bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser sintered body armour – establishing single layer stab protection
Authors: Johnson Andrew Allan , Bingham Guy , Majewski Candice
Published: November 2017

Purpose

The purpose of this paper is to establish the minimum thickness required to provide stab protection in accordance with the United Kingdom Home Office Scientific Development Branch (HOSDB) standards while testing a series of laser sintered (LS) planar specimens using instrumented test apparatus.

Design/methodology/approach

Planar test specimens were LS in single-layer thicknesses ranging from 1.00 to 15.00 mm in four material powder categories – DuraForm® virgin, DuraForm 50/50 mix, DuraForm EX® virgin and DuraForm EX 50/50 mix. All specimens were tested using instrumented drop test apparatus and were impacted with established Stanley Tools 1992 trimming blades to the UK HOSDB KR1-E1 stab impact energy level.

Findings

The research demonstrated that a minimum single planar specimen thickness of 11.00 mm, manufactured from DuraForm EX 50/50 mix powder, was required to provide protection against the HOSDB KR1-E1 level of stab impact energy. The alternative powder mixes tested within this experiment demonstrated poor levels of stab protection, with virgin powder specimens demonstrating no protection up to 15.00 mm, whereas DuraForm 50/50 mix specimens demonstrating inconsistent performances.

Originality/value

This paper enhances on existing literature surrounding the manufacturing and testing of additive manufacturing (AM) stab-resistant armour by adding further rigour to the testing of AM body armour specimens. In addition, this research establishes key foundation characteristics which could be utilised for the future development of bespoke AM body armour garments.
Targeted gene sequencing and whole‐exome sequencing in autopsied fetuses with prenatally diagnosed kidney anomalies
Authors: Rasmussen M. , Sunde L. , Nielsen M.L. , Ramsing M. , Petersen A. , Hjortshøj T.D. , Olsen T.E. , Tabor A. , Hertz J.M. , Johnsen I. , Sperling L. , Petersen O.B. , Jensen U.B. , Møller F.G. , Petersen M.B. , Lildballe D.L.
Published: November 2017

Identification of fetal kidney anomalies invites questions about underlying causes and recurrence risk in future pregnancies. We therefore investigated the diagnostic yield of next‐generation sequencing in fetuses with bilateral kidney anomalies and the correlation between disrupted genes and fetal phenotypes. Fetuses with bilateral kidney anomalies were screened using an in‐house‐designed kidney‐gene panel. In families where candidate variants were not identified, whole‐exome sequencing was performed. Genes uncovered by this analysis were added to our kidney panel. We identified likely deleterious variants in 11 of 56 (20%) families. The kidney‐gene analysis revealed likely deleterious variants in known kidney developmental genes in 6 fetuses and TMEM67 variants in 2 unrelated fetuses. Kidney histology was similar in the latter 2 fetuses—presenting a distinct prenatal form of nephronophthisis. Exome sequencing identified ROBO1 variants in one family and a GREB1L variant in another family. GREB1L and ROBO1 were added to our kidney‐gene panel and additional variants were identified. Next‐generation sequencing substantially contributes to identifying causes of fetal kidney anomalies. Genetic causes may be supported by histological examination of the kidneys. This is the first time that SLIT‐ROBO signaling is implicated in human bilateral kidney agenesis.
Pharmacogenetics: A strategy for personalized medicine for autoimmune diseases
Authors: Tavakolpour S. , Darvishi M. , Ghasemiadl M.
Published: November 2017

For many years, a considerable number of patients with autoimmune diseases (ADs) have suffered from a lack of drug response and drug‐related toxicity. Despite the emergence of new therapeutic options such as biological agents, patients continue to struggle with these problems. Unfortunately, new challenges, including the paradoxical effects of biological drugs, have complicated the situation. In recent decades, efforts have been made to predict drug response as well as drug‐related side effects. Thanks to the many advances in genetics, evaluation of markers to predict drug response/toxicity before the initiation of treatment may be an avenue toward personalizing treatments. Implementing pharmacogenetics and pharmacogenomics in the clinic could improve clinical care; however, obstacles remain to effective personalized medicine for ADs. The present study attempted to clarify the concept of pharmacogenetics/pharmacogenomics for ADs. After an overview on the pathogenesis of the most common types of treatments, this paper focuses on pharmacogenetic studies related to the selected ADs. Bridging the gap between pharmacogenetics and personalized medicine is also discussed. Moreover, the advantages, disadvantages and recommendations related to making personalized medicine practical for ADs have been addressed.
THE IMPACT OF STOCK MARKET FLUCTUATIONS ON THE MENTAL AND PHYSICAL WELL‐BEING OF CHILDREN
Authors: Cotti Chad , Simon David
Published: November 2017

The stock market crash of 2008 caused a severe impact to households. Earlier research has explored the impacts of a stock market crash on life well‐being, psychological stress, and adult health behaviors. We extend this literature by documenting impacts of stock market fluctuations on a range of child outcomes; including effects on both mental and physical health. We show a negative effect of a market crash on hospitalizations, child reported health status, sick days from school, and an aggregate health index measure. Both graphical and regression‐based analysis reveal that our results are not driven by a preexisting trend of declining child health before the market crash and extensive sensitivity analysis demonstrates that the results are robust to multiple empirical specifications. (JEL I15, E32, J13)
A nationwide epidemiological study of myasthenia gravis in Latvia
Authors: Zieda A. , Ravina K. , Glazere I. , Pelcere L. , Naudina M. S. , Liepina L. , Kamsa I. , Kurjane N. , Woodhall M. , Jacobson L. , Leite M. I. , Tandon K. , Kenina V.
Published: November 2017

Background and purpose

Myasthenia gravis (MG) is an autoimmune disorder characterized by fatigable muscle weakness due to antibody‐mediated impairment of neuromuscular transmission. The aim of this study was to investigate the incidence and prevalence of MG in Latvia, and to characterize this population by well‐established clinical parameters such as age at onset, presence of associated antibodies and thymus pathology.

Methods

All prevalent cases on 1 January 2015 and cases of patients newly presenting with MG symptoms from 1 January 2010 to 31 December 2014 were selected from the database of the Neuromuscular Disease Clinic of Pauls Stradins Clinical University Hospital and Children's Clinical University Hospital. Crude rates were calculated based on population data. These were directly age‐standardized to the European and World Health Organization world standard populations. The analysis of clinical characteristics was carried out in a cohort of patients who had undergone a complete set of electrophysiological, serological and radiological investigations (n = 153; 68%).

Results

During the study period 99 incident and 226 prevalent cases were identified. The total crude MG incidence was 9.7 per million person‐years. The prevalence of MG on 1 January 2015 was 113.8 per million. 54.2% of patients tested positive for acetylcholine receptor antibodies, 7.8% for muscle specific kinase antibodies and 1.3% for lipoprotein related protein 4 antibodies.

Conclusions

This is the first study of MG in Latvia and the second population‐based study of MG in Eastern Europe. Our epidemiological results are similar to those in some other European and Northern American countries, and show high prevalence and increasing incidence of late‐onset MG.
Vessel noise cuts down communication space for vocalizing fish and marine mammals
Authors: Putland Rosalyn L. , Merchant Nathan D. , Farcas Adrian , Radford Craig A.
Published: November 2017

Anthropogenic noise across the world's oceans threatens the ability of vocalizing marine species to communicate. Some species vocalize at key life stages or whilst foraging, and disruption to the acoustic habitat at these times could lead to adverse consequences at the population level. To investigate the risk of these impacts, we investigated the effect of vessel noise on the communication space of the Bryde's whale Balaenoptera edeni, an endangered species which vocalizes at low frequencies, and bigeye Pempheris adspersa, a nocturnal fish species which uses contact calls to maintain group cohesion while foraging. By combining long‐term acoustic monitoring data with AIS vessel‐tracking data and acoustic propagation modelling, the impact of vessel noise on their communication space was determined. Routine vessel passages cut down communication space by up to 61.5% for bigeyes and 87.4% for Bryde's whales. This influence of vessel noise on communication space exceeded natural variability for between 3.9 and 18.9% of the monitoring period. Additionally, during the closest point of approach of a large commercial vessel, <10 km from the listening station, the communication space of both species was reduced by a maximum of 99% compared to the ambient soundscape. These results suggest that vessel noise reduces communication space beyond the evolutionary context of these species and may have chronic effects on these populations. To combat this risk, we propose the application or extension of ship speed restrictions in ecologically significant areas, since our results indicate a reduction in sound source levels for vessels transiting at lower speeds.
Microstructure and indentation damage resistance of ZrB2‐20 vol.%SiC ipo‐eutectic composites
Authors: Zhou Jiamin , Zhu Degui , Zhang Haiwen , Bogomol Iurii , Grasso Salvatore , Hu Chunfeng
Published: November 2017

Zirconium diboride with 20 vol.% silicon carbide bulk composites were fabricated using directionally solidification (DS) and also by spark plasma sintering (SPS) of crushed DS ingots. During the DS the cooling front aligned the c‐axis of ZrB2 grains and its Lotgering factor of f(00l) was high as 0.98. The Vickers hardness was anisotropic and it was high as 17.6 GPa along the c‐axis and 15.3 GPa when measured in an orthogonal direction. On both surfaces, even when using 100 N indentation load, no cracks were observed, suggesting a very high resistance to crack propagation. Such anomalous behavior was attributed to the hierarchical structure of DS sample where the ZrB2 phase was under strong compression and the SiC phase was in tension. In the SPSed sample, the microstructure was isotropic respect to the direction of applied pressure. Indentation cracks appeared around the indent corners but not emanated from the diagonals, confirming high damage resistance.
Violent Poly‐Victimization: The Longitudinal Patterns of Physical and Emotional Victimization Throughout Adolescence (11–17 Years)
Authors: Obsuth Ingrid , Mueller Johnson Katrin , Murray Aja Louise , Ribeaud Denis , Eisner Manuel
Published: November 2017

In this study, we aimed to characterize developmental patterns of poly‐victimization in a normative sample of adolescents by applying longitudinal latent class analysis. Using the four most recent waves of data from the Zurich Project on the Social Development of Children and Youths (z‐proso), we identified three classes, or separate groups, of youths with distinct patterns of victimization from age 11 to 17. The largest class represented young people who were least likely to be victimized in any way and at any time. The two smaller groups represented different types of poly‐victimization—a non‐parental and a long‐term parental victimization group. Adolescents in the two groups differed both in the number as well as type of victimization that they experienced at different times. Moreover, class membership also had implications for different mental health outcomes.
Foreign and Domestic Collaboration, Product Innovation Novelty, and Firm Growth
Authors: Hsieh Wan‐Lin , Ganotakis Panagiotis , Kafouros Mario , Wang Chengqi
Published: November 2017

Although prior research underscores the benefits of external collaboration for a firm's innovative output, little research has examined the role that collaboration plays across the different stages of the innovation process. Drawing from organizational learning theory, this article examines (1) how collaboration with domestic partners assists in the formation of collaborations with foreign partners, (2) how knowledge from these collaborations is associated with product innovation at different levels of novelty, and (3) how the relationship between the level of innovation novelty and firm growth is influenced by whether the focal firm engages in open or closed innovation and the origin of the collaborator (foreign or domestic). Three key findings emerge from the econometric analysis of a sample of 1684 Taiwanese firms. First, domestic collaborations assist in the formation of foreign collaborations when the partner type is the same. Second, the level of innovation novelty is associated with the type and geographic location of partners. This study differentiates among noninnovating firms, incremental innovators, and radical innovators and demonstrates that the role of partners changes as the number of countries in which a firm collaborates with each partner type increases. Third, only radical innovation is relevant to firm growth, regardless of whether it is developed internally or through collaboration with domestic or foreign partners.
The Sleep Condition Indicator: reference values derived from a sample of 200 000 adults
Authors: Espie Colin A. , Farias Machado Pedro , Carl Jenna R. , Kyle Simon D. , Cape John , Siriwardena A. Niroshan , Luik Annemarie I.
Published: November 2017

The Sleep Condition Indicator (SCI) is an eight‐item rating scale that was developed to screen for insomnia disorder based on DSM‐5 criteria. It has been shown previously to have good psychometric properties among several language translations. We developed age‐ and sex‐referenced values for the SCI to assist the evaluation of insomnia in everyday clinical practice. A random sample of 200 000 individuals (58% women, mean age: 31 ± 13 years) was selected from those who had completed the SCI via several internet platforms. Descriptive and inferential methods were applied to generate reference data and indices of reliable change for the SCI for men and women across the age deciles 16–25, 26–35, 36–45, 46–55, 56–65 and 66–75 years. The mean SCI score for the full sample was 14.97 ± 5.93. Overall, women scored worse than men (14.29 ± 5.83 versus 15.90 ± 5.94; mean difference: −1.60, η2 = 0.018, Cohen's d = 0.272) and those of older age scored worse than those younger (−0.057 points per year, 95% confidence interval (CI): −0.059 to −0.055) relative to age 16–25 years. The Reliable Change Index was established at seven scale points. In conclusion, the SCI is a useful instrument for clinicians and researchers that can help them to screen for insomnia, compare completers to individuals of similar age and sex and establish whether a reliable change was achieved following treatment.
Continuous Lubricant Film Thickness Measurement Between Piston Ring and Cylinder Bore
Authors: Ayranci Yunus Emre , Akalin Ozgen
Published: November 2017

Measurement of film thickness between piston ring and cylinder bore has been a challenge for decades; laser induced fluorescence method (LIF) was used by several groups and promising results are obtained for the investigation of lubricant film transport. In this study, blue light generated by a laser source is transmitted to a beam splitter by means of a fiber optic cable and combined with another fiber optic line, then transmitted to the piston ring and cylinder bore conjunction. The light causes the fluorescence dye present in the lubricant to emit light in a longer wavelength, i.e. green. Reflected light is recollected; blue wavelength components are filtered out using a narrow band pass optical filter, and only components in the florescence wavelength is transmitted to a photomultiplier tube. The photomultiplier produces a voltage proportional instantaneous lubricant film thickness. Then, the photomultiplier signal is calibrated for lubricant film thickness using a laser textured cylinder bore with known geometries. Additional marks were etched on the liner for calibration. The LIF system is adapted to a piston ring and cylinder bore friction test system simulating engine conditions. Static piston ring and reciprocating liner configuration of the bench test system allows the collection of continuous lubricant film thickness data as a function of crank angle position. The developed system has potential to evaluate new designs, materials and surface properties in a controlled and repeatable environment.
An Experimental Investigation of Early Flame Development in an Optical SI Engine Fueled With Natural Gas
Authors: Dumitrescu Cosmin E. , Padmanaban Vishnu , Liu Jinlong
Published: November 2017

Improved internal combustion (IC) engine simulations of natural gas (NG) combustion under conventional and advanced combustion strategies have the potential to increase the use of NG in the transportation sector in the United States. This study focused on the physics of turbulent flame propagation. The experiments were performed in a single-cylinder heavy-duty compression-ignition (CI) optical engine with a bowl-in piston that was converted to spark ignition (SI) NG operation. The size and growth rate of the early flame from the start of combustion until the flame filled the camera field-of-view were correlated to combustion parameters determined from in-cylinder pressure data, under low-speed, lean-mixture, and medium-load conditions. Individual cycles showed evidence of turbulent flame wrinkling, but the cycle-averaged flame edge propagated almost circular in the 2D images recorded from below. More, the flame-speed data suggested a different flame propagation inside a bowl-in piston geometry compared to a typical SI engine chamber. For example, while the flame front propagated very fast inside the piston bowl, the corresponding mass fraction burn was small, which suggested a thick flame region. In addition, combustion images showed flame activity after the end of combustion inferred from the pressure trace. All these findings support the need for further investigations of flame propagation under conditions representative of CI engine geometries, such as those in this study.
Capturing Pressure Oscillations in Numerical Simulations of Internal Combustion Engines
Authors: Gubba Sreenivasa Rao , Jupudi Ravichandra S. , Pasunurthi Shyam Sundar , Wijeyakulasuriya Sameera D. , Primus Roy J. , Klingbeil Adam , Finney Charles E. A.
Published: November 2017

In an earlier publication [1] the authors compared numerical predictions of the mean cylinder pressure of diesel and dual-fuel combustion, to that of measured pressure data from a medium-speed, large-bore engine. In these earlier comparisons, measured data from a flush-mounted in-cylinder pressure transducer showed notable and repeatable pressure oscillations which were not evident in the mean cylinder pressure predictions from CFD. In this paper, the authors present a methodology for predicting and reporting the local cylinder pressure consistent with that of a measurement location. Such predictions for large-bore, medium-speed engine operation demonstrate pressure oscillations in accordance with those measured. The temporal occurrences of notable pressure oscillations were during the start of combustion and around the time of maximum cylinder pressure. With appropriate resolutions in time steps and mesh sizes, the local cell static pressure predicted for the transducer location showed oscillations in both diesel and dual-fuel combustion modes which agreed with those observed in the experimental data. Fast Fourier Transform (FFT) analysis on both experimental and calculated pressure traces revealed that the CFD predictions successfully captured both the amplitude and frequency range of the oscillations. Resolving propagating pressure waves with the smaller time steps and grid sizes necessary to achieve these results required a significant increase in computer resources.
Optimization of the Charge Motion in Internal Combustion Engines Driven by Sewage Gas for CHP-Units
Authors: Konstantinoff Lucas , Möltner Lukas , Pillei Martin , Steiner Thomas , Dornauer Thomas , Herdin Günther , Mairegger Dominik
Published: November 2017

In this study, the influence of the charge motion on the internal combustion in a spark ignition sewage gas-driven engine (150 kW) for combined heat and power units was investigated. For this purpose, the geometry of the combustion chamber in the immediate vicinity to the inlet valve seats was modified. The geometrical modification measures were conducted iteratively by integrative determination of the swirl motion on a flow bench, by laser-optical methods and consecutively by combustion analysis on a test engine. Two different versions of cylinder heads were characterized by dimensionless flow and swirl numbers prior to testing their on-engine performance. Combustion analysis was conducted with a cylinder pressure indication system for partial and full load, meeting the mandatory NOx limit of 500 mg m−3. Subsuming the flow bench results, the new valve seat design has a significant enhancing impact on the swirl motion but it also leads to disadvantages concerning the volumetric efficiency. A comparative consideration of the combustion rate delivers that the increased swirl motion results in a faster combustion, hence in a higher efficiency. In summary, the geometrical modifications close to the valve seat result in increased turbulence intensity. It was proven that this intensification raises the ratio of efficiency by 1.6%.
Predicting Ignition and Combustion of a Pilot Ignited Natural Gas Jet Using Numerical Simulation Based on Detailed Chemistry
Authors: Jud Michael , Fink Georg , Sattelmayer Thomas
Published: November 2017

In this paper, a multidimensional computational fluid dynamics (CFD) model coupled with detailed chemistry calculations was used to analyze dual-fuel combustion based on high pressure direct injection of natural gas. The main focus was to analyze the capability of predicting pressure curve and heat release rate (HRR) for different injection strategies. Zero-dimensional homogeneous constant volume reactor calculations were used to select a reaction mechanism for the temperature range below 800 K. As the best-performing mechanism, the Chalmers mechanism was chosen. To validate the numerical model, the setup was first split into a single gas injection and a single Diesel injection. They were validated individually using shadowgraphs obtained from a Rapid Compression Expansion Machine (RCEM). Diesel ignition timing and position in the combustion chamber were close to experimental results. Gas direct injection showed good agreement with regard to penetration and mixing. In the dual-fuel setup, the injection timing of natural gas was varied to create a first case with mainly diffusive combustion and a second case with mainly premixed combustion of natural gas. For both setups good agreement with pressure curve and heat release rate were achieved. A qualitative comparison of shadowgraphs with the density field highlights the important points to predict dual-fuel combustion.
Engine Strategies to Meet Phase-2 Greenhouse Gas Emission Legislation for Heavy-Duty Diesel Engines
Authors: Joshi Satyum , Dahodwala Mufaddel , Koehler Erik , Franke Michael
Published: November 2017

In 2027, the fully phased-in EPA/NHTSA Phase-2 greenhouse gas (GHG) emission legislation for heavy-duty (HD) diesel engines will mandate a 5.1% reduction in fuel consumption for MY2017 tractor engines and a 4.2% reduction in fuel consumption for MY2017 vocational engines. Along with improvements in engine efficiency, manufacturers are likely to face a simultaneous challenge to achieve a significant reduction in tailpipe NOx emissions, as the ARB is expected to implement an ultra-low NOx emission standard in the 2024–27 timeframe. With this consideration, technology solutions for Phase-2 GHG will have to be NOx neutral or provide additional reduction in NOx emissions which is typically contrary to a reduction in fuel consumption.

In this study, various advanced engine technologies — such as engine downsizing and downspeeding, variable compression ratio, cylinder deactivation and turbocompounding — have been evaluated to improve engine efficiency with a goal to reach Phase-2 GHG engine requirements. Simultaneously, the impact of these technologies on engine-out NOx emission and aftertreatment inlet temperature has also been evaluated. The technologies were evaluated with a GT-Power model of a 7.7 liter medium HD diesel engine applied in vocational vehicles at steady-state operating conditions as well as over transient operating profiles. Significant fuel consumption reductions were observed with engine downsizing and engine downspeeding at the same engine-out NOx emissions as the baseline engine. Cylinder deactivation showed a moderate impact on fuel consumption while variable compression ratio and turbocompounding had a much lower impact on fuel consumption. In general, exhaust gas temperatures decreased with a reduction in fuel consumption, except in the case of cylinder deactivation where significant increase in exhaust gas temperatures was observed. The results of the study show that engine efficiency improvements beyond what has been mandated by the Phase-2 GHG regulations are possible without increasing the engine-out NOx emissions of a Phase-1 GHG compliant engine. However, if an ultra-low NOx emission standard is implemented as expected, some of the efficiency gains demonstrated in this study will need to be offset to achieve higher exhaust gas temperatures and lower engine-out NOx emissions.
An Alternative Calculation for Methane Number for Lean Burn Spark Ignited Engines Operating on Low Energy Content Gaseous Fuels
Authors: Xu Hui , zur Loye Axel O. , Bremmer Robin J.
Published: November 2017

Low energy content fuels such as landfill gas can contain a significant amount of diluents like CO2. Critical fuel properties including the lower heating value (LHV) and an anti-knock property, in particular the methane number (MN), should be considered to optimize operation of a spark ignited (SI) engine. The MN has been shown to be a good indicator of knock propensity in stoichiometric SI engines. However, this approach is not always as effective for lean burn SI engines. Two fuels with the same methane number, but with different compositions, may exhibit a different propensity to knocking in an advanced lean burn SI engine. This effect is particularly pronounced when comparing fuels that have different amounts of diluents. In this paper we propose an alternative calculation of the MN, which compensates for the effect of diluents. More specifically, we define a lean burn methane index (LBMI), which is calculated without the diluents. This approach was validated using chemical kinetics modeling. The analysis considered fundamental combustion properties, including laminar flame speed (LFS), adiabatic flame temperature (AFT) and the autoignition interval (AI). For this study, a baseline fuel was selected based on a typical US pipeline natural gas composition. CO2 was then added as a diluent to the baseline fuel to simulate low energy density fuel compositions. Lambda values were selected to provide the same AFT or engine-out NOx. Low energy content fuel were found to have very similar AI values (less than 2% relative difference) to the baseline fuel at the target lambda values. A key result of this study is that the LBMI is a much better predictor of knock propensity than the traditional MN, when comparing fuels with widely varying levels of dilution for advanced lean burn SI engines.
Model Based Design and Optimization for Large Bore Engines: Some Industrial Case Studies
Authors: Srinivasan Prashant , Bhat Sanketh , Sivasubramaniam Manthram , Methekar Ravi , Devarakonda Maruthi , Kumar Chandan
Published: November 2017

Large bore reciprocating internal combustion engines are used in a wide variety of applications such as power generation, transportation, gas compression, mechanical drives, and mining. Each application has its own unique requirements that influence the engine design & control strategy. The system architecture & control strategy play a key role in meeting the requirements. Traditionally, control design has come in at a later stage of the development process, when the system design is almost frozen. Furthermore, transient performance requirements have not always been considered adequately at early design stages for large engines, thus limiting achievable controller performance. With rapid advances in engine modeling capability, it has now become possible to accurately simulate engine behavior in steady-states and transients. In this paper, we propose an integrated model-based approach to system design & control of reciprocating engines and outline ideas, processes and real-world case studies for the same. Key benefits of this approach include optimized engine performance in terms of efficiency, transient response, emissions, system and cost optimization, tools to evaluate various concepts before engine build thus leading to significant reduction in development time & cost.
Effects of Fuel Quality on Gaseous Emissions From an 8.9L Spark-Ignited Natural Gas Engine Operated Over Prime-Mover Cycles for Unconventional Well Development
Authors: Johnson Derek , Besch Marc , Heltzel Robert , Jammalamadaka Sashank
Published: November 2017

Technology developments in directional drilling and hydraulic fracturing have led to increased natural gas reserves. Development of these unconventional resources is an energy intensive process. Prime-movers of unconventional well development were previously identified to be over-the-road trucks, drilling engines, and hydraulic stimulation engines. Diesel engines dominate these markets but industry is attempting to cut costs by using dual fuel and dedicated natural gas engines. On-road engines are subject to the transient FTP cycle for certification and off-road engines are subject to the 5-mode ISO 8178 D-2 cycle. It is well known that in-use activity can differ from certification activity. Significant in-use activity data for each prime-mover were collected and a Markov-Chain Monte-Carlo Simulation with a genetic algorithm was used to develop test cycles for each.

The developed test cycles allowed for operation of a smaller yet similar engine within a controlled laboratory environment. Laboratory tests utilized a Cummins 8.9L ISL-G to analyze the emissions of new cycles compared to certification cycles and to examine the effects of fuel quality on emissions. The ISL-G is a spark-ignited engine used for heavy-duty trucks and could see market penetration in fleets serving the well development industry. It is similar in technology to the Waukesha LI7044, which is used in drilling operations — both employ air fuel ratio control and three-way catalysts. For the case of “pump” quality fuel, compressed natural gas was used. The developed OTR truck cycle produced higher brake-specific emissions of CO2, CO, NOx, and lower HC emissions compared to the FTP. The drilling and fracturing cycles tended to have lower CO2 and HC emissions but higher CO emissions when compared to the D-2 cycle. Two additional fuel blends were used on the new cycles and represented blends with higher ethane and propane fractions — which are common to shale gases that could fuel prime-movers in the future. The minimum recommended methane number for this engine was 75 and additional fuel blends had methane numbers of 75.5 (propane blend) and 75.3 (ethane blend). As expected, CO2 emissions increased with increased alkane concentration, while opposite trends were shown for THC and CH4. NOx emissions also tended to decrease with higher ethane and propane blends, across all cycles. For all cycles and fuels, HC emissions were predominately CH4 - 94–97%. Variations in activity and the effects of different fuels should be addressed when estimating emissions since using standard certification or emissions factors may not be representative of in-use emissions.
Catalyst Ammonia Storage Measurements Using Radio Frequency Sensing
Authors: Aguilar Jonathan , Bromberg Leslie , Sappok Alexander , Ragaller Paul , Atehortua Jean , Liu Xiaojin
Published: November 2017

Motivated by increasingly strict NOx limits, engine manufactures have adopted selective catalytic reduction (SCR) technology to reduce engine-out NOx below mandated levels. In the SCR process, nitrogen oxides (NOx) react with ammonia (NH3) to form nitrogen and water vapor. The reaction is influenced by several variables, including stored ammonia on the catalyst, exhaust gas composition, and catalyst temperature. Currently, measurements from NOx and/or NH3 sensors upstream and downstream of the SCR are used with predictive models to estimate ammonia storage levels on the catalyst and control urea dosing.

This study investigated a radio frequency (RF) -based method to directly monitor the ammonia storage state of the SCR catalyst. This approach utilizes the SCR catalyst as a cavity resonator, in which an RF antenna excites electromagnetic waves within the cavity to monitor changes in the catalyst state. A mmonia storage causes changes in the dielectric properties of the catalyst, which directly impacts the RF signal. Changes in the RF signal relative to stored a mmonia (NH3) were evaluated over a wide frequency range as well as temperature and exhaust conditions. The RF response to NH3 storage, desorption, and oxidation on the SCR was observed to be well-correlated with changes in the catalyst state. Calibrated RF measurements demonstrate the ability to monitor the adsorption state of the SCR to within 10 % of the sensor full scale. The results indicate direct measurement of SCR ammonia storage levels, and resulting catalyst feedback control, via RF sensing to have significant potential for optimizing the SCR system to improve NOx conversion and decrease urea consumption.
Sources of Particulate Matter Emissions Variability From a Gasoline Direct Injection Engine
Authors: Ramos Manuel J. M. G. , Wallace James S.
Published: November 2017

Particulate matter (PM) emissions from gasoline direct injection (GDI) engines are a concern due to the health effects associated with ultrafine PM. This experimental study investigated sources of PM emissions measurement variability observed in previous tests and also examined the effect of ethanol content in gasoline on PM emissions. Some engine operating parameters (fuel and oil temperature, PCV filtration) and test conditions (dilution air conditions) were studied and controlled but could not account for the level of measurement variability observed. Fourier Transform Infrared Spectrometry (FTIR) measurements of gas phase hydrocarbon emissions provided evidence that changes in fuel composition were responsible for the variability. Exhaust emissions of toluene and ethanol were correlated positively with PM emissions, while emissions of isobutylene correlated negatively. Exhaust emissions of toluene and isobutylene were interpreted as markers of gasoline aromatic content and gasoline volatility respectively. Tests conducted with gasoline containing added toluene (10% v/v) supported this hypothesis and led to the overall conclusion that the PM emissions variability observed can be attributed to changes in the composition of the pump gasoline being used. Tests conducted with gasoline containing added ethanol (10% and 30% v/v) found that increasing ethanol fuel content increased PM emissions at the steady-state operating condition utilized.
CFD Modelling of Partial Fuel Stratification Combustion Using Detailed Fuel Surrogate Models and Tabulated Chemistry
Authors: Keum Seunghwan , Grover Ronald O. , Meijer Casper , Tap Ferry
Published: November 2017

With ever more stringent emissions and performance regulations, more emphasis and efforts have been made in accurate modeling of the combustion process and engine-out emissions in engine development. However, accurate modeling of the combustion process requires detailed chemistry. Highly detailed mechanisms typically include hundreds of species and thousands of reactions, and solution of such reaction set has been one of the largest bottlenecks in numerical modeling of the IC engine with CFD. Typically, the accuracy in chemistry modeling is sacrificed by reducing the mechanism size for the sake of computational efficiency. In this study, a lookup-table based approach is applied for modeling the combustion process in an HCCI engine. Instead of solving chemistry on-the-fly during the CFD simulations, the chemistry is solved for possible combination of thermodynamic and mixing conditions. The turbulence-chemistry interaction is considered using a flamelet approach. Then, the solution is stored in a table, such that chemistry information can be retrieved during the CFD simulation. The lookup-table method, referred to as Flamelet Generated Manifold (FGM), provides significant runtime reduction in CFD simulations with high fidelity chemistry modeling.

The FGM model was applied to a canonical HCCI experiment from Sandia National Laboratory. The experiment examined the effect of different levels of fuel stratification on ignition and combustion of a gasoline HCCI engine. The different levels of stratification were generated by controlling the amount of directly injected fuel. This case has been highly challenging for modeling using traditional modeling approaches. With FGM, it was possible to use the most detailed reaction mechanism to describe the chemistry as completely as one can. The effect of different surrogates on modeling results was investigated as well. It was found that the one proposed by Gauthier showed the most promising results in reproducing the highly complicated combustion with partial fuel stratification.
Cycle-to-Cycle Feedback for Combustion Control of Spark Advance at the Misfire Limit
Authors: Maldonado Bryan P. , Stefanopoulou Anna G.
Published: November 2017

At a given speed and load, the spark advance (SA) is tuned to reach the maximum break torque (MBT) timing to maximize efficiency. The use of exhaust gas recirculation (EGR) can further improve fuel economy at the same speed and load. As EGR increases, MBT moves towards a more advanced timing that can be limited by the high variability in the combustion process, reflected in unacceptable torque fluctuations. This variability is rapidly increased by the random occurrence of partial burns and/or misfires. In order to operate close to the misfire limit, a stochastic misfire controller has been designed to momentarily move from an undesired to an allowable misfire rate, without significantly increasing variability in the combustion process. Control-oriented models for the combustion process and misfire events are discussed. Simulation of the closed-loop system shows that the feedback misfire controller, on average, stays closer to the misfire limit than a more conventional controller designed to react when a misfire is detected.
A Numerical Investigation on NO2 Formation in a Natural Gas-Diesel Dual Fuel Engine
Authors: Li Yu , Li Hailin , Li Yongzhi , Yao Mingfa , Guo Hongsheng
Published: November 2017

The burning of natural gas (NG) in compression ignition dual fuel engines has been highlighted for its fuel flexibility, higher thermal efficiency and reduced particulate matter (PM) emissions. Recent research has reported the significant impact of the introduction of NG to the intake port on nitrogen dioxide (NO2) emissions, particularly at the low loads. However, the research on the mechanism of NO2 formation in dual fuel engines has not been reported.

This research simulates the formation and destruction of NO2 in a NG-diesel dual fuel engine using commercial CFD software CONVERGE coupled with a reduced primary reference fuel (PRF) mechanism consisting of 45 species and 142 reactions. The model was validated by comparing the simulated cylinder pressure, heat release rate, and nitrogen oxides (NOx) emissions with experimental data. The validated model was used to simulate the formation and destruction of NO2 in a NG-diesel dual fuel engine. The formation of NO2 and its correlation with the local concentration of nitric oxide (NO), methane, and temperature were examined and discussed. It was revealed that NO2 was mainly formed in the interface region between the hot NO-containing combustion products and the relatively cool unburnt methane-air mixture. NO2 formed at the early combustion stage is usually destructed to NO after the complete oxidation of methane and n-heptane, while NO2 formed during the post-combustion process would survive and exit the engine. This was supported by the distribution of NO and NO2 in the equivalence ratio (ER)-T diagram.

A detailed analysis of the chemical reactions occurring in the NO2 containing zone consisting of NO2, NO, O2, methane, etc., was conducted using a quasi-homogeneous constant volume model to identify the key reactions and species dominating NO2 formation and destruction. The HO2 produced during the post combustion process of methane was identified as the primary species dominating the formation of NO2. The simulation revealed the key reaction path for the formation of HO2 noted as CH4->CH3->CH2O->HCO->HO2, with conversion ratios of 98%, 74%, 90%, 98%, accordingly. The backward reaction of OH+NO2 = NO+HO2 consumed 34% of HO2 for the production of NO2.

It was concluded that the increased NO2 emissions from NG-diesel dual fuel engines was formed during the post combustion process due to higher concentration of HO2 produced during the oxidation process of the unburned methane at low temperature.
Relativity survives drop test
Authors: Cartlidge Edwin
Published: November 2017

Satellite tightens measurements of equivalence principle
Principles for gene drive research
Authors: Emerson Claudia , James Stephanie , Littler Katherine , Randazzo Filippo (Fil)
Published: November 2017

Sponsors and supporters of gene drive research respond to a National Academies
report
Savitzky–Golay smoothing and differentiation for polymerase chain reaction quantification
Authors: Gaudreault Charles , Salvas Joanny , Sirois Joël
Published: November 2017

In quantitative PCR (qPCR), replicates can minimize the impact of intra-assay variation; however, inter-assay variations must be minimized to obtain a robust quantification method. The method proposed in this study uses Savitzky–Golay smoothing and differentiation (SGSD) to identify a derivative-maximum-based cycle of quantification. It does not rely on curve modeling, as is the case with many existing techniques. PCR fluorescence data sets challenged for inter-assay variations (different thermocycler units, different reagents batches, different operators, different standard curves, and different labs) were used for the evaluation. The algorithm was compared with a four-parameter logistic model (4PLM) method, the Cy0 method, and the threshold method. The SGSD method compared favourably with all methods in terms of inter-assay variation. SGSD was statistically different from the 4PLM (P = 0.03), Cy0 (P = 0.05), and threshold (P = 0.004) methods on relative error comparison basis. For intra-assay variations, SGSD outperformed the threshold method (P = 0.005) and equalled the 4PLM and Cy0 methods (P > 0.05) on relative error basis. Our results demonstrate that the SGSD method could potentially be an alternative to sigmoid modeling based methods (4PLM and Cy0) when PCR data are challenged for inter-assay variations.
Demography of Sooty Fox Sparrows (Passerellaunalaschcensis) following a shift from a migratory to resident life history
Authors: Visty Hannah , Wilson Scott , Germain Ryan , Krippel Jessica , Arcese Peter
Published: November 2017

Identifying causes and consequences of variation in species life history has the potential to improve predictions about how climate and land-use change may affect the demography and distribution of species in future. Sooty Fox Sparrows (Passerella unalaschcensis (J.F. Gmelin, 1789); or commonly grouped within the Fox Sparrow, Passerella iliaca (Merrem, 1786)) were migrants that rarely bred in the Georgia Basin of British Columbia prior to ∼1950 but have since established resident populations. Data on 270 color-banded birds and 54 nests on Mandarte Island, British Columbia, allowed us to estimate demographic vital rates and population growth in one recently established population. Annual fecundity (F), estimated as the product of the number of broods initiated (1.5 ± 0.01; mean ± SD), clutch size (2.82 ± 0.44), and probability of survival to fledging (0.68 ± 0.02), exceeded values reported for migrants, supporting the hypothesis that residents invest more in reproduction, on average, than migrants within species. Estimating juvenile and adult overwinter survival (Sj= 0.32 ± 0.06 and Sa= 0.69 ± 0.05) next allowed us to simulate an expected distribution of population growth rates as λexp= Sa+ (Sj× F), given parameter error. Our estimate of λexp(1.61 ± 0.57) implies expeditious population growth, consistent with the species’ recent colonization of the region.
“An Be Jigi”: Collective cooking, whole grains, and technology transfer in Mali
Authors: Bauchspies Wenda K. , Diarra Fatimata , Rattunde Fred , Weltzien Eva
Published: November 2017

This paper addresses how available resources, food security, technology, and culture are shaping the choices rural Malian women are making to ensure the health, energy, and well-being of their families. This research contributed to evaluating an eight-year research project (An Be Jigi) targeting improved nutrition. The study, performed over four months, used semi-structured interviews of 120 women in six villages in Mali to assess the identified issues with qualitative and quantitative approaches. This paper describes the history of the An Be Jigi project, whole-grain processing techniques, and group cooking for knowledge sharing with rural women for improved nutrition. Interviews revealed substantial adoption of whole-grain processing techniques and women’s appreciation of the nutritional benefits of those techniques. The women engaged in group cooking ( cuisines collectives) appreciated the activities and mentioned multiple benefits from using them. Women identified access to mills, and to some extent the social stigma of laziness and poverty associated with whole-grain food, as limiting factors of adoption. This study of women’s practices and perceptions regarding use of whole grain tells a story of changing consumption habits being shaped by culture, technology, knowledge, and available resources. Malian women are agents of change and care in their adoption of new techniques and recipes for the improved nutrition of young children and households.
Chromosomal Thermal Index: a comprehensive way to integrate the thermal adaptation ofDrosophila subobscurawhole karyotype
Authors: Arenas Conxita , Zivanovic Goran , Mestres Francesc
Published: November 2017

Drosophila has demonstrated to be an excellent model to study the adaptation of organisms to global warming, with inversion chromosomal polymorphism having a key role in this adaptation. Here, we introduce a new index (Chromosomal Thermal Index or CTI) to quantify the thermal adaptation of a population according to its composition of “warm” and “cold” adapted inversions. This index is intuitive, has good statistical properties, and can be used to hypothesis on the effect of global warming on natural populations. We show the usefulness of CTI using data from European populations of D. subobscura, sampled in different years. Out of 15 comparisons over time, nine showed significant increase of CTI, in accordance with global warming expectations. Although large regions of the genome outside inversions contain thermal adaptation genes, our results show that the total amount of warm or cold inversions in populations seems to be directly involved in thermal adaptation, whereas the interactions between the inversions content of homologous and non-homologous chromosomes are not relevant.