bluuebunny/crossref_metadata_2025 huggingface dataset:
Space-charge limited conduction in epitaxial chromia films grown on elemental and oxide-based metallic substrates
Authors: Kwan C.-P. , Street M. , Mahmood A. , Echtenkamp W. , Randle M. , He K. , Nathawat J. , Arabchigavkani N. , Barut B. , Yin S. , Dixit R. , Singisetti U. , Binek Ch. , Bird J. P.
Published: May 2019

We study temperature dependent (200 – 400 K) dielectric current leakage in high-quality, epitaxial chromia films, synthesized on various conductive substrates (Pd, Pt and V2O3). We find that trap-assisted space-charge limited conduction is the dominant source of electrical leakage in the films, and that the density and distribution of charge traps within them is strongly dependent upon the choice of the underlying substrate. Pd-based chromia is found to exhibit leakage consistent with the presence of deep, discrete traps, a characteristic that is related to the known properties of twinning defects in the material. The Pt- and V2O3-based films, in contrast, show behavior typical of insulators with shallow, exponentially-distributed traps. The highest resistivity is obtained for chromia fabricated on V2O3 substrates, consistent with a lower total trap density in these films. Our studies suggest that chromia thin films formed on V2O3 substrates are a promising candidate for next-generation spintronics.
Elastic anomalies associated with domain switching in BaTiO3 single crystals under in situ electrical cycling
Authors: Pesquera D. , Casals B. , Thompson J. E. , Nataf G. F. , Moya X. , Carpenter M. A.
Published: May 2019

The elastic response of BaTiO3 single crystals during electric field cycling at room temperature has been studied using in situ Resonant Ultrasound Spectroscopy (RUS), which allows monitoring of both the elastic and anelastic changes caused by ferroelectric polarization switching. We find that the first ferroelectric switching of a virgin single crystal is dominated by ferroelastic 90° switching. In subsequent ferroelectric switching, ferroelastic switching is reduced by domain pinning and by the predominance of 180° ferroelectric domains, as confirmed by polarized light microscopy. RUS under in situ electric field therefore demonstrates to be an effective technique for the investigation of electromechanical coupling in ferroelectrics.
Full-field Fourier ptychography (FFP): Spatially varying pupil modeling and its application for rapid field-dependent aberration metrology
Authors: Song Pengming , Jiang Shaowei , Zhang He , Huang Xizhi , Zhang Yongbing , Zheng Guoan
Published: May 2019

Digital aberration measurement and removal play a prominent role in computational imaging platforms aimed at achieving simple and compact optical arrangements. A recent important class of such platforms is Fourier ptychography (FP), which is geared toward efficiently creating gigapixel images with high resolution and large field of view (FOV). In current FP implementations, pupil aberration is often recovered at each small segment of the entire FOV. This reconstruction strategy fails to consider the field-dependent nature of the optical pupil. Given the power series expansion of the wavefront aberration, the spatially varying pupil can be fully characterized by tens of coefficients over the entire FOV. With this observation, we report a Full-field Fourier Ptychography (FFP) scheme for rapid and robust aberration metrology. The meaning of “full-field” in FFP is referred to the recovery of the “full-field” coefficients that govern the field-dependent pupil over the entire FOV. The optimization degrees of freedom are at least two orders of magnitude lower than the previous implementations. We show that the image acquisition process of FFP can be completed in ∼1 s and the spatially varying aberration of the entire FOV can be recovered in ∼35 s using a central processing unit. The reported approach may facilitate the further development of FP. Since no moving part or calibration target is needed in this approach, it may find important applications in aberration metrology. The derivation of the full-field coefficients and its extension for Zernike modes also provide a general tool for analyzing spatially varying aberrations in computational imaging systems.
Study on the reinforcing effect of nano-SiO2 filled PTFE composites
Authors: Han Yi , Zheng Bo , Chen Jihong , He Qiang
Published: May 2019

The wear behavior and coefficient of friction for Nano-SiO2 filled polytetrafluoroethylene (PTFE) was investigated under dry conditions. The ball indentation hardness, tensile strength and elongation at break were determined. It was found that both ball indentation hardness and tensile properties were better reinforced by nano-SiO2 particles. The tribological properties of the nano-SiO2 PTFE composite and the regular SiO2 PTFE composite were compared for several applied loads. The worn surfaces were examined by means of scanning electron microscopy (SEM) and 3D profilometry. It was determined that the wear rate of PTFE composites filled with Nano-SiO2 particles considerably decreased. The friction forces were found to be lower for the Nano-SiO2 filled composites than those in the regular particles composite for the same experimental conditions.
An optimized twist angle to find the twist-averaged correlation energy applied to the uniform electron gas
Authors: Mihm Tina N. , McIsaac Alexandra R. , Shepherd James J.
Published: May 2019

We explore an alternative to twist averaging in order to obtain more cost-effective and accurate extrapolations to the thermodynamic limit (TDL) for coupled cluster doubles (CCD) calculations. We seek a single twist angle to perform calculations at, instead of integrating over many random points or a grid. We introduce the concept of connectivity, a quantity derived from the nonzero four-index integrals in an MP2 calculation. This allows us to find a special twist angle that provides appropriate connectivity in the energy equation, which yields results comparable to full twist averaging. This special twist angle effectively makes the finite electron number CCD calculation represent the TDL more accurately, reducing the cost of twist-averaged CCD over Ns twist angles from Ns CCD calculations to Ns MP2 calculations plus one CCD calculation.
van der Waals epitaxy of Mn-doped MoSe2 on mica
Authors: Dau M. T. , Vergnaud C. , Gay M. , Alvarez C. J. , Marty A. , Beigné C. , Jalabert D. , Jacquot J.-F. , Renault O. , Okuno H. , Jamet M.
Published: May 2019

The magnetic order associated with the degree of freedom of spin in two-dimensional (2D) materials is subjected to intense investigation because of its potential application in 2D spintronics and valley-related magnetic phenomena. We report here a bottom-up strategy using molecular beam epitaxy to grow and dope large-area (cm2) few-layer MoSe2 with Mn as a magnetic dopant. High-quality Mn-doped MoSe2 layers are obtained for Mn content of less than 5% (atomic). When increasing the Mn content above 5%, we observe a clear transition from layer-by-layer to cluster growth. Magnetic measurements, involving a transfer process of the cm2-large doped layers on 100-micron-thick silicon substrate, show plausible proof of high-temperature ferromagnetism of 1% and 10% Mn-doped MoSe2. Although we could not point to a correlation between magnetic and electrical properties, we demonstrate that the transfer process described in this report permits to achieve conventional electrical and magnetic measurements on the doped layers transferred on any substrate. Therefore, this study provides a promising route to characterize stable ferromagnetic 2D layers, which is broadening the current start-of-the-art of 2D materials-based applications.
Synaptic behaviors of electromigrated Au nanogaps
Authors: Sakai Keita , Sato Tomomi , Tani Soki , Ito Mitsuki , Yagi Mamiko , Shirakashi Jun-ichi
Published: May 2019

Artificial electronic synapses or synaptic devices, which are capable of mimicking the functions of biological synapses in the human brain, are considered the basic building blocks for brain-inspired computing. Therefore, we investigated the emulation of synaptic functions in a simple Au nanogap. The synaptic functionality of neuromorphic hardware originates from a gradually modulated resistance. Previously, we investigated simple electromigration-based methods for controlling the tunnel resistance of nanogaps, called activation. In this study, a new type of artificial synaptic device based on planar Au nanogaps is demonstrated using a newly investigated activation procedure with voltage pulses. In the activation method with specific voltage pulses, the change in tunnel resistance of the Au nanogaps can be gradually controlled depending on the interval and amplitude of input voltage pulses. Moreover, Au inorganic synapses can emulate the synaptic functions of both short-term plasticity (STP) and long-term plasticity (LTP) characteristics. After the applied pulse is removed, the current decays rapidly at the beginning, followed by a gradual fade to a stable level. In addition, with repeated stimulations, the forgetting rate becomes decreases and the memory retention increases. Therefore, we observe an effect analogous to a memory transition from STP to LTP in biological systems. Our results may contribute to the development of highly functional artificial synapses and the further construction of neuromorphic computing architecture.
Investigation of the band alignment at MoS2/PtSe2 heterojunctions
Authors: Wang Wenjia , Li Kuilong , Wang Yang , Jiang Wenxin , Liu Xingyu , Qi Han
Published: May 2019

In this work, large-area continuous monolayer-MoS2 and triple-layer-PtSe2 films are grown on Si substrates by chemical vapor deposition and the MoS2/PtSe2 heterostructures are fabricated using transfer technology. The energy band alignment at the heterojunction is investigated by employing x-ray photoelectron spectroscopy measurements, indicating a type-I band formed at the interface. The conduction and valence band offsets are determined to be 0.85 eV and 0.66 eV, respectively, which is consistent with the results deduced from the electron affinity. Furthermore, the enhancing improvement of light absorption in the visible region implies that this heterostructure has great potential in optoelectronic applications. This study provides promising guidance for the related device design and fabrication.
Stable zigzag and tripodal all-nitrogen anion N44− in BeN2
Authors: Lin Jiani , Zhu Zuoqin , Jiang Qiwen , Guo Shitai , Li Jianfu , Zhu Hongyang , Wang Xiaoli
Published: May 2019

All-nitrogen anions have attracted extensive attention because of their unique chemical and physical properties, and potential applications as high-energy density materials. Here, we discovered two N44- anions with planar zigzag and tripodal structures in BeN2 compound using first-principle calculations with structural search. At ambient conditions, both of them have high kinetic and thermodynamic stability with high energy density (2.48 kJ/g, and 2.95 kJ/g relative to Be3N2 and N2 gas). The zigzag N44− anion has P21/c space group in BeN2 compound and is energetically favorite in the pressure range of 0−48 GPa. While tripodal N44− anion has Cm space group and is energetically favorite in the pressure range of 48−100 GPa. Further analysis of chemical bonding pattern and electronic properties show that the Be atoms provide 2s electrons to alter the bonding state of N44− as well as use empty outer shell 2p orbital to accommodate lone pair electrons of N atoms, forming coordinate bonds to stabilize the compounds. More important, the calculated formation of enthalpies indicate that the zigzag and tripodal N44− can be synthesized via compressing Be3N2 and N2 at a modest pressure. Our results provide a scheme to synthesis N44- anions and stabilize all-nitrogen anions by introducing beryllium atoms.
Isomorph invariance and thermodynamics of repulsive dense bi-Yukawa one-component plasmas
Authors: Lucco Castello F. , Tolias P. , Hansen J. S. , Dyre J. C.
Published: May 2019

In numerous realizations of complex plasmas, dust-dust interactions are characterized by two screening lengths and are thus better described by a combination of Yukawa potentials. The present work investigates the static correlations and the thermodynamics of repulsive dense bi-Yukawa fluids based on the fact that such strongly coupled systems exhibit isomorph invariance. The strong virial-potential energy correlations are demonstrated with the aid of molecular dynamics simulations, an accurate analytical expression for the isomorph family of curves is obtained, and an empirical expression for the fluid-solid phase-coexistence line is proposed. The isomorph-based empirically modified hypernetted-chain approach, grounded on the ansatz of isomorph invariant bridge functions, is then extended to such systems and the resulting structural properties show an excellent agreement with the results of computer simulations. A simple and accurate closed-form expression is obtained for the excess internal energy of dense bi-Yukawa fluids by capitalizing on the compact parameterization offered by the Rosenfeld-Tarazona decomposition in combination with the Rosenfeld scaling, which opens up the energy route to thermodynamics.
Epigenetic upregulation of FKBP5 by aging and stress contributes to NF-κB–driven inflammation and cardiovascular risk
Authors: Zannas Anthony S. , Jia Meiwen , Hafner Kathrin , Baumert Jens , Wiechmann Tobias , Pape Julius C. , Arloth Janine , Ködel Maik , Martinelli Silvia , Roitman Maria , Röh Simone , Haehle Andreas , Emeny Rebecca T. , Iurato Stella , Carrillo-Roa Tania , Lahti Jari , Räikkönen Katri , Eriksson Johan G. , Drake Amanda J. , Waldenberger Melanie , Wahl Simone , Kunze Sonja , Lucae Susanne , Bradley Bekh , Gieger Christian , Hausch Felix , Smith Alicia K. , Ressler Kerry J. , Müller-Myhsok Bertram , Ladwig Karl-Heinz , Rein Theo , Gassen Nils C. , Binder Elisabeth B.
Published: May 2019

Aging and psychosocial stress are associated with increased inflammation and disease risk, but the underlying molecular mechanisms are unclear. Because both aging and stress are also associated with lasting epigenetic changes, a plausible hypothesis is that stress along the lifespan could confer disease risk through epigenetic effects on molecules involved in inflammatory processes. Here, by combining large-scale analyses in human cohorts with experiments in cells, we report that FKBP5, a protein implicated in stress physiology, contributes to these relations. Across independent human cohorts (total
n
> 3,000), aging synergized with stress-related phenotypes, measured with childhood trauma and major depression questionnaires, to epigenetically up-regulate
FKBP5
expression. These age/stress-related epigenetic effects were recapitulated in a cellular model of replicative senescence, whereby we exposed replicating human fibroblasts to stress (glucocorticoid) hormones. Unbiased genome-wide analyses in human blood linked higher
FKBP5
mRNA with a proinflammatory profile and altered NF-κB–related gene networks. Accordingly, experiments in immune cells showed that higher
FKBP5
promotes inflammation by strengthening the interactions of NF-κB regulatory kinases, whereas opposing FKBP5 either by genetic deletion (CRISPR/Cas9-mediated) or selective pharmacological inhibition prevented the effects on NF-κB. Further, the age/stress-related epigenetic signature enhanced
FKBP5
response to NF-κB through a positive feedback loop and was present in individuals with a history of acute myocardial infarction, a disease state linked to peripheral inflammation. These findings suggest that aging/stress-driven FKBP5–NF-κB signaling mediates inflammation, potentially contributing to cardiovascular risk, and may thus point to novel biomarker and treatment possibilities.
Ice sheet contributions to future sea-level rise from structured expert judgment
Authors: Bamber Jonathan L. , Oppenheimer Michael , Kopp Robert E. , Aspinall Willy P. , Cooke Roger M.
Published: May 2019

Despite considerable advances in process understanding, numerical modeling, and the observational record of ice sheet contributions to global mean sea-level rise (SLR) since the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change, severe limitations remain in the predictive capability of ice sheet models. As a consequence, the potential contributions of ice sheets remain the largest source of uncertainty in projecting future SLR. Here, we report the findings of a structured expert judgement study, using unique techniques for modeling correlations between inter- and intra-ice sheet processes and their tail dependences. We find that since the AR5, expert uncertainty has grown, in particular because of uncertain ice dynamic effects. For a +2 °C temperature scenario consistent with the Paris Agreement, we obtain a median estimate of a 26 cm SLR contribution by 2100, with a 95th percentile value of 81 cm. For a +5 °C temperature scenario more consistent with unchecked emissions growth, the corresponding values are 51 and 178 cm, respectively. Inclusion of thermal expansion and glacier contributions results in a global total SLR estimate that exceeds 2 m at the 95th percentile. Our findings support the use of scenarios of 21st century global total SLR exceeding 2 m for planning purposes. Beyond 2100, uncertainty and projected SLR increase rapidly. The 95th percentile ice sheet contribution by 2200, for the +5 °C scenario, is 7.5 m as a result of instabilities coming into play in both West and East Antarctica. Introducing process correlations and tail dependences increases estimates by roughly 15%.
Machine learning reveals systematic accumulation of electric current in lead-up to solar flares
Authors: Dhuri Dattaraj B. , Hanasoge Shravan M. , Cheung Mark C. M.
Published: May 2019

Significance

Reliable flare forecasting is essential for improving preparedness for severe space weather consequences. Flares also serve as probes of solar magnetic processes and the emergence of flux at the solar surface. Training machine-learning (ML) algorithms using magnetic-field observations for improving flare forecasting has been extensively studied in prior literature. Instead, here we use ML to understand the underlying mechanisms governing flares. We train ML algorithms to classify flaring and nonflaring active regions (ARs) with high fidelity and report statistical trends for AR evolution days before and after M- and X-class flares. These trends are interpreted in terms of existing models of subsurface magnetic field and flux emergence. Our results also provide hypotheses for achieving reliable flare forecasting.
Short-interval severe fire erodes the resilience of subalpine lodgepole pine forests
Authors: Turner Monica G. , Braziunas Kristin H. , Hansen Winslow D. , Harvey Brian J.
Published: May 2019

Subalpine forests in the northern Rocky Mountains have been resilient to stand-replacing fires that historically burned at 100- to 300-year intervals. Fire intervals are projected to decline drastically as climate warms, and forests that reburn before recovering from previous fire may lose their ability to rebound. We studied recent fires in Greater Yellowstone (Wyoming, United States) and asked whether short-interval (<30 years) stand-replacing fires can erode lodgepole pine (Pinus contortavar.latifolia) forest resilience via increased burn severity, reduced early postfire tree regeneration, reduced carbon stocks, and slower carbon recovery. During 2016, fires reburned young lodgepole pine forests that regenerated after wildfires in 1988 and 2000. During 2017, we sampled 0.25-ha plots in stand-replacing reburns (n= 18) and nearby young forests that did not reburn (n= 9). We also simulated stand development with and without reburns to assess carbon recovery trajectories. Nearly all prefire biomass was combusted (“crown fire plus”) in some reburns in which prefire trees were dense and small (≤4-cm basal diameter). Postfire tree seedling density was reduced sixfold relative to the previous (long-interval) fire, and high-density stands (>40,000 stems ha−1) were converted to sparse stands (<1,000 stems ha−1). In reburns, coarse wood biomass and aboveground carbon stocks were reduced by 65 and 62%, respectively, relative to areas that did not reburn. Increased carbon loss plus sparse tree regeneration delayed simulated carbon recovery by >150 years. Forests did not transition to nonforest, but extreme burn severity and reduced tree recovery foreshadow an erosion of forest resilience.
Structural and functional analyses of the N-terminal domain of the A subunit of aBacillus megateriumspore germinant receptor
Authors: Li Yunfeng , Jin Kai , Perez-Valdespino Abigail , Federkiewicz Kyle , Davis Andrew , Maciejewski Mark W. , Setlow Peter , Hao Bing
Published: May 2019

Germination ofBacillusspores is induced by the interaction of specific nutrient molecules with germinant receptors (GRs) localized in the spore’s inner membrane. GRs typically consist of three subunits referred to as A, B, and C, although functions of individual subunits are not known. Here we present the crystal structure of the N-terminal domain (NTD) of the A subunit of theBacillus megateriumGerK3GR, revealing two distinct globular subdomains bisected by a cleft, a fold with strong homology to substrate-binding proteins in bacterial ABC transporters. Molecular docking, chemical shift perturbation measurement, and mutagenesis coupled with spore germination analyses support a proposed model that the interface between the two subdomains in the NTD of GR A subunits serves as the germinant binding site and plays a critical role in spore germination. Our findings provide a conceptual framework for understanding the germinant recruitment mechanism by which GRs trigger spore germination.
Characteristics evaluation of SiC/Si nanocomposites produced by spark plasma sintering
Authors: Heydarian Abtin , Sajjadi Seyed Abdolkarim , Kern Frank , Johnsson Mats
Published: May 2019

SiC–Si composites are widely used either as a bulk material or as a matrix for fibre reinforced ceramics. In the current research, nanocomposites of SiC–Si with different volume fractions of Si were sintered by spark plasma sintering (SPS) for the first time. The effect of Si content and different sintering parameters on relative density, microstructure, hardness and fracture toughness of the sintered materials have been investigated. The relative density increased from about 83 to 99% by increasing the sintering temperature to 1700°C, sintering time to 10 min, and pressure to 70 MPa for composites containing >20 vol.-% Si. The results revealed that the full dense SiC–20 vol.-%Si composite can be obtained by SPS at 1700°C, 10 min and 70 MPa. Moreover, in this condition, the hardness and toughness of the composites reached the optimum values.
Cooling effects on microstructure and mechanical properties of 27Cr–4Mo–2Ni ferritic stainless steel
Authors: Guo Hong-Kui , Lu Hui-Hu , Zhang Wang-Gang , Meng Li-Xin , Liang Wei
Published: May 2019

The effects of cooling manner on the microstructure and mechanical properties of 27Cr–4Mo–2Ni ferritic stainless steel were investigated. It was found that the Laves phase (except for the TiN and Nb(C, N) particles) was distributed both in the grains and at the grain boundaries in the furnace-cooled specimen. The water-quenched and air-cooled specimens showed only TiN and Nb(C, N) particles. After annealing at 1100°C, the furnace-cooled specimen showed significant grain coarsening as compared to the water-quenched and air-cooled specimens. Furthermore, the Vickers hardness of the furnace-cooled specimen increased, while the total elongation decreased because of the formation of the Laves phase. The precipitation of the Laves phase resulted in the brittle fracture of the specimen during the tensile test.
The Fatigue and Fitness Test for Teams (FFITT): A practical option for monitoring athletes in a team as individuals
Authors: Starling Lindsay T. , Nellemann Stacy , Parkes Andrew , Lambert Michael I.
Published: May 2019

We developed the Fatigue and Fitness Test for Teams (FFITT) to address the challenges of monitoring players in a team simultaneously. The test, which takes 8 min for the entire team, incorporates subjective measures of well‐being (RTT‐Q), and objective measures of the autonomic system (HRR60s) and neuromuscular function (SLJ). The aim of this study was to present the rationale for the FFITT as a novel athlete monitoring protocol and to measure the reliability of each component of the test. The internal consistency of the RTT‐Q questions ranged from α = 0.69–0.92. All questions had an α > 0.83, with one exception of question ‘Rate the well‐being/stress your school/university/work is causing you to feel’ which had an α = 0.69. The reliability of the HRR60s and SLJ was high (R = 0.92, and 0.91 respectively). The absolute typical error of measurement (TEM) of the SLJ was 8 cm and HRR60s was 3 beats. When expressed relatively the CVTEM of HRR60s was 8.4% and SLJ was 3.0%. Based on the TEM the HRR60s and SLJ could detect medium and large changes in fatigue and fitness. In absolute terms this equates to more than 5 bpm (HRR60s) and more than 13 cm (SLJ). The FFITT has the potential to satisfy both scientific principles and the coach's demands of a practical monitoring protocol for frequent use in a team.
The credibility of environmental problems in Argentina and Spain/ La credibilidad de los problemas ambientales en Argentina y España
Authors: Sarabia-Sánchez Francisco J. , Bianchi Enrique-Carlos
Published: May 2019

The purpose of this study is to analyse the credibility of the content of the message and that of news stories about environmental problems, comparing the cases of Argentina and Spain. Its novel contribution is that it also analyses credibility according to the generation to which the informant belongs. In Argentina, information was compiled by means of an online survey ( NArgentina = 450), whereas in Spain the same survey was conducted by interviewers ( NSpain = 493). Low levels of credibility were found for the contents of messages about environmental problems and also for the news stories and narratives generated around them. Significant differences were noted between Argentina and Spain in relation to the credibility of the content of the message (which is greater in Argentina) but not in the credibility of news stories about environmental problems. In contrast to expectations, no generational differences were found in the two countries with regard to either type of credibility. This paper discusses the implications of the lack of generational segmentation as well as the low levels of credibility detected.
Machine Learning to Instruct Single Crystal Growth by Flux Method*
Authors: Yao Tang-Shi , Tang Cen-Yao , Yang Meng , Zhu Ke-Jia , Yan Da-Yu , Yi Chang-Jiang , Feng Zi-Li , Lei He-Chang , Li Cheng-He , Wang Le , Wang Lei , Shi You-Guo , Sun Yu-Jie , Ding Hong
Published: May 2019

Growth of high-quality single crystals is of great significance for research of condensed matter physics. The exploration of suitable growing conditions for single crystals is expensive and time-consuming, especially for ternary compounds because of the lack of ternary phase diagram. Here we use machine learning (ML) trained on our experimental data to predict and instruct the growth. Four kinds of ML methods, including support vector machine (SVM), decision tree, random forest and gradient boosting decision tree, are adopted. The SVM method is relatively stable and works well, with an accuracy of 81% in predicting experimental results. By comparison, the accuracy of laboratory reaches 36%. The decision tree model is also used to reveal which features will take critical roles in growing processes.
DREENA-C framework: joint RAA and v2 predictions and implications to QGP tomography
Authors: Zigic Dusan , Salom Igor , Auvinen Jussi , Djordjevic Marko , Djordjevic Magdalena
Published: May 2019

In this paper, we presented our recently developed Dynamical Radiative and Elastic ENergy loss Approach (DREENA-C) framework, which is a fully optimized computational suppression procedure based on our state-of-the-art dynamical energy loss formalism in constant temperature finite size QCD medium. With this framework, we have generated, for the first time, joint R

AA
and v
2 predictions within our dynamical energy loss formalism. The predictions are generated for both light and heavy flavor probes, and different centrality regions in Pb + Pb collisions at the LHC, and compared with the available experimental data. While R

AA
predictions agree with experimental data, v
2 predictions qualitatively agree with, but are quantitatively visibly above, the experimental data (in disagreement with other models, which underestimate v
2). Consistently with numerical predictions, through simple analytic analysis, we show that R

AA
is insensitive to medium evolution (though highly sensitive to energy loss mechanisms), while v
2 is highly sensitive to the evolution. As a major consequence for precision quark-gluon plasma (QGP) tomography, this then leaves a possibility to calibrate energy loss models on R

AA
data, while using v
2 to constrain QGP parameters that are in agreement with both high and low p
⊥ data.
Building a job-exposure matrix for early plutonium workers at the Sellafield nuclear site, United Kingdom
Authors: Riddell Anthony , Wakeford Richard , Liu Hanhua , O’Hagan Jacqueline , MacGregor David , Agius Raymond , Wilson Christine , Peace Mark , de Vocht Frank
Published: May 2019

The potential for adverse health effects from internal exposure to Plutonium has been recognised since its discovery in the 1940s. However, in the absence of specific information, potential risks from Plutonium exposure have always largely been controlled through knowledge of radiation exposure risks in general, much of which comes from external radiation exposures. To try to obtain more direct estimates of potential internal exposure risks, epidemiological studies of Plutonium workers need to be conducted. Such epidemiological analyses require individual Plutonium exposure estimates that are as accurate and unbiased as possible. The UK Sellafield workforce includes one of the world’s largest cohorts of Plutonium workers, which constitutes, by some considerable margin, the group of workers most comprehensively monitored for internal exposure to this alpha-particle-emitter. However, for several hundred workers employed at the start of Plutonium work at the facility, during the period from 1952 through to 1963, the historical urinalysis results available cannot provide sufficiently accurate and unbiased exposure assessments needed for use in epidemiological studies. Consequently, these early workers have had to be excluded from epidemiological analyses and this has significantly reduced the power of these studies. A promising quantitative methodology to overcome the issue of missing or deficient exposure data, is to use exposure data from other sources to estimate the average exposure a ‘typical worker’ would have received, and to collate this information for specific occupations and years. This approach is called a Job-Exposure Matrix (JEM). Work on a pilot study to construct a population-specific quantitative JEM for the early Plutonium workers at Sellafield during 1952–1963, for whom reliable urinalysis results do not exist, has shown the potential for a JEM approach to produce more reliable and useful exposure estimates for epidemiological research.
Analyzing the cross slip motion of screw dislocations at finite temperatures in body-centered-cubic metals: molecular statics and dynamics studies
Authors: Suzudo Tomoaki , Onitsuka Takashi , Fukumoto Ken-ichi
Published: May 2019

The plasticity of body-centered-cubic metals at low temperatures is substantially determined by the screw-dislocation kinetics. Because the core of screw dislocations in these metals has a non-planar structure, its motion is complex. For example, although density functional theory predicts slip on a {110} plane, the actual slip plane at elevated temperatures differs from the prediction. In this work, we explored state-of-the-art atomistic modeling methods and successfully reproduced the transition of the slip plane through a temperature increase. We then devised an algorithm to analyze the activation of dislocation jump over the Peierls barrier and discovered a possible origin of this unexpected phenomenon: thermal fluctuation leads to the kink-pair nucleation for cross slip jumps with no transition of the dislocation core structure.
Investigation of offshore wind farm layouts regarding wake effects and cable topology
Authors: Wade Bryce , Pereira Ricardo , Wade Cameron
Published: May 2019

Offshore wind energy is emerging as a large contributor to installed renewable energy capacity. In order to continue the momentum of its development, the offshore wind industry is looking to continually lower the levelized cost of electricity (LCOE). One area being explored in an effort to lower the LCOE of offshore wind generation is the optimization of the wind farm layout. Many of the offshore wind farm layout designs that exist today are structured in a rectilinear form where turbines are spaced evenly along columns and rows. This research explores the economic advantages of removing rectilinear constraints and optimizing the positions of the individual turbines within an offshore wind farm. At the core of achieving the research objective was the development of a model that is capable of simulating an existing offshore wind farm by converting representative wind farm data into an LCOE. The positions of the turbines within the wind farm can be modified using an optimization framework with the intent to minimize the LCOE. The model comprised of the Jensen Wake Model, a hybrid cable layout heuristic and a cost scaling model. The wind farm layout was optimized using a genetic algorithm. The cost estimation model and optimization framework were applied into two case studies to analyze the results of the wind farm layout optimization of two wind farms, Horns Rev and Borssele. In both case studies the optimized layouts provided higher AEP, shorter intra-array collection cable lengths and ultimately a lower LCOE than the baseline rectilinear layouts.
Computational fluid dynamics methodology for characterisation of leading edge erosion in whirling arm test rigs
Authors: Herring R , Dyer K , MacLeod A , Ward C
Published: May 2019

Blade leading edge erosion has developed into a significant issue for the offshore wind industry. Protection solutions, including polymer coatings and tapes, are often applied to increase the blade lifetime. Experimental evaluation of protection systems is typically conducted in whirling arm rain erosion test rigs. Currently, there is no thoroughly validated method to relate the test results to real-world erosion performance. Furthermore, the design of rigs is not sufficiently limited to enable comparison of results between different rigs. Industry guideline, DNV-GL-RP-0171, provides a comparison method to address this issue. This paper describes the development of a droplet particle tracking Computational Fluid Dynamics methodology for rain erosion test rigs, which models the impact strike characteristics of a droplet, the number of impacts and the effect of rig aerodynamics. The methodology was applied to two rigs with different aerodynamics. Rain erosion tests were conducted in the rigs on identical coating and aluminium samples. The results were compared against predicted number of impacts from the DNV-GL guideline. Contradictory results were found, concluding that the guideline does not provide an accurate comparison between all test rigs, as it does not account for rigs where large aerodynamic effects cause droplet concentrations or droplet break-up.
Nonlinear Estimation of Important Variables using Neural Network in Wind Farms
Authors: Hur Sung-Ho
Published: May 2019

Utilising additional variables, which are normally not measured, could bring significant improvements to condition monitoring and control of a wind turbine and farm. However, incorporating additional sensors to measure such variables could increase the cost significantly. As a solution, instead of equipping every turbine in the wind farm with an expensive sensor to measure such a variable, it is proposed that only one turbine be equipped with a sensor and the neighbouring turbines with an estimator that essentially replaces the sensor; that is, each estimator would subsequently estimate what the sensor would measure. Each estimator is constructed based on Neural Network, and as a result, the cost could be significantly reduced. Note that the only turbine equipped with a sensor is used to train the NN. This work presents the results of a preliminary study to examine the feasibility of the proposed approach.
Drift stability of HyStOH semi-submersible supported by airfoil shaped structures
Authors: Manjock A , Netzband S
Published: May 2019

This study presents the results of the German research project HyStOH funded by German Federal Ministry of Economic Affairs and Energy (BMWi). The project consortium of German universities, wind turbine designers, wind farm developers and certification bodies design a novel semi-submersible steel structure with a single point mooring and self-aligning capabilities. The tower, which carries a 6 MW two-bladed downwind turbine, has an airfoil shaped cover, which supports the self-alignment of the full structure towards the main wind direction. The downwind operating wind turbine in combination with the lift force generating tower enables a passive yaw system acting against hydrodynamical impacts from waves and currents. Simulations in time domain applying the fully coupled aero-hydro-servo-elastic code Bladed_4.8 demonstrate the drift sensitivity and the self-aligning capabilities of the HyStOH design. The hydrodynamic coefficients for the simulations have been adjusted by calculations with an 1:1 model of the panel code panMARE, developed by Technical University of Hamburg-Harburg. The motivation of this analysis is to capture the complex coupled motions of an innovative FOWT by numerical simulation tools [1]. The analysis presents dynamic simulations of the HyStOH design operating in turbulent wind and irregular sea state with special focus on the yaw drift behaviour of the FOWT. The sensitivity study of yaw drift is based on numerous variations of wind-wave-current misalignments during normal operation. The results of the simulations demonstrate the weathervane capabilities of the airfoil shaped structures.
Comparative Concept Design Study of Laterally Loaded Monopiles
Authors: Kaltekis K , Panagoulias S , van Dijk B F J , Brinkgreve R B J , Ramos da Silva M
Published: May 2019

Offshore wind turbine generators (WTG) are commonly founded on single large diameter piles, named monopiles. These monopiles are subjected to significant lateral loads and thereby sizeable overturning bending moments mainly due to action of wind and wave forces; thus the critical geotechnical design situation for monopiles supporting WTGs is often related to lateral loading conditions. The Pile Soil Analysis (PISA) joint industry research project [1] has recently proposed a monopile design method which encompasses finite element (FE) calculations under a specific design framework. Soil reaction curves that are crucial for monopile design (i.e. lateral force and moment reactions along the shaft and at the base of the pile) are derived from FE calculations, subsequently calibrated and entered into a 1D model which is then used for design optimisation. This method is implemented within the PLAXIS MoDeTo (Monopile Design Tool) software. This paper presents results of a concept monopile design study under lateral monotonic loading with the use of the PLAXIS MoDeTo method.
Investigation of Modelling Depths for an Electromechanical Simulation of a Direct-Drive Generator Considering Parasitic Airgap Forces and External Loads
Authors: Duda Tobias , Jacobs Georg , Bosse Dennis
Published: May 2019

This paper shows a multiphysical simulation approach for direct - drive generators, including electromagnetic force calculations and multibody simulation. The objective of this method is to determine the airgap width distribution of the generator during operation.

In this investigation different modelling depths of the electromechanical model are discussed. Especially the modelling of the electromagnetic force application and integration of flexible structural elements is discussed.
Parametric study of vane-type vortex generators under adverse pressure gradient by source term modelling in OpenFOAM
Authors: Errasti Iñigo , Fernández-Gamiz Unai , Martínez-Filgueira Pablo , Blanco Jesús María
Published: May 2019

The aim of the study is to analyse and characterize the primary vortices produced by single low profile vane-type vortex generators (VGs) of different heights positioned on a flat plate with a backward-facing ramp and adverse gradient pressure for an incident angle of 15º. The effect of the vortex generator is implemented by using a source term in the Navier-Stokes equations according to the so-called jBAY source term model. In order to carry out the parametric study of the primary vortex, Computational Fluid Dynamics (CFD) simulations have been performed for different VG heights using the Navier-Stokes equations at a Reynolds number of Reθ = 9100 based on the local boundary layer momentum thickness θ in open-source code OpenFOAM. As a preliminary result, the jBAY model reproduces relatively well the streamwise pressure coefficient distributions on the flat plate floor. Finally, the advantage of using this model over a fully mesh-resolved vortex generator model for certain cases must be remarked because a lower number of cells is needed in the model domain with a saving of computational time and resources.
Transferability of Operational Status Classification Models Among Different Wind Turbine Types
Authors: Trstanova Z. , Martinsson A. , Matthews C. , Jimenez S. , Leimkuhler B. , Van Delft T. , Wilkinson M.
Published: May 2019

A detailed understanding of wind turbine performance status classification can improve operations and maintenance in the wind energy industry. Due to different engineering properties of wind turbines, the standard supervised learning models used for classification do not generalize across data sets obtained from different wind sites. We propose two methods to deal with the transferability of the trained models: first, data normalization in the form of power curve alignment, and second, a robust method based on convolutional neural networks and feature-space extension. We demonstrate the success of our methods on real-world data sets with industrial applications.
Strawberry ripeness calibrated 2D colour lookup table for field-deployable computer vision
Authors: Mohamed Imran , Williams David , Stevens Richard , Dudley Richard
Published: May 2019

Efficient strawberry harvesting using semi-autonomous robotic pickers requires a method for fast, automatic discrimination between ripe and unripe berries. In this paper we present a strawberry ripeness algorithm that has been developed and tested on images obtained with commercial cameras, recorded under daylight illumination on an outdoor strawberry farm. The method uses a 2D lookup table seeded such that regions for ripe strawberry, unripe strawberry and strawberry calyx exist in distinct locations in the table. Measurements show the ratio of ripe to unripe area provides a good estimator of ripeness and that the approach was practical for further extension to real-time use.
Application of ISO 25178 standard for multiscale 3D parametric assessment of surface topographies
Authors: Marinello F , Pezzuolo A
Published: May 2019

The objective of the present work is to discuss the potential of areal surface texture parameters as introduced and discussed by ISO standards 25178, as a widely recognized reference framework of indices and procedures, which can help and accelerate understanding of functional information. Such indices have been developed specifically for the micro-scale, however they can be successfully implemented also in the case of larger scales. Parameters extraction takes place in three main steps, independently from the scale: calibration, filtering and parameter extraction. The possibility of using the same approach and the same roughness parameters at different scales helps very much not only the post processing of surfaces data sets but also their interpretation, putting the basis for multiscale models.
Analysis of the effects of uncertainties on agrometeorological models
Authors: Garinei A. , Marini A. , Piccioni E. , Marconi M. , Biondi L. , Bertolini A. , Ferrari G.
Published: May 2019

We analyze how the uncertainties in meteorological data affect the outcome of an agrometeorological model. In particular we focus on a model simulating the development of primary infections of downy mildew on grapevine. This model takes as inputs hourly measurements of temperature, relative humidity and rainfall and it simulates all the phases that eventually lead to the downy mildew primary infections. In order to assess the robustness of the model against the uncertainties of the input data we set up a Monte Carlo simulation. This procedure enhances the potentiality of the model since allows to extract, as an additional valuable piece of information, the probability of the infection event. The results we obtain are highly significant and suggest that the effects of the uncertainties are actually important and should be carefully evaluated.
Microsensors for the characterization of the insect gut environment
Authors: Crotti E
Published: May 2019

Microorganisms establish a wide range of symbiotic associations with their insect host, encompassing mutualistic, parasitic and commensal relationships. Insect gut microbiota is involved in many essential aspects of the host biology, physiology and behaviour. Factors such as pH, oxygen availability, retention time of the food and host innate immune system are important determinants of the gut symbionts’ colonization. Deciphering the interactions that take place and shape the symbiosis is an intriguing topic that cannot exclude the characterization of the physicochemical conditions occurring in the insect gut niche. Microsensors and microelectrodes can be usefully employed to characterize the physicochemical conditions occurring in the insect intestine, allowing to gain a better knowledge of the gut microenvironment in which the gut microbiota thrives.
A comparison of low-cost techniques for three-dimensional animal body measurement in livestock buildings
Authors: Pezzuolo A , Giora D , Guo H , Ma Q , Guercini S , Marinello F
Published: May 2019

Data about health and development of animals are still now mostly collected through manual measurements or visual observations but these kinds of methods of collecting data are causes of several problems. Alternatively, optical sensing techniques can be implemented in order to overcome limitations arising from manual contact measurements. The present research discusses metrological analysis of Structure from motion (SfM) photogrammetry approach, low-cost LiDAR scanning and Microsoft Kinect v1 depth camera to three-dimensional animal body measurement, with specific reference to pigs. Analyses were carried out on fiberglass model to get rid of animal movements. Scans were captured based on a segmented approach, where different portion of the body have been imaged during different frames acquisition tasks. The obtained results demonstrate the high potential of 3D Kinect. LiDAR show a higher RMS value respect to Kinect and SfM most probably due to the collection approach based on single profiles rather than on surfaces. Anyway, the RMS of relative noise ranges between 0.7 and 4 mm, showing a high accuracy of reconstructions even for the others techniques.