bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser Polishing of Cold Work Steel AISI D2 for Dry Metal Forming Tools: Surface Homogenization, Refinement and Preparation for Self-Assembled Monolayers
Authors: Ross Ingo , Temmler André , Küpper Moritz , Prünte Stephan , Teller Marco , Schneider Jochen M. , Poprawe Reinhart
Published: April 2018

Liquid lubrication guarantees high precision and surface quality of workpieces in industrial forming processes. In the case of aluminum cold extrusion, wear and cold welding due to direct contact of tool and workpiece are usually prevented by the extensive use of lubricants. Since the use of lubricants is economically and ecologically unfavorable, surface treatments of tools by, e.g. laser polishing and/or coatings are in the focus of current investigations to substitute these lubricants and establish so called “dry metal forming” processes. The material AISI D2, a ledeburitic 12% chromium steel which is known to have a significant amount of chromium carbide precipitations, is widely used in cold extrusion for forming tools. The large fraction of chromium carbide precipitations, however, hinder the formation of a dense self-assembled monolayer (SAM) that is necessary to avoid direct contact of reactive aluminum with surface oxides of the tool. Therefore, a homogeneous distribution of the chemical elements with a smaller fraction or no chromium carbides in the steel matrix, particularly in the tool surface, is aimed for. Using laser polishing, the surface layer is molten by continuous or pulsed laser radiation. Within the melt pool, the elementary distribution is homogenized as a result of thermal convection and diffusion processes, as well as a smoothed surface and a grain refinement are achieved. Consequently, the effects of the surface treatment by laser polishing on the area coverage of self-assembled monolayers are investigated. Thus, a combined surface treatment by laser polishing and functionalization with a dense self-assembled monolayer shall reduce overall adhesive wear. For this investigation, several specimens of conventional manufactured and powder metallurgical molten AISI D2 are laser polished using continuous or pulsed laser radiation or a combination of both. The resulting surfaces are investigated by microscopy and spectroscopic techniques to analyze the surface topography and the elemental distribution near to the surface. These results are compared to those of conventionally hand-polished specimens. Furthermore, the influence of the element homogenization and grain refinement on the area coverage of self-assembled monolayers is explored. First results show that laser polishing of AISI D2 is suitable to achieve a reduction of grain size and a more homogeneous distribution of chromium carbides within the surface layer.
Effect of Contact Area on Friction Force in Sheet Metal Forming Operations
Authors: Mousavi Ali , Sperk Theresa , Gietzelt Tobias , Kunze Tim , Lasagni Andrés Fabián , Brosius Alexander
Published: April 2018

There are a number of ways to reduce friction such as lubrication, improving the surface roughness, reducing the acting surface pressure, surface texturing and reducing the contact area. In this study the effect of the contact size and surface pressure on process limits of a forming process is investigated. For this purpose draw-bending of U-Channel is subjected for testing of the effect of surface reduction by means of micro surface texturing and macro structuring. The results show that micro surface texturing and macro structuring of forming tools can reduce the friction force in forming processes. A combination of these approaches can be applied in tooling design to minimize the friction forces and ultimately realize a lubricant-free forming process.
Influence of Surface Texturing Sequence on Fatigue Life and Tribological Properties of Coated Tool Steel
Authors: Sedlaček Marko , Podgornik Bojan , Česnik Damir
Published: April 2018

The aim of this study was to investigate the influence of laser surface texturing on fatigue life and tribological properties. Textures were introduced before and after hard TiAlN coating deposition in order to investigate the sequence of surface texturing process. It was found that the sequence of surface texturing has an effect on tribological and fatigue life behaviour. If laser texturing is done after coating deposition, friction is lower because of the better wettability of steel in comparison with coating, but suffers in fatigue life properties.
KAM for gravity water waves in finite depth
Authors: Baldi Pietro , Berti Massimiliano , Haus Emanuele , Montalto Riccardo
Published: April 2018

We present the recent result in [3] concerning the existence of Cantor families of small amplitude, linearly stable, time
quasi-periodic
standing water wave solutions – i.e. periodic and even in the space variable

x

– of a bi-dimensional ocean with finite depth under the action of pure gravity. Such a result holds for all the values of the depth parameter in a Borel set of asymptotically full measure.
Pointwise estimates for solutions of semilinear parabolic inequalities with a potential
Authors: Montoro Luigi , Punzo Fabio , Sciunzi Berardino
Published: April 2018

We obtain pointwise estimates for solutions of semilinear parabolic equations with a potential on connected domains both of

\mathbb R^n

and of general Riemannian manifolds. Our results generalize to the parabolic case those shown in [10] for elliptic equations.
Elementary solution of an infinite sequence of instances of the Hurwitz problem
Authors: Ferragut Tom , Petronio Carlo
Published: April 2018

We prove that there exists no branched cover from the torus to the sphere with degree 3h and 3 branching points in the target with local degrees (3, … , 3), (3, … , 3), (4, 2, 3, … , 3) at their preimages. The result was already established by Izmestiev, Kusner, Rote, Springborn, and Sullivan, using geometric techniques, and by Corvaja and Zannier with a more algebraic approach, whereas our proof is topological and completely elementary: besides the definitions, it only uses the fact that on the torus a simple closed curve can only be trivial (in homology, or equivalently bounding a disc, or equivalently separating) or non-trivial.
On the Moser–Trudinger inequality in fractional Sobolev–Slobodeckij spaces
Authors: Parini Enea , Ruf Bernhard
Published: April 2018

We give a contribution to the problem of finding the optimal exponent in the Moser–Trudinger inequality in the fractional Sobolev–Slobodeckij space

\widetilde{W}^{s,p}_0(\Omega)

, where

\Omega \subset \mathbb R^N

is a bounded domain,

s \in (0,1)

, and

sp = N

. We exhibit an explicit exponent

\alpha^*_{s,N}>0

, which does not depend on

\Omega

, such that the Moser–Trudinger inequality does not hold true for

\alpha \in (\alpha^*_{s,N},+\infty)

.
Simple Frameworks for Daily Work: Innovative Strategies to Coach Residents Struggling With Time Management, Organization, and Efficiency
Authors: DeKosky Allison S. , Sedrak Mina S. , Goren Eric , Dine C. Jessica , Warburton Karen M.
Published: April 2018

Background 

Organization and efficiency are central to success on busy inpatient services and may be relevant to demonstrating certain milestones. Most residents adopt these skills by observing supervisors and peers. For some, this method of emulation and adaptation does not occur, with the potential for a negative effect on patient care and team morale. Information on effective strategies for remediating organization and efficiency deficits is lacking.

Objective 

We explored the major themes of organization and efficiency referred to the University of Pennsylvania Department of Medicine Early Intervention and Remediation Committee (EIRC), and developed tools for their remediation.

Methods 

Assessments of residents and fellows referred to the EIRC between July 2014 and October 2016 were reviewed for organization and efficiency deficits. Common areas were identified, and an iterative process of learner observations and expert input was used to develop remediation tools.

Results 

Over a 2-year period, the EIRC developed remediation plans for 4% of residents (13 of 342 total residents), and for 1 internal medicine subspecialty fellow. Organization and efficiency was the primary or secondary deficit in more than half of those assessed. Most common deficiencies involved admitting a patient efficiently, performing effective prerounding, and composing daily progress notes/presentations. Remediation tools that provided deconstruction of tasks to their most granular and reproducible components were effective in improving performance.

Conclusions 

Deficits in organization and efficiency can disproportionately affect resident performance and delay milestone achievement. Many residents would benefit from detailed frameworks and assistance with new approaches to basic elements of daily work.
Experiential Communications Curriculum to Improve Resident Preparedness When Responding to Discriminatory Comments in the Workplace
Authors: March Christine , Walker Lorne W. , Toto Regina L. , Choi Sylvia , Reis Evelyn C. , Dewar Stephanie
Published: April 2018

Background 

Patients and families can make discriminatory comments leading to physician distress. Residents receive little training in appropriate responses to such comments and may be ill equipped to respond to intolerance without alienating the individual(s) making the comments.

Objective 

We assessed whether a simulated curriculum would enhance pediatrics residents' ability to effectively respond to discriminatory comments.

Methods 

In the 2016–2017 academic year, we modified an existing communication skills curriculum for senior pediatrics residents. Residents engaged a simulated parent who used discriminatory speech in 4 scenarios, followed by a group debriefing. We conducted anonymous surveys to assess residents' preparedness to respond to these comments before and immediately following participation and examined their experience with discriminatory comments in the workplace.

Results 

The majority of residents reported prior experience with discriminatory comments (32 of 45 [71%] witnessed such comments, and 27 of 48 [56%] were targeted by such comments), most often regarding age, race, and ethnicity. Mean precourse scores ranged from 2.1 to 3.1 (on a 5-point scale) regarding ability to engage in a firm yet respectful dialogue, to reference the hospital code of conduct, to coach a learner to respond, and to facilitate a team debrief. Mean postcourse scores improved significantly for these questions (range 3.8–4.1). The greatest improvement was in referencing the code of conduct (2.1 versus 4.0, P < .001).

Conclusions 

Immediately after participating in simulation, pediatrics residents reported a significant improvement in self-reported readiness to respond to discriminatory comments made by a parent and reported the simulation experience was beneficial.
Linking Destination Brand Personality, Self-congruity and Tourist Behaviour: A Local Spa resort case study
Authors: Rutelione Ausra , Hopenienė Rimantė , Žalimienė Kristina
Published: April 2018

This study was designed to explore the relationship between destination brand personality, self-congruity and the behavioral intentions of tourists at a local spa resort. The findings indicate that domestic tourists (N=232) of the spa resort attribute personal characteristics to the destination, and the brand personality of this resort is a combination of five dimensions which positively correlate with the tourists’ intentions to return to and recommend the location. The results of the study also confirm that the self-congruity theory can be applied to a spa destination, as positive relationships between all four self-congruity dimensions and intentions to recommend were found. However, our research reveals that there is negative though insignificant correlation between social self-congruity and intention to return.
Wavelet Transform Modulus Maxima and Holder Exponents Combined with Transient Detection for the Differentiation of Pitting Corrosion Using Electrochemical Noise
Authors: Homborg A.M. , Oonincx P.J. , Mol J.M.C.
Published: April 2018

A potentially powerful tool to detect and classify corrosion mechanisms is the analysis of electrochemical noise (EN). Data analysis in the time-frequency domain using, e.g., continuous wavelet transform (CWT) allows the extraction of localized frequency information, providing information on the type of corrosion, i.e., uniform or localized corrosion, from the EN signal. The CWT provides the opportunity to analyze changes in frequency behavior of EN signals over time. In the presence of transients generated by pitting corrosion that occur only during short instants of time, this is an important property. This paper introduces the combination of automated transient detection with wavelet transform modulus maxima (WTMM) and the Holder exponent. WTMM enhances the determination of transient frequencies by indicating the ridges of a CWT spectrum. The Holder exponent, a measure of singularity of an EN signal, provides a single parameter discrimination tool based on WTMM and serves to differentiate between general corrosion and two types of pitting corrosion of stainless steel Type 304 exposed to aqueous HCl solutions of different concentrations and as such at different pH values.
Organic aerosol in the summertime southeastern United States: components and their link to volatility distribution, oxidation state and hygroscopicity
Authors: Kostenidou Evangelia , Karnezi Eleni , Hite Jr. James R. , Bougiatioti Aikaterini , Cerully Kate , Xu Lu , Ng Nga L. , Nenes Athanasios , Pandis Spyros N.
Published: April 2018

Abstract. The volatility distribution of the
organic aerosol (OA) and its sources during the Southern Oxidant and Aerosol
Study (SOAS; Centreville, Alabama) was constrained using measurements from an
Aerodyne high-resolution time-of-flight aerosol mass spectrometer
(HR-ToF-AMS) and a thermodenuder (TD). Positive matrix factorization (PMF)
analysis was applied on both the ambient and thermodenuded high-resolution
mass spectra, leading to four factors: more oxidized oxygenated OA (MO-OOA),
less oxidized oxygenated OA (LO-OOA), an isoprene epoxydiol (IEPOX)-related
factor (isoprene-OA) and biomass burning OA (BBOA). BBOA had the highest mass
fraction remaining (MFR) at 100 ∘C, followed by the isoprene-OA, and
the LO-OOA. Surprisingly the MO-OOA evaporated the most in the TD. The
estimated effective vaporization enthalpies assuming an evaporation
coefficient equal to unity were 58 ± 13 kJ mol−1 for the LO-OOA,
89 ± 10 kJ mol−1 for the MO-OOA, 55 ± 11 kJ mol−1
for the BBOA, and 63 ± 15 kJ mol−1 for the isoprene-OA. The
estimated volatility distribution of all factors covered a wide range
including both semi-volatile and low-volatility components. BBOA had the
lowest average volatility of all factors, even though it had the lowest
O : C ratio among all factors. LO-OOA was the more volatile factor and
its high MFR was due to its low enthalpy of vaporization according to the
model. The isoprene-OA factor had intermediate volatility, quite higher than
suggested by a few other studies. The analysis suggests that deducing the
volatility of a factor only from its MFR could lead to erroneous conclusions.
The oxygen content of the factors can be combined with their estimated
volatility and hygroscopicity to provide a better view of their physical
properties.
Aerosol midlatitude cyclone indirect effects in observations and high-resolution simulations
Authors: McCoy Daniel T. , Field Paul R. , Schmidt Anja , Grosvenor Daniel P. , Bender Frida A.-M. , Shipway Ben J. , Hill Adrian A. , Wilkinson Jonathan M. , Elsaesser Gregory S.
Published: April 2018

Abstract. Aerosol–cloud interactions are a major source of uncertainty in inferring the
climate sensitivity from the observational record of temperature. The
adjustment of clouds to aerosol is a poorly constrained aspect of these
aerosol–cloud interactions. Here, we examine the response of midlatitude
cyclone cloud properties to a change in cloud droplet number concentration
(CDNC). Idealized experiments in high-resolution, convection-permitting
global aquaplanet simulations with constant CDNC are compared to 13
years of remote-sensing observations. Observations and idealized aquaplanet
simulations agree that increased warm conveyor belt (WCB) moisture flux into
cyclones is consistent with higher cyclone liquid water path (CLWP). When
CDNC is increased a larger LWP is needed to give the same rain rate. The LWP
adjusts to allow the rain rate to be equal to the moisture flux into the
cyclone along the WCB. This results in an increased CLWP for
higher CDNC at a fixed WCB moisture flux in both observations and
simulations. If observed cyclones in the top and bottom tercile of CDNC are
contrasted it is found that they have not only higher CLWP but also cloud
cover and albedo. The difference in cyclone albedo between the cyclones in
the top and bottom third of CDNC is observed by CERES to be between 0.018 and
0.032, which is consistent with a 4.6–8.3 Wm−2 in-cyclone enhancement
in upwelling shortwave when scaled by annual-mean insolation. Based on a
regression model to observed cyclone properties, roughly 60 % of the
observed variability in CLWP can be explained by CDNC and WCB moisture flux.
Study of the daily and seasonal atmospheric CH4 mixing ratio variability in a rural Spanish region using 222Rn tracer
Authors: Grossi Claudia , Vogel Felix R. , Curcoll Roger , Àgueda Alba , Vargas Arturo , Rodó Xavier , Morguí Josep-Anton
Published: April 2018

Abstract. The ClimaDat station at Gredos (GIC3) has been continuously measuring atmospheric (dry air) mixing ratios of carbon dioxide (CO2) and methane (CH4), as well as meteorological parameters, since November 2012. In this study we investigate the atmospheric variability of CH4 mixing ratios between 2013 and 2015 at GIC3 with the help of co-located observations of 222Rn concentrations, modelled 222Rn fluxes and modelled planetary boundary layer heights (PBLHs). Both daily and seasonal changes in atmospheric CH4 can be better understood with the help of atmospheric concentrations of 222Rn (and the corresponding fluxes). On a daily timescale, the variation in the PBLH is the main driver for 222Rn and CH4 variability while, on monthly timescales, their atmospheric variability seems to depend on emission changes. To understand (changing) CH4 emissions, nocturnal fluxes of CH4 were estimated using two methods: the radon tracer method (RTM) and a method based on the EDGARv4.2 bottom-up emission inventory, both using FLEXPARTv9.0.2 footprints. The mean value of RTM-based methane fluxes (FR_CH4) is 0.11 mg CH4 m−2 h−1 with a standard deviation of 0.09 or 0.29 mg CH4 m−2 h−1 with a standard deviation of 0.23 mg CH4 m−2 h−1 when using a rescaled 222Rn map (FR_CH4_rescale). For our observational period, the mean value of methane fluxes based on the bottom-up inventory (FE_CH4) is 0.33 mg CH4 m−2 h−1 with a standard deviation of 0.08 mg CH4 m−2 h−1. Monthly CH4 fluxes based on RTM (both FR_CH4 and FR_CH4_rescale) show a seasonality which is not observed for monthly FE_CH4 fluxes. During January–May, RTM-based CH4 fluxes present mean values 25 % lower than during June–December. This seasonal increase in methane fluxes calculated by RTM for the GIC3 area appears to coincide with the arrival of transhumant livestock at GIC3 in the second half of the year.
Global evaluation and calibration of a passive air sampler for gaseous mercury
Authors: McLagan David S. , Mitchell Carl P. J. , Steffen Alexandra , Hung Hayley , Shin Cecilia , Stupple Geoff W. , Olson Mark L. , Luke Winston T. , Kelley Paul , Howard Dean , Edwards Grant C. , Nelson Peter F. , Xiao Hang , Sheu Guey-Rong , Dreyer Annekatrin , Huang Haiyong , Abdul Hussain Batual , Lei Ying D. , Tavshunsky Ilana , Wania Frank
Published: April 2018

Abstract. Passive air samplers (PASs) for gaseous mercury
(Hg) were deployed for time periods between 1 month and 1 year at 20 sites
across the globe with continuous atmospheric Hg monitoring using active
Tekran instruments. The purpose was to evaluate the accuracy of the PAS
vis-à-vis the industry standard active instruments and to determine a
sampling rate (SR; the volume of air stripped of gaseous Hg per unit of time)
that is applicable across a wide range of conditions. The sites spanned a
wide range of latitudes, altitudes, meteorological conditions, and gaseous
Hg concentrations. Precision, based on 378 replicated deployments performed
by numerous personnel at multiple sites, is 3.6 ± 3.0 %1, confirming the PAS's excellent reproducibility
and ease of use. Using a SR previously determined at a single site, gaseous Hg
concentrations derived from the globally distributed PASs deviate from
Tekran-based concentrations by 14.2 ± 10 %. A recalibration
using the entire new data set yields a slightly higher SR of 0.1354 ± 0.016 m3 day−1. When concentrations are derived from the PAS using this revised SR the difference between concentrations from active and passive sampling is reduced to 8.8 ± 7.5 %. At the mean gaseous Hg concentration across the study sites
of 1.54 ng m−3, this represents an ability to resolve concentrations to
within 0.13 ng m−3. Adjusting the sampling rate to deployment
specific temperatures and wind speeds does not decrease the difference in
active–passive concentration further (8.7 ± 5.7 %), but
reduces its variability by leading to better agreement in Hg concentrations
measured at sites with very high and very low temperatures and very high
wind speeds. This value (8.7 ± 5.7 %) represents a
conservative assessment of the overall uncertainty of the PAS due to
inherent uncertainties of the Tekran instruments. Going forward, the
recalibrated SR adjusted for temperature and wind speed should be used,
especially if conditions are highly variable or deviate considerably from
the average of the deployments in this study (9.89 ∘C,
3.41 m s−1). Overall, the study demonstrates that the sampler is
capable of recording background gaseous Hg concentrations across a wide
range of environmental conditions with accuracy similar to that of industry
standard active sampling instruments. Results at sites with active
speciation units were inconclusive on whether the PASs take up total gaseous
Hg or solely gaseous elemental Hg primarily because gaseous oxidized Hg
concentrations were in a similar range as the uncertainty of the PAS.
Modeling organic aerosol concentrations and properties during
winter 2014 in the northwestern Mediterranean region
Authors: Chrit Mounir , Sartelet Karine , Sciare Jean , Majdi Marwa , Nicolas José , Petit Jean-Eudes , Dulac François
Published: April 2018

Abstract. Organic aerosols are measured at a remote site (Ersa) on Corsica Cape in the northwestern Mediterranean basin during the Chemistry-Aerosol Mediterranean Experiment (CharMEx) winter campaign of 2014, when high organic concentrations from anthropogenic origin are observed. This work aims at representing the observed organic aerosol concentrations and properties (oxidation state) using the air-quality model Polyphemus with a surrogate approach for secondary organic aerosol (SOA) formation. Because intermediate/semi-volatile organic compounds (I/S-VOC) are the main precursors of SOA at Ersa during the winter 2014, different parameterizations to represent the emission and ageing of I/S-VOC were implemented in the chemistry-transport model of the air-quality platform Polyphemus (different volatility distribution emissions, single-step oxidation vs multi-step oxidation within a Volatility Basis Set framework, inclusion of non-traditional volatile organic compounds NTVOC). Simulations using the different parameterizations are compared to each other and to the measurements (concentration and oxidation state). The high observed organic concentrations are well reproduced whatever the parameterizations. They are slightly under-estimated with most parameterizations, but they are slightly over-estimated when the ageing of NTVOC is taken into account. The volatility distribution at emissions influences more strongly the concentrations than the choice of the parameterization that may be used for ageing (single-step oxidation vs multi-step oxidation), stressing the importance of an accurate characterization of emissions. Assuming the volatility distribution of sectors other than residential heating to be the same as residential heating may lead to a strong under-estimation of organic concentrations. The observed organic oxidation and oxygenation states are strongly under-estimated in all simulations, even when a recently developed parameterization for modeling the ageing of I/S-VOC from residential heating is used. This suggests that uncertainties in the ageing of I/S-VOC emissions remain to be elucidated, with a potential role of organic nitrate from anthropogenic precursors and highly oxygenated organic molecules.
Photochemical box-modelling of volcanic SO2 oxidation: isotopic constraints
Authors: Galeazzo Tommaso , Bekki Slimane , Martin Erwan , Savarino Joël , Arnold Stephen R.
Published: April 2018

Abstract. The photochemical box-model CiTTyCAT is used to analyse the absence of oxygen mass-independent anomalies (O-MIF) in volcanic sulphates produced in the troposphere. An aqueous sulphur oxidation module is implemented in the model and coupled to an oxygen isotopic scheme describing the transfer of O-MIF during the oxidation of SO2 by OH in the gas-phase, and by H2O2, O3 and O2 catalysed by TMI in the liquid phase. Multiple model simulations are performed in order to explore the relative importance of the various oxidation pathways for a range of plausible conditions in volcanic plumes. Note that the chemical conditions prevailing in dense volcanic plumes are radically different from those prevailing in the surrounding background air. The first salient finding is that, according to model calculations, OH is expected to carry a very significant O-MIF in sulphur-rich volcanic plumes and, hence, that the volcanic sulphate produced in the gas phase would have a very significant positive isotopic enrichment. The second finding is that, although H2O2 is a major oxidant of SO2 throughout the troposphere, it is very rapidly consumed in sulphur-rich volcanic plumes. As a result, H2O2 is found to be a minor oxidant for volcanic SO2. According to the simulations, oxidation of SO2 by O3 is negligible because volcanic aqueous phases are too acidic. The model predictions of minor or negligible sulphur oxidation by H2O2 and O3, two oxidants carrying large O-MIF, are consistent with the absence of O-MIF seen in most isotopic measurements of volcanic tropospheric sulphate. The third finding is that oxidation by O2/TMI in volcanic plumes could be very substantial and, in some cases, dominant, notably because the rates of SO2 oxidation by OH, H2O2, and O3 are vastly reduced in a volcanic plume compared to the background air. Only cases where sulphur oxidation by O2/TMI is very dominant can explain the isotopic composition of volcanic tropospheric sulphate.
Analysis of ionospheric structure influences on residual ionospheric errors in GNSS radio occultation bending angles based on ray tracing simulations
Authors: Liu Congliang , Kirchengast Gottfried , Sun Yueqiang , Zhang Kefei , Norman Robert , Schwaerz Marc , Bai Weihua , Du Qifei , Li Ying
Published: April 2018

Abstract. The Global Navigation Satellite System (GNSS) radio occultation (RO)
technique is widely used to observe the atmosphere for applications such as
numerical weather prediction and global climate monitoring. The ionosphere is
a major error source to RO at upper stratospheric altitudes, and a linear
dual-frequency bending angle correction is commonly used to remove the
first-order ionospheric effect. However, the higher-order residual
ionospheric error (RIE) can still be significant, so it needs to be
further mitigated for high-accuracy applications, especially from 35 km
altitude upward, where the RIE is most relevant compared to the decreasing
magnitude of the atmospheric bending angle. In a previous study we quantified
RIEs using an ensemble of about 700 quasi-realistic end-to-end simulated RO
events, finding typical RIEs at the 0.1 to 0.5 µrad noise level, but
were left with 26 exceptional events with anomalous RIEs at the 1 to 10 µrad level that remained unexplained. In this study, we focused on
investigating the causes of the high RIE of these exceptional events,
employing detailed along-ray-path analyses of atmospheric and ionospheric
refractivities, impact parameter changes, and bending angles and RIEs under
asymmetric and symmetric ionospheric structures. We found that the main
causes of the high RIEs are a combination of physics-based effects – where
asymmetric ionospheric conditions play the primary role, more than the
ionization level driven by solar activity – and technical ray tracer effects
due to occasions of imperfect smoothness in ionospheric refractivity model
derivatives. We also found that along-ray impact parameter variations of more
than 10 to 20 m are possible due to ionospheric asymmetries and,
depending on prevailing horizontal refractivity gradients, are positive or
negative relative to the initial impact parameter at the GNSS transmitter.
Furthermore, mesospheric RIEs are found generally higher than
upper-stratospheric ones, likely due to being closer in tangent point heights to
the ionospheric E layer peaking near 105 km, which increases RIE
vulnerability. In the future we will further improve the along-ray modeling
system to fully isolate technical from physics-based effects and to use it
beyond this work for additional GNSS RO signal propagation studies.
Considerations for temperature sensor placement on rotary-wing
unmanned aircraft systems
Authors: Greene Brian R. , Segales Antonio R. , Waugh Sean , Duthoit Simon , Chilson Phillip B.
Published: April 2018

Abstract. With their recent surge in commercial accessibility, rotary-wing unmanned aircraft systems (rwUAS) are proving to be a viable method of atmospheric sensing and sampling while improving upon the shortcomings of traditional methods. To maximize the potential for these platforms to provide reliable observations, it is imperative to have an understanding of their strengths and limitations under varying environmental conditions. This study focuses on the quality of measurements relative to sensor locations on board rwUAS. Typically, thermistors require aspiration and proper siting free of heat sources to make representative measurements of the atmosphere. In an effort to characterize ideal locations for sensor placement, a series of experiments were conducted in the homogeneous environment of an indoor chamber with a pedestal-mounted rwUAS. A suite of thermistors along with a wind probe were mounted inside of a solar shield, which was affixed to a linear actuator arm. The actuator arm was configured such that the sensors within the solar shield would travel underneath the platform into and out of the propeller wash. The actuator arm was displaced horizontally underneath the platform while the motors were throttled to 50 percent, yielding a time series of temperature and wind speed which could be compared to temperatures being collected in the ambient environment. Results indicate that temperatures may be biased on the order of 0.5–1.0 °C and vary appreciably without aspiration, sensors placed close to the tips of the rotors may experience biases due to frictional and compressional heating as a result of turbulent fluctuations, and sensors in proximity to motors may experience biases approaching 1 °C. From these trials, it has been determined that sensor placement underneath a propeller on an rwUAS a distance of one quarter the length of the propeller from the tip is most likely to be minimally impacted from influences of turbulence and motor, compressional, and frictional heating while still maintaining adequate airflow. When opting to use rotor wash as a means for sensor aspiration, the user must be cognizant of these potential sources of platform-induced heating when determining sensor location.
Climatology of GPS signal loss observed by Swarm satellites
Authors: Xiong Chao , Stolle Claudia , Park Jaeheung
Published: April 2018

Abstract. By using 3-year global positioning system (GPS) measurements from
December 2013 to November 2016, we provide in this study a detailed survey on
the climatology of the GPS signal loss of Swarm onboard receivers. Our
results show that the GPS signal losses prefer to occur at both low latitudes
between ±5 and ±20∘ magnetic latitude (MLAT) and high
latitudes above 60∘ MLAT in both hemispheres. These events at all
latitudes are observed mainly during equinoxes and December solstice months,
while totally absent during June solstice months. At low latitudes the GPS
signal losses are caused by the equatorial plasma irregularities shortly
after sunset, and at high latitude they are also highly related to the large
density gradients associated with ionospheric irregularities. Additionally,
the high-latitude events are more often observed in the Southern Hemisphere,
occurring mainly at the cusp region and along nightside auroral latitudes.
The signal losses mainly happen for those GPS rays with elevation angles less
than 20∘, and more commonly occur when the line of sight between GPS
and Swarm satellites is aligned with the shell structure of plasma
irregularities. Our results also confirm that the capability of the Swarm
receiver has been improved after the bandwidth of the phase-locked loop (PLL)
widened, but the updates cannot radically avoid the interruption in tracking
GPS satellites caused by the ionospheric plasma irregularities. Additionally,
after the PLL bandwidth increased larger than 0.5 Hz, some unexpected
signal losses are observed even at middle latitudes, which are not related to
the ionospheric plasma irregularities. Our results suggest that rather than
1.0 Hz, a PLL bandwidth of 0.5 Hz is a more suitable value
for the Swarm receiver. Keywords. Ionosphere (equatorial ionosphere; ionospheric irregularities) – radio science (radio wave propagation)
Phylogeny of the Stipa and implications for grassland evolution in China: based on biogeographic evidence
Authors: Zhang Qing , Chen Junjun , Ding Yong
Published: April 2018

Abstract. The evolution of Chinese grassland is a still an important question biogeography. In this study, the phylogeny of 20 Stipa species (extensively distributed in Chinese grassland) was established to explore the origin and dispersal routes of Chinese grassland. It showed that Stipa species originated at 28 MaBP and they started to differentiate in central Inner Mongolia at 22 MaBP. Then, Stipa species expanded along four routes: (1) they expanded from central Mongolia to the Qilian Mountains, Qinghai, and western Tibet at 16 MaBP. They then gradually expanded from western to eastern Tibet from 11–6 MaBP. (2) At 12 MaBP, they expanded from central Inner Mongolia to the Helan Mountains. (3) At 8 MaBP, they expanded from central Inner Mongolia to the Xinjiang area. (4) At 4 MaBP, they expanded from central to eastern Inner Mongolia. Therefore, we could deduce the formation order of Chinese grasslands: central Inner Mongolia > Qilian Mountains > Qinghai > western Tibet > Helan Mountains > Xinjiang > central Tibet > eastern Tibet > eastern Inner Mongolia. We highlight the importance of the uplift of the Qinghai-Tibet Plateau and paleoclimate changes in triggering the origin and evolution of Stipa species and Chinese grasslands.
Distribution of Fe isotopes in particles and colloids in the salinity
gradient along the Lena River plume, Laptev Sea
Authors: Conrad Sarah , Ingri Johan , Gelting Johan , Nordblad Fredrik , Engström Emma , Rodushkin Ilia , Andersson Per S. , Porcelli Don , Gustafsson Örjan , Semiletov Igor , Öhlander Björn
Published: April 2018

Abstract. Riverine Fe input is the primary Fe source to the ocean. This study is focused on the distribution of Fe along the Lena River freshwater plume in the Laptev Sea using samples from a 600 km long transect in front of the Lena River mouth. Separation of the particulate (> 0.22 µm), colloidal (0.22 µm–1 kDa), and truly dissolved ( 99 % of particulate Fe and about 90 % of the colloidal Fe was observed across the shelf, while the truly dissolved phase was almost constant across the Laptev Sea. Thus, the truly dissolved Fe could be an important source of bioavailable Fe for plankton in the central Arctic Ocean, together with the colloidal Fe. Fe-isotope analysis showed that the particulate phase and the sediment below the Lena River freshwater plume had negative δ56Fe values (relative to IRMM-14). The colloidal Fe phase showed negative δ56Fe values close to the river mouth (about −0.20 ‰) and positive δ56Fe values in the outermost stations (about +0.10 ‰). We suggest that the shelf zone acts as a sink for Fe particles and colloids with negative δ56Fe values, representing chemically reactive ferrihydrites. While the positive δ56Fe values of the colloidal phase within the outer Lena River freshwater plume, might represent Fe-oxyhydroxides, which remain in the water column, and will be the predominant δ56Fe composition in the Arctic Ocean.
Predominance of methanogens over methanotrophs contributes to high methane emissions in rewetted fens
Authors: Wen Xi , Unger Viktoria , Jurasinski Gerald , Koebsch Franziska , Horn Fabian , Rehder Gregor , Sachs Torsten , Zak Dominik , Lischeid Gunnar , Knorr Klaus-Holger , Böttcher Michael , Winkel Matthias , Liebner Susanne
Published: April 2018

Abstract. The rewetting of drained peatlands alters peat geochemistry and often leads to sustained elevated methane emission. Although this methane is produced entirely by microbial activity, the distribution and abundance of methane-cycling microbes in rewetted peatlands, especially in fens, is rarely described. In this study, we compare the community composition and abundance of methane-cycling microbes in relation to peat porewater geochemistry in two rewetted fens in northeastern Germany, a coastal brackish fen and a freshwater riparian fen, with known high methane fluxes. We utilized 16S rDNA high-throughput sequencing and quantitative polymerase chain reaction on 16S rDNA, mcrA, and pmoA genes to determine microbial community composition and the abundance of total bacteria, methanogens, and methanotrophs. Electrical conductivity was more than three times higher in the coastal fen than in the riparian fen, averaging 5.3 and 1.5 mS cm−1, respectively. Porewater concentrations of terminal electron acceptors varied within and among the fens. This was also reflected in similarly high intra- and inter-site variations of microbial community composition. Despite these differences in environmental conditions and electron acceptor availability, we found a low abundance of methanotrophs and a high abundance of methanogens, represented in particular by Methanosaetaceae, in both fens. This suggests that rapid re/establishment of methanogens and slow re/establishment of methanotrophs contributes to prolonged increased methane emissions following rewetting.
High variability of export fluxes along the North Atlantic GEOTRACES section GA01: Particulate organic carbon export deduced from the 234Th method
Authors: Lemaitre Nolwenn , Planchon Frédéric , Planquette Hélène , Dehairs Frank , Fonseca-Batista Debany , Roukaerts Arnout , Deman Florian , Tang Yi , Mariez Clarisse , Sarthou Géraldine
Published: April 2018

Abstract. In this study, we report Particulate Organic Carbon (POC) export fluxes estimated using the 234Th-based approach in different biogeochemical basins of the North Atlantic, as part of the GEOTRACES GA01 expedition (GEOVIDE, May–June 2014). Surface POC export fluxes were deduced by combining export fluxes of 234Th with the POC to 234Th ratio of sinking particles at the depth of export. Particles were collected in two size classes (> 53 µm and 1–53 µm) using in-situ pumps and the large size fraction was considered as representative of sinking material. Surface POC export fluxes revealed latitudinal variations between provinces ranging from 1.4 mmol C m−2 d−1 in the Irminger basin where the bloom was close to its maximum peak, to 12 mmol C m−2 d−1 near the Iberian Margin where the bloom had already declined. In addition to the bloom staging, the variations of POC export fluxes were also related to the phytoplankton community structure. In line with previous studies, the presence of coccolithophorids and diatoms appeared to increase the POC export flux while stations dominated by pico-phytoplankton cells, such as cyanobacteria, were characterized by lower fluxes. The surface POC export fluxes were then compared to in-situ and satellite primary production (PP) in order to assess the export efficiency. This ratio strongly varied regionally and was generally low (≤ 14 %), except at two stations located near the Iberian margin (35 %) and within the Labrador basin (38 %), which were characterized by unusual low in-situ PP. We thus conclude that the North Atlantic during this period was not as efficient in exporting carbon from the surface, as described in recent studies. Finally, we estimated the flux of POC exported 100 m below the surface export depth in order to investigate the transfer efficiency along the section. This parameter was also highly regional-dependent but the lowest attenuation of the POC flux was observed at stations where coccolithophorids dominated.
High-resolution observations in the western Mediterranean Sea: the REP14-MED experiment
Authors: Onken Reiner , Fiekas Heinz-Volker , Beguery Laurent , Borrione Ines , Funk Andreas , Hemming Michael , Hernandez-Lasheras Jaime , Heywood Karen J. , Kaiser Jan , Knoll Michaela , Mourre Baptiste , Oddo Paolo , Poulain Pierre-Marie , Queste Bastien Y. , Russo Aniello , Shitashima Kiminori , Siderius Martin , Thorp Küsel Elizabeth
Published: April 2018

Abstract. The observational part of the REP14-MED experiment was conducted in June 2014 in the Sardo-Balearic Basin west of Sardinia (western Mediterranean Sea). Two research vessels collected high-resolution oceanographic data by means of hydrographic casts, towed systems, and underway measurements. In addition, a vast amount of data was provided by a fleet of 11 ocean gliders, time series were available from moored instruments, and information on Lagrangian flow patterns was obtained from surface drifters and one profiling float. The spatial resolution of the observations encompasses a spectrum over 4 orders of magnitude from 𝒪(101 m) to 𝒪(105 m), and the time series from the moored instruments cover a spectral range of 5 orders from 𝒪(101 s) to 𝒪(106 s). The objective of this article is to provide an overview of the huge data set which has been utilised by various studies, focusing on (i) water masses and circulation, (ii) operational forecasting, (iii) data assimilation, (iv) variability of the ocean, and (v) new payloads for gliders.
Online model calibration for a simplified LES model in pursuit of
real-time closed-loop wind farm control
Authors: Doekemeijer Bart , Boersma Sjoerd , Pao Lucy , Knudsen Torben , van Wingerden Jan-Willem
Published: April 2018

Abstract. Wind farm control often relies on computationally inexpensive surrogate models to predict the dynamics inside a farm. However, the reliability of these models over the spectrum of wind farm operation remains questionable due to the many uncertainties in the atmospheric conditions and tough-to-model flow dynamics at a range of spatial and temporal scales relevant for control. A closed-loop control framework is proposed in which a simplified dynamical LES model is calibrated and used for optimization in real time. This paper presents an estimation solution with an Ensemble Kalman filter (EnKF) at its core, which calibrates the surrogate model to the actual atmospheric conditions. The estimator is tested in high-fidelity simulations of a nine-turbine wind farm. Using exclusively turbine SCADA measurements, the adaptability to modeling errors and changes in atmospheric conditions (TI, wind speed) is shown. Convergence is reached within 400 seconds of operation, after which the estimation error in flow fields is negligible. At a low computational cost of 1.2 s on an 8-core CPU, this algorithm shows comparable accuracy to the state of the art from the literature while being approximately two orders of magnitude faster. Using the calibration solution presented, the surrogate model can be used for accurate forecasting and optimization.
II. Orígenes
Authors: Arredondo Erika
Published: April 2018

Configuraciones de lo sagrado en la literatura contemporánea del Cono Sur
A proposta de um guia de referência sobre Terminologia para estudantes de cursos de licenciatura em Letras através do processamento de corpus via WordSmith Tools
Authors: Delgado Heloísa Orsi Koch , Pasin Débora Montenegro , Rollsing Lucas Zambrano
Published: April 2018

Relatamos a etapa inicial da construção de um guia de referência sobre Terminologia para estudantes de cursos de licenciatura em Letras. Focamos na elaboração do corpus de estudo e das fichas terminológicas, as quais antecedem à obra per se. Utilizamos o WordSmith Tools para extrair as palavras-chave, a fim de, posteriormente, tornarem-se verbetes terminológicos. As palavras-chave foram obtidas de acordo com seu valor de chavicidade (razão estatística que caracteriza as palavras-chave oriundas da comparação de uma lista de palavras de um corpus de estudo com a lista de palavras de um corpus de referência). Para fins de amostra, trouxemos dois exemplos de fichas e seus respectivos verbetes.
O vocábulo1 presidenta sob análise em cinco dimensões correlatas: diacrônica, interlinguística, normativa, morfológica e sociopolítica
Authors: Cavalcante Sávio André de Souza , Coan Márluce
Published: April 2018

Analisamos, neste artigo, sob os vieses qualitativo e quantitativo, o vocábulo presidenta, que, tomando por base sua forma latina, não apresentaria variação; contudo, a validade do termo justifica-se por diversos critérios: (i) a língua abriga variação e mudança; (ii) a variação presidente/presidenta, em Português (brasileiro e europeu), também é notada em veículos midiáticos das demais línguas românicas: Francês, Italiano, Espanhol e Romeno; (iii) há menção ao vocábulo em obras de referência, (iv) que também apresentam possibilidade de variação a outras palavras terminadas em -e; (v) a variação é comprovada em dados reais, sendo o vocábulo presidenta fortemente motivado por posição político-partidária.
Estudos em avaliatividade no Brasil: panorama 2005-2017
Authors: Almeida Fabiola Aparecida Sartin Dutra Pereira , Vian Jr Orlando
Published: April 2018

Este artigo apresenta um panorama de estudos no Brasil sobre o sistema de avaliatividade (MARTIN; WHITE, 2005). Foram levantados trabalhos em dissertações e teses e em artigos publicados em revistas Qualis A1, A2, B1 e B2. Após considerações teóricas sobre o sistema e seus subsistemas, apresentamos o quantitativo dos itens levantados com o intuito de contribuir para uma visão geral dos estudos acerca do sistema de avaliatividade em nosso contexto, além de socializar pesquisas sobre o tema com estudiosos da Linguística Sistêmico-Funcional. Os resultados revelam a produtividade em estudos sobre o tema no campo dos estudos linguísticos no Brasil.
BAS: Beetle Antennae Search Algorithm for Optimization Problems
Authors: Jiang Xiangyuan , Li Shuai
Published: April 2018

Meta-heuristic algorithms have become very popular because of powerful performance on the optimization problem. A new algorithm called beetle antennae search algorithm (BAS) is proposed in the paper inspired by the searching behavior of long-horn beetles. The BAS algorithm imitates the function of antennae and the random walking mechanism of beetles in nature, and then two main steps of detecting and searching are implemented. Finally, the algorithm is benchmarked on 2 well-known test functions, in which the numerical results validate the efficacy of the proposed BAS algorithm.