soloiu Valentin , Duggan Marvin , Ochieng Henry , Williams David , Molina Gustavo , Vlcek Brian
Published: July 2013

In this study, the in-cylinder soot and NOx trade off was investigated in a Compression Engine by implementing Premixed Charge Compression Ignition (PCCI) coupled with Low Temperature Combustion (LTC) for selected regimes of 1–3 bars IMEP. In order to achieve that, an omnivorous (multi-fuel) single cylinder diesel engine was developed by injecting n-butanol in the intake port while being fueled with biodiesel by direct injection in the combustion chamber. By applying this methodology, the in-cylinder pressure decreased by 25% and peak pressure was delayed in the power stroke by about 8 CAD for the cycles in which the n-butanol was injected in the intake manifold at the engine speed of 800 rpm and low engine loads, corresponding to 1–3 bars IMEP. Compared with the baseline taken with ultra-low sulfur diesel no. 2 (USLD#2), the heat release presented a more complex shape. At 1–2 bars IMEP, the premixed charge stage of the combustion totally disappeared and a prolonged diffusion stage was found instead. At 3 bars IMEP, an early low temperature heat release was present that started 6 degrees (1.25 ms) earlier than the diesel reference heat release with a peak at 350 CAD corresponding to 1200 K. Heat losses from radiation of burned gas in the combustion chamber decreased by 10–50% while the soot emissions showed a significant decrease of about 98%, concomitantly with a 98% NOx reduction at 1 IMEP, and 77% at 3 IMEP, by controlling the combustion phases. Gaseous emissions were measured using an AVL SESAM FTIR and showed that there were high increases in CO, HC and NMHC emissions as a result of PCCI/LTC strategy; nevertheless, the technology is still under development. The results of this work indicate that n-butanol can be a very promising fuel alternative including for LTC regimes.
Pressure Sensitivity of HCCI Auto-Ignition Temperature for Oxygenated Reference Fuels
Authors: Truedsson Ida , Tuner Martin , Johansson Bengt , Cannella William
Published: July 2013

The current research focuses on creating an HCCI fuel index suitable for comparing different fuels for HCCI operation. One way to characterize a fuel is to use the Auto-Ignition Temperature (AIT). The AIT can be extracted from the pressure trace. Another potentially interesting parameter is the amount of Low Temperature Heat Release (LTHR) that is closely connected to the ignition properties of the fuel.

The purpose of this study was to map the AIT and amount of LTHR of different oxygenated reference fuels in HCCI combustion at different cylinder pressures. Blends of n-heptane, iso-octane and ethanol were tested in a CFR engine with variable compression ratio. Five different inlet air temperatures ranging from 50°C to 150°C were used to achieve different cylinder pressures and the compression ratio was changed accordingly to keep a constant combustion phasing, CA50, of 3±1° after TDC. The experiments were carried out in lean operation with a constant equivalence ratio of 0.33 and with a constant engine speed of 600 rpm.

The amount of ethanol needed to suppress LTHR from different PRFs was evaluated. The AIT and the amount of LTHR for different combinations of n-heptane, iso-octane and ethanol were charted.
Low Temperature Gasoline Combustion With Diesel Micro-Pilot Injection in a Six-Cylinder Heavy Duty Engine
Authors: Bach Florian , Hampe Clemens , Wagner Uwe , Spicher Ulrich , Sauer Christina
Published: July 2013

This paper describes the operation of a heavy duty six-cylinder engine in a dual fuel, Low Temperature Combustion (LTC) mode with very low engine-out NOx und soot emissions according to the US EPA Tier IV final emission limits in the corresponding C1 test cycle. This operation mode makes use of a short pilot injection of diesel fuel, which is injected directly into the cylinder, to ignite a highly diluted, premixed gasoline air mixture. Multicylinder engine operation could be demonstrated over the entire engine operating map with loads of up to 2 MPa BMEP. Expensive aftertreatment systems for NOx and soot emissions are not required.

This paper also discusses the challenges involved with the implementation of this combustion system on a multicylinder engine. When transferring the dual fuel LTC from a single cylinder research engine to a multicylinder engine, the design of some engine components, e.g. the camshaft and the piston, were changed. The intake manifold is modified with port fuel injectors for ideal gasoline mixture preparation and equal distribution to all cylinders. To avoid cylinder imbalances, it is possible to control the injected masses of gasoline and diesel fuel for the pilot injection on a per-cylinder basis. Achieving high dilution for ignition delay via EGR and boosted intake pressure to avoid high pressure rise rates and knocking presents challenges for the two-stage turbocharger design. Additionally, high EGR rates and EGR cooling for increased loads are addressed. Finally, experiments to determine the significant control parameters for the combustion process are performed on the engine.

In the course of these investigations, dual fuel LTC could be transferred from a single cylinder research engine to a multicylinder engine; previously obtained single-cylinder operating conditions could be achieved even at high loads.
Development of a Piston Secondary Motion Model for Skirt Friction Analysis
Authors: Gunelsu Ozgur , Akalin Ozgen
Published: July 2013

A comprehensive piston skirt lubrication and secondary motion model that can be used for piston friction simulations was developed based on Greenwood and Tripp’s surface asperity contact model and Patir and Cheng’s modified Reynolds equation with surface flow factors. Oil flow between the skirt-liner clearances was modeled and hydrodynamic and asperity contact pressures around the skirt were calculated. Reynolds boundary conditions were applied to determine the film rupture boundaries and wetted areas. Surface roughness and roughness orientation were included in the model. Due to its important effect on pressure development in the oil film, change in the skirt profile due to elastic deformations was taken into account. Change of the skirt profile due to piston thermal expansion is also calculated using the steady-state temperature distribution of the piston corresponding to the investigated engine running conditions. A piston stiffness matrix obtained by finite element analysis was used to determine the elastic deformations of the piston skirt under the calculated oil film pressures. A two-degree-of-freedom system is formed with the forces and moments calculated by the lubrication model. These forces and moments require a coupled solution with piston position. This is achieved by applying an iterative numerical procedure based on Broyden’s scheme which seeks force and moment balance at each iteration phase making use of time step variation. The effects of various engine operating conditions and piston design parameters on piston secondary motion were investigated. Piston skirt friction force due to hydrodynamic shear forces and metal-to-metal contact is calculated.
Simulation of an Intake Manifold Pre-Heater for Cold Engine Startup
Authors: Kreun Patrick K. , Fajardo Claudia M. , Baumann Andreas S.
Published: July 2013

Ensuring consistent, reliable diesel engine startups in cold temperatures is of utmost importance in a number of applications. Under extreme temperatures, the use of glow plugs is complemented by intake manifold heaters. In these, the energy released from combustion increases the intake air temperature before the air enters the main combustion chamber. Since the process also alters the stoichiometry of the fuel-air mixture at the intake ports, the pre-heater operation must be optimized in order to guarantee successful and reliable in-cylinder combustion during engine startups. This paper describes the development of an intake manifold model incorporating an air pre-heater for application in a diesel engine. The model, created using a commercial one-dimensional simulation tool, was validated against experimental data and subsequently used to quantify the concentration of combustion product species at the intake runners, as well as intake charge dilution. Results showed that the effective equivalence ratio might increase up to 2.6 after the first 25 seconds of cranking, with 12.5% reduction of the O2 concentration in the intake charge.
Real-Time Monitoring of Combustion Instability in a Homogeneous Charge Compression Ignition (HCCI) Engine Using Cycle-by-Cycle Exhaust Temperature Measurements
Authors: Gardiner David P. , Neill W. Stuart , Chippior Wallace L.
Published: July 2013

This paper describes an experimental study concerning the feasibility of monitoring the combustion instability levels of an HCCI engine based upon cycle-by-cycle exhaust temperature measurements. The test engine was a single cylinder, four-stroke, variable compression ratio Cooperative Fuel Research (CFR) engine coupled to an eddy current dynamometer. A rugged exhaust temperature sensor equipped with special signal processing circuitry was installed near the engine exhaust port. Reference measurements were provided by a laboratory grade, water-cooled cylinder pressure transducer. The cylinder pressure measurements were used to calculate the Coefficient of Variation of Indicated Mean Effective Pressure (COV of IMEP) for each operating condition tested.

Experiments with the HCCI engine confirmed that cycle-by-cycle variations in exhaust temperature were present, and were of sufficient magnitude to be captured for processing as high fidelity signal waveforms. There was a good correlation between the variability of the exhaust temperature signal and the COV of IMEP throughout the operating range that was evaluated. The correlation was particularly strong at the low levels of COV of IMEP (2–3%), where production engines would typically operate.

A real-time combustion instability signal was obtained from cycle-by-cycle exhaust temperature measurements, and used to provide feedback to the fuel injection control system. Closed loop operation of the HCCI engine was achieved in which the engine was operated as lean as possible while maintaining the COV level at or near 2.5%.
Performance of Rotating Rough Circular Step Bearing: Characteristic of Lubrication at Nano Scale
Authors: Deheri G. M. , Dave P. R. , Himanshu Chimanlal Patel
Published: July 2013

An endeavor has been made to investigate the effect of transverse surface roughness on the behaviour of thin film lubrication at nano scale of a magnetic fluid based rough porous rotating circular step bearing. Mainly, the combination of the properties of the surfaces, the lubricant and viscosity of the lubricant are responsible for thin film lubrication between two rough surfaces in relative motion. The effects induced by the transverse roughness and the couple stress cannot be disregarded in the regime while the ordered molecules dominate the fluid field. The random roughness of the surfaces is characterized by a random variable with non zero mean, variance and skewness. The associated Reynolds’ equation is then stochastically averaged and solved with appropriate boundary conditions to obtain the pressure distribution, leading to the calculation of load carrying capacity. It is easily observed that basically, the magnetic fluid lubricant combined with the couple stress effect is responsible for the improved performance of the bearing system. It is clearly seen that the adverse effect of transverse roughness is relatively less when considered with thin film lubrication at nano scale. The increased load carrying capacity due to variance (-ve) gets further increased due to negatively skewed roughness which becomes more pronounced owing to thin film lubrication at the nano scale. It is seen that the existence of couple stress enhances the load carrying capacity. In addition, the characteristic length contributing to the couple stress increases load carrying capacity considerably. Even, size dependent effects are noticed in the lubrication with couple stress while the thinner the lubrication film the more obvious is the effect.
Friction Force Distribution Along Time-Varying Contact Line in Helical Gear System
Authors: Li Wen-liang , Wang Li-qin
Published: July 2013

Based on the theory of energy minimization, a numerical algorithm was developed to calculate friction force distribution along the time-varying contact line in helical gear system. The friction force distribution varies with the instantaneous position of the meshing point and the length of contact line. The friction force was calculated on every meshing point of time-varying contact line via the algorithm. The results show the friction force becomes larger from the tooth root to the pitch point and becomes smaller from the pitch point to the tooth tip. Due to this, there is a significant shock at the pitch point which will generate noise and vibration. The changing law of friction force distribution provides a fundamental theory for modification shape design and impact reduction.
Contact Analyses for Anisotropic Half Space With an Anisotropic Coating
Authors: Bagault C. , Nélias D. , Baietto M.-C. , Ovaert T.
Published: July 2013

For most composite and mono-crystal materials their compositions or the elaboration and manufacturing processes imply that it exists one or two main directions or even a general anisotropy. Moreover, coatings are often used to prevent or control wear. Coatings do not have, generally, the same properties as the substrate and may have various thicknesses. The influence of the anisotropy orientations (in the coating and in the substrate) have to be taken into account to better predict the distribution of the contact pressure and the subsurface stress-field in order to optimize the service life of industrial components. A contact model using semi analytical methods, relying on elementary analytical solutions, has been developed. It is based on numerical techniques adapted to contact mechanics. Recent developments aim to quantify displacements and stresses of a layered anisotropic elastic half space which is in contact with a rigid sphere. The influence of material properties and layer thickness on the contact problem solution will be more specifically analyzed.
Tribological Effects of BN and MoS2 Nanoparticles Added to Polyalphaolefin Oil in Piston Skirt/Cylinder Liner Tests
Authors: Demas Nicholaos G. , Timofeeva Elena V. , Routbort Jules L. , Fenske George R.
Published: July 2013

In this work, the friction and wear of poly-alpha-olefin (PAO10) base oil with 3 wt. % boron nitride (BN), and molybdenum disulfide (MoS2) nanoparticles were studied. The formulations were tested using cast iron cylinder-liner segments reciprocating against aluminum alloy piston-skirt segments at 20, 40, and 100°C. The results showed that at a load of 250 N and reciprocating frequency of 2 Hz BN did not lower friction, whereas MoS2 nanoparticles were very effective at reducing both friction and wear, compared to the base oil. Raman spectroscopy showed the formation of an aligned MoS2 layer on the cast iron liner surface, which functioned as a tribofilm. In the case of the cast iron liner tested with BN nanolubricant there were no traces of BN that could be related to tribofilm formation. The effect of surfactant was also studied and it was found that not only it was beneficial in dispersing the nanoparticles in oil, but also produced some reduction in friction and wear even as stand-alone additive in PAO10.
Performance of Different Microtexture Shapes for Textured Gas Lubricated Parallel Slider Bearings
Authors: Qiu Mingfeng , Raeymaekers Bart
Published: July 2013

The tribological performance of different microtexture shapes is evaluated for the case of gas lubricated textured parallel slider bearings. The geometry of each shape is optimized in terms of load carrying capacity, after which the performance of different shapes is compared relative to each other. The ellipsoidal shape is found to generate the largest load carrying capacity.
Crack Detection in a Rotor Dynamic System by Vibration Monitoring: Analysis and Experimental Results
Authors: Varney Philip , Green Itzhak
Published: July 2013

As the power to weight ratio demand on rotordynamic systems increases, susceptibility to transverse fatigue cracking of the shaft increases as well. The ability to detect cracks in an early stage of progression is imperative for minimizing off-line repair time. A vibration monitoring system proposed prior is developed herein, employing the 2X harmonic response component of the rotor tilt as a signature indicating a transverse shaft crack. To effectively capture the 2X response, the crack model must include the local nature of the crack, the depth of the crack, and the stiffness asymmetry inducing the gravity-forced 2X harmonic response. The transfer matrix technique is well-suited to incorporate these crack attributes due to its modular nature. Two transfer matrix models are proposed to predict the 2X harmonic response. The first model applies local crack flexibility coefficients determined using the strain energy release rate, while the second incorporates the crack as a rectangular notch to emulate a manufactured crack used in the experiments. Analytic results are then compared to experimental measurement of the rotor tilt gleaned from an overhung rotor test rig originally designed to test seal face dynamics. The test rig is discussed, and experimental 2X harmonic amplitudes of the rotor tilt are provided for shafts containing manufactured cracks of depths between zero and 40 percent.
Molecular Dynamics Simulation of Confined n-Alkanes Between Nano-Asperity Walls
Authors: Zheng Xuan , Zhu Hongtao , Tieu A. Kiet
Published: July 2013

A molecular dynamics simulation of confined n-alkanes is conducted to investigate the effect of chain length (C8, C16, C32, C64) and normal load (250, 500, 750, 1000MPa) on friction and asperity contact. The results indicate that the longer chain n-alkanes maintain more monolayer atoms in the asperity contact interface than the shorter ones and as a result significantly reduce the friction force. Under a normal load of 250MPa, the asperity with C32 and C64 are separated by the lubricant with less metal contact. Periodic friction force is observed and it correlates with the deformation of the local lattice that breaks and relocates the atoms during the asperity contact.
Effect of Proteins on Film Formation in Bovine Serum Lubricated Contacts Under Rolling/Sliding Conditions
Authors: Vrbka Martin , Navrat Tomas , Krupka Ivan , Hartl Martin , Gallo Jiri
Published: July 2013

The aim of this study is to perform detail experimental mapping of the lubricating film thickness of bovine serum (BS) within the contact between an artificial metal or ceramic femoral head and a glass disc and analyze effect of proteins on the film formation under rolling/sliding conditions.

The film thickness was studied experimentally using an optical test rig as a function of time under variety of constant mean speeds. Chromatic interferograms were recorded with a high-speed digital camera and evaluated with thin film colorimetric interferometry.

Under pure rolling conditions it was observed that the central film thicknesses increased with time for all measurements. When the disc was slower than head then the measured central film thicknesses achieved values only about some few nanometres, whereas when the tests were realized with faster disc then measured central film thicknesses achieved significantly higher values. Distribution of the film thickness within the contact zone is not homogeneous and two different film thickness regions can be found; thicker protein film and thinner base film that both show specific behaviour over time.

This study showed that protein formation plays an important role in the lubrication processes of artificial joints of the human. Due to challenging of this study the more complex research work is carried out at the present time.
Superlubricity Mechanism of Brasenia Schreberi Mucilage
Authors: Li Jinjin , Luo Jianbin
Published: July 2013

An eatable aquatic plant, Brasenia schreberi, was found owning excellent lubrication properties with an ultra-low friction coefficient about 0.005 between its surface and a glass surface. The friction coefficient is closely related to the structure of mucilage and the content of water in the mucilage. Many nano-sheets were found in the mucilage surrounding the Brasenia schreberi. The lubrication mechanism is proposed due to forming hydration layer among these nano-sheets with plenty of bond water molecules. The excellent lubrication property has obvious application for the fabrication of glossy pill coated by such kind of mucilage, which would prevent pill lodging in people’s throat, especially for children.
Elastohydrodynamic Piston Skirt Lubrication: Effect on Tribological Performances
Authors: Abbes Miloud Tahar , Maspeyrot Patrick , Dekkiche Ahmed , Benbrik Mohamed , Hacène Fouad Boukli
Published: July 2013

A model of elastohydrodynamic lubrication of piston skirt is developed in this paper. The secondary motion of the piston, the lubrication and the elastic deformations of skirt and cylinder are described by a transient strongly nonlinear system coming from the coupling of the dynamics equations of piston secondary motion and the Reynolds equation. The iterative Newton-Raphson method in conjunction with Murty’s algorithm for cavitation was used to solve the problem. An optimum skirt curved profile, which maintain piston in optimum performance characteristics, is adopted. Using the tribological performance of the lubricated skirt-cylinder, the results — minimum oil-film thickness, maximum pressure in the lubricant film and friction — are compared to the elastohydrodynamic solution and the rigid skirt-cylinder solution. The effect of elastic deformation of both skirt and cylinder show that elastohydrodynamic analysis is necessary for an accurate prediction of a piston-cylinder performance. The computational work, applied to a solid skirt piston of a V-8 direct injection diesel engine truck, should be a powerful design analysis tool, which can be used to increase the available engine power through optimum piston performance characteristics.
Non-Linear Analysis of Floating Ring Annular Seals
Authors: Arghir Mihai
Published: July 2013

The present paper is a continuation of a previous work [1] tackling the analysis of floating ring annular seals. A quasi-analytic solution of the floating ring motion was developed in [1] but its stability was not addressed. This stability problem of the floating ring driven by the uniform circular precession of the rotor is answered in the present work.