bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Metric of the Biological Carbon Pump: Number of Pump Passages and Its Control on Atmospheric pCO2
Authors: Holzer Mark , Kwon Eun Young , Pasquier Benoit
Published: May 2021

We develop novel locally defined diagnostics for the efficiency of the ocean's biological pump by tracing carbon throughout its lifetime in the ocean from gas injection to outgassing and counting the number of passages through the soft‐tissue and carbonate pumps. These diagnostics reveal that the biological pump's key controls on atmospheric pCO2 are the mean number of lifetime pump passages per dissolved inorganic carbon (DIC) molecule at the surface and the mean aphotic sequestration time of regenerated DIC. We apply our diagnostics to an observationally constrained carbon‐cycle model that features spatially varying stoichiometric ratios and is embedded in a data‐assimilated global ocean circulation. We find that for the present‐day ocean an average of 44 ± 4% of DIC in a given water parcel makes at least one lifetime passage through the soft tissue pump, and about 4% makes at least one passage through the carbonate pump. The global mean number of lifetime pump passages per molecule, including the fraction with zero passages, is and for the soft‐tissue and carbonate pumps. Using idealized perturbations to sweep out a sequence of states ranging from zero biological activity ( ppmv) to complete surface nutrient depletion ( ppmv), we find that fractional changes in are dominated by fractional changes in the number of soft‐tissue pump passages. At complete surface nutrient depletion, the mean fraction of DIC that has at least one lifetime passage through the soft‐tissue pump increases to 69 ± 5% with .
Anisotropy Variations in the Alaska Subduction Zone Based on Shear‐Wave Splitting From Intraslab Earthquakes
Authors: Richards Cole , Tape Carl , Abers Geoffrey A. , Ross Zachary E.
Published: May 2021

Shear‐wave splitting observations can provide insight into mantle flow, due to the link between the deformation of mantle rocks and their direction‐dependent seismic wave velocities. We identify anisotropy in the Cook Inlet segment of the Alaska subduction zone by analyzing splitting parameters of S waves from local intraslab earthquakes between 50 and 200 km depths, recorded from 2015–2017 and emphasizing stations from the Southern Alaska Lithosphere and Mantle Observation Network experiment. We classify 678 high‐quality local shear‐wave splitting observations into four regions, from northwest to southeast: (L1b) splitting measurements parallel to Pacific plate motion, (L1a) arc‐perpendicular splitting pattern, (L2) sharp transition to arc‐parallel splitting, and (L3) splitting parallel to Pacific plate motion. Forward modeling of splitting from various mantle fabrics shows that no one simple model fully explains the observed splitting patterns. An A‐type olivine fabric with fast direction dipping 45° to the northwest (300°)—aligned with the dipping slab—predicts fast directions that fit L1a observations well, but not L2. The inability of the forward model fabrics to fit all the observed splitting patterns suggests that the anisotropy variations are not due to variable ray angles, but require distinct differences in the anisotropy regime below the arc, forearc, and subducting plate.
A Pulsed Oxygenation in Terminal Paleoproterozoic Ocean: Evidence From the Transition Between the Chuanlinggou and Tuanshanzi Formations, North China
Authors: Wei Beilei , Tang Dongjie , Shi Xiaoying , Lechte Maxwell , Zhou Limin , Zhou Xiqiang , Song Huyue
Published: May 2021

The mid‐Proterozoic (ca. 1.8–0.8 Ga) witnessed a period of stable carbon cycling and long stasis in eukaryotic evolution, which was commonly ascribed to the persistently low oxygen levels in the atmosphere‐ocean system. Recently, several pulsed marine oxygenations were identified from different continents, and presumed to have facilitated the short‐term diversification of eukaryotes in the early Mesoproterozoic Era. To test this hypothesis, an integrated study of iodine species [I/ (Ca + Mg)], paired carbon isotopes (δ13Ccarb and δ13Corg), and elemental abundances was conducted on the fossil‐bearing Tuanshanzi Formation (∼1.64–1.63 Ga), North China. The near‐zero I/(Ca + Mg) ratios (0.00 ± 0.01 μmol/mol) coupled with low δ13Corg (−30.2 ± 1.4‰) in the strata below the fossil‐bearing interval suggests anoxic conditions in shallow seawater. An increase of I/ (Ca + Mg) up to ∼1.54 μmol/mol coupled with a ∼2‰ negative shift in δ13Ccarb and a ∼11‰ positive excursion in δ13Corg in the fossil‐bearing interval point to an increased oxygen concentration. Above the fossil‐bearing interval, I/ (Ca + Mg) decrease to <0.5 μmol/mol, suggesting deoxygenation and a return to anoxic to suboxic conditions. Combined with relevant data from other mid‐Proterozoic sections of North China and Australia, these data likely indicate dynamic redox conditions in the shallow seawaters of this period, with multiple pulses in oxygenation in otherwise anoxic conditions. These pulsed oxygenations may have facilitated short‐term proliferation and diversification of early eukaryotes in shallow seawaters, but the overall low oxygen levels have impeded their continuous development and the rise to ecological dominance until late Neoproterozoic.
MMS Observations of Field Line Resonances Under Disturbed Solar Wind Conditions
Authors: Le G. , Chi P. J. , Strangeway R. J. , Russell C. T. , Slavin J. A. , Anderson B. , Nakamura R. , Plaschke F. , Torbert R. , Wilder F.
Published: May 2021

We report an observational study of magnetospheric field‐line resonances (FLRs) using multi‐point data from the Magnetospheric Multiscale (MMS) mission. We examine well‐defined FLR events in the frequency range ∼2–10 mHz observed under disturbed solar wind conditions, such as high‐speed solar wind streams and solar wind pressure pulses. We focus on their azimuthal wave numbers (m‐numbers) and spatial variations of the wave frequencies, and compare their occurrence characteristics and wave properties for insights into their energy sources. Under disturbed solar wind conditions, we have found supporting observations for both external and internal energy sources for the generation of FLRs. The FLRs associated with different energy sources appear to have different wave characteristics. Although mode coupling is very common (i.e., waves generally have both toroidal and poloidal components with variable relative amplitudes), our observations show that solar wind disturbances directly drive low‐m, toroidal mode dominated FLRs, but internal energy sources are inferred for high‐m, poloidal mode dominated FLRs. The frequencies of the toroidal and poloidal waves have different spatial variations as a function of the L‐value. The frequency of the toroidal mode waves can change continuously with L while the frequency of poloidal waves exhibits discrete spatial structure along L.
Characterizing the Distribution of Temperature and Normal Stress on Flash Heated Granite Surfaces at Seismic Slip Rates
Authors: Barbery M. R. , Chester F. M. , Chester J. S.
Published: May 2021

At seismic slip rates, flash‐weakening can significantly reduce the coefficient of friction, and the magnitude of weakening increases with surface temperature. To quantify the distribution of flash temperature, high‐speed double‐direct shear experiments were conducted on Westerly granite blocks using velocity steps from 1 mm/s to 900 mm/s at 9 MPa normal stress. We employed a high‐speed infrared camera to measure surface temperatures on the moving block during sliding, and utilized a novel sliding‐surface geometry to control the mm‐scale contact history. Following the initial weakening upon the velocity step, the blocks slide at a constant coefficient of friction. Surface temperatures are inhomogeneously distributed across the sliding surface, and increase with displacement. To determine the local normal stress distribution at the mm‐scale, we combine a one‐dimensional thermal model with conventional flash‐weakening models that incorporate a surface temperature‐dependence informed by the controlled, mm‐scale contact history. Early contacts experience local normal stress exceeding 40 times the applied normal stress. As sliding progresses, the local normal stress at the hottest contacts decreases as contact area increases, leading to local normal stresses ranging from 2 to 6 times the applied normal stress on most contacts by 30 mm of slip. Increases in surface temperature, which would decrease the coefficient of friction, are buffered by wear processes that increase contact area and decrease the local normal stress. Treatments of flash heating are advanced by incorporating improved characterization of the state of the sliding surface at the mm and larger scales during sliding.
Petrogenesis of Basaltic Lavas From the West Pacific Seamount Province: Geochemical and Sr‐Nd‐Pb‐Hf Isotopic Constraints
Authors: Yan Quanshu , Milan Luke , Saunders J. Edward , Shi Xuefa
Published: May 2021

In this study, we report new major and trace element, Sr‐Nd‐Pb‐Hf isotopic compositions and Ar‐Ar ages for basaltic lavas from seven poorly studied seamounts/guyots in the Western Pacific Seamount Province (WPSP). A review of new and published Ar‐Ar ages for seamounts/guyots confirm no linear age progression, as would be expected if these seamounts were produced by the Pacific Plate moving over a stationary mantle plume. These samples exhibit an alkalic character and can be produced by small‐degree partial melting of garnet pyroxenite with CO2. Their isotopic data identify four mantle end‐members (DMM, EMI, EMII, and HIMU) in the WPSP source region. These results confirm previous studies that invoke multiple contemporaneous plumelets in the region and a heterogeneous upper mantle reservoir which has been overprinted by multiple discrete hotspots, which create an anomalous and heterogeneous upper mantle because of mixing/overlapping EMI, EMII, and HIMU tracks, and age progressive volcanism is totally obscured. We propose a model where relict fragments of enriched mantle with distinct isotopic compositions residing in the upper mantle were a product of the formation of the adjacent large oceanic plateaus. These events introduce heterogeneity in the depleted mantle. The infiltration and metasomatism of these relict enriched components by carbonatitic fluids from the low‐velocity zone, create a source that then underwent small degrees of decompressional melting. The partial melts exploited pre‐existing lithospheric faults as an upwelling conduit and the resultant seafloor lava flows have obscured evidence to those pre‐existing lithospheric faults.
Long‐Term Trend of Equatorial Atlantic Zonal Sea Surface Temperature Gradient Linked to the Tropical Pacific Cold Tongue Mode Under Global Warming
Authors: Li Yang , Chen Quanliang , Xing Nan , Cheng Zhigang , Qi Yulei , Feng Fan , Li Minggang
Published: May 2021

The equatorial Atlantic zonal sea surface temperature (SST) gradient, which has significant climatic and biogeochemical effects, is closely associated with the equatorial Pacific zonal SST gradient through Walker circulation on seasonal and interannual time scales. However, discrepancies in current SST data sets mean that its long‐term trend is not well understood. Here, using multiple data sets, we find a robust weakening long‐term trend (i.e., greater warming in the east than west) in the equatorial Atlantic zonal SST gradient over the period 1900–2010 in all data sets. We also find that this weakening trend is closely linked to the tropical Pacific cold tongue mode (CTM), which corresponds to a strong increasing long‐term trend of zonal SST gradient along the equatorial Pacific (i.e., warming in the west and cooling in the east). Specifically, the long‐term cooling SST anomalies associated with the CTM modify the Walker circulation, and leads to weaker trade winds over the western equatorial Atlantic. These in turn deepen the thermocline in the eastern equatorial Atlantic, and cause the weakening long‐term trend of SST gradient along the equatorial Atlantic. The long‐term trend of the CTM is induced by ocean dynamical feedback in response to global warming, suggesting that global warming could affect the equatorial Atlantic zonal SST gradient via the CTM. Our results provide a novel explanation of the linkages between the long‐term trend of equatorial Atlantic zonal SST gradient and the CTM under global warming, which carries important implications for the relationship between global warming and the equatorial Atlantic zonal SST gradient.
In Search of the Optimal Atmospheric River Index for US Precipitation: A Multifactorial Analysis
Authors: Zhang Chen , Tung Wen‐wen , Cleveland William S.
Published: May 2021

Atmospheric rivers (ARs) affect surface hydrometeorology in the US West Coast and Midwest. We systematically sought optimal AR indices for expressing surface precipitation impacts within the Atmospheric River Tracking Method Intercomparison Project (ARTMIP) framework. We adopted a multifactorial approach. Four factors, moisture fields, climatological thresholds, shape criteria, and temporal thresholds, collectively generated 81 West Coast AR indices and 81 Midwest indices from January 1980 to June 2017. Two moisture fields were extracted from the MERRA‐2 data for ARTMIP: integrated water vapor transport (IVT) and integrated water vapor (IWV). Metrics for precipitation effects included two‐way summary statistics, relating the concurrence of AR and that of precipitation, per event averaged precipitation rate, and per event precipitation accumulation. We found that an optimal AR index for precipitation depends on the types of impact to be addressed, associated physical mechanisms in the affected regions, timing, and duration. In West Coast and Midwest, IWV‐based AR indices identified the most abundant AR event time steps, most accurately associated AR to days with precipitation, and represented the presence of precipitation the best. With a lower climatological threshold, they detected the most accumulated precipitation with the longest event duration. Longer duration thresholds also led to higher accumulated precipitation, holding other factors constant. IWV‐based indices are the overall choice for Midwest ARs under varying seasonal precipitation drivers. IVT‐based indices suitably capture the accumulation of intense orographic precipitation on the West Coast. Indices combining IVT and IWV identify the fewest, shortest, but most intense AR precipitation episodes.
Oversampling Reflectivity Observations From a Geostationary Precipitation Radar Satellite: Impact on Typhoon Forecasts Within a Perfect Model OSSE Framework
Authors: Taylor James , Okazaki Atsushi , Honda Takumi , Kotsuki Shunji , Yamaji Moeka , Kubota Takuji , Oki Riko , Iguchi Toshio , Miyoshi Takemasa
Published: May 2021

For the past two decades, precipitation radars (PR) onboard low‐orbiting satellites such as Tropical Rainfall Measuring Mission (TRMM) have provided invaluable insight into global precipitation variability and led to advancements in numerical weather prediction through data assimilation. Building upon this success, planning has begun on the next generation of satellite‐based PR instruments, with the consideration for a future geostationary‐based PR (GPR), bringing the advantage of higher observation frequency over previous and current PR satellites. Following the successful demonstration by a recent study to test the feasibility of a GPR to obtain three‐dimensional precipitation data, this study takes the first step to investigate the potential usefulness of GPR observations for numerical weather prediction by performing a perfect model observing system simulation experiment (OSSE) for a West Pacific tropical cyclone (TC). Data assimilation experiments are performed assimilating reflectivity observations obtained for a range of beam sampling spans, following a previous finding that oversampling improves observation quality. Results showed observations obtained with finer sampling spans of 5 km and 10 km were able to better capture key tropical cyclone features in analyses, including the eye, heavy rainfall associated with the eyewall, and outer convective rainbands. Results also showed that through increased moistening and upward velocity within the inner storm environment, assimilation of observations drove an intensification of the secondary circulation and deepening of the storm, leading to an improvement in TC intensity error. Intensity forecasts were found improved for assimilation of observations obtained with increasingly finer beam sampling span, suggesting an important benefit of oversampling.
Improved Constraints on Global Methane Emissions and Sinks Using δ13C‐CH4
Authors: Lan X. , Basu S. , Schwietzke S. , Bruhwiler L. M. P. , Dlugokencky E. J. , Michel S. E. , Sherwood O. A. , Tans P. P. , Thoning K. , Etiope G. , Zhuang Q. , Liu L. , Oh Y. , Miller J. B. , Pétron G. , Vaughn B. H. , Crippa M.
Published: May 2021

We study the drivers behind the global atmospheric methane (CH4) increase observed after 2006. Candidate emission and sink scenarios are constructed based on proposed hypotheses in the literature. These scenarios are simulated in the TM5 tracer transport model for 1984–2016 to produce three‐dimensional fields of CH4 and δ13C‐CH4, which are compared with observations to test the competing hypotheses in the literature in one common model framework. We find that the fossil fuel (FF) CH4 emission trend from the Emissions Database for Global Atmospheric Research 4.3.2 inventory does not agree with observed δ13C‐CH4. Increased FF CH4 emissions are unlikely to be the dominant driver for the post‐2006 global CH4 increase despite the possibility for a small FF emission increase. We also find that a significant decrease in the abundance of hydroxyl radicals (OH) cannot explain the post‐2006 global CH4 increase since it does not track the observed decrease in global mean δ13C‐CH4. Different CH4 sinks have different fractionation factors for δ13C‐CH4, thus we can investigate the uncertainty introduced by the reaction of CH4 with tropospheric chlorine (Cl), a CH4 sink whose abundance, spatial distribution, and temporal changes remain uncertain. Our results show that including or excluding tropospheric Cl as a 13 Tg/year CH4 sink in our model changes the magnitude of estimated fossil emissions by ∼20%. We also found that by using different wetland emissions based on a static versus a dynamic wetland area map, the partitioning between FF and microbial sources differs by 20 Tg/year, ∼12% of estimated fossil emissions.
Quadruple Collocation Analysis of In‐Situ, Scatterometer, and NWP Winds
Authors: Vogelzang Jur , Stoffelen Ad
Published: May 2021

Triple collocation is an established technique for retrieving linear calibration coefficients and observation error variances of a physical quantity observed simultaneously by three different observation systems. The formalism is extended to an arbitrary number of systems, and representativeness errors and associated cross‐covariances are included in a natural way. It is applied to quadruple collocations of ocean surface vector winds from two scatterometers (ASCAT‐A, ASCAT‐B, or ScatSat), buoy measurements, and NWP model forecasts. There are 15 possible sets of quadruple collocation equations, 12 of which are solvable for the essential variables (calibration coefficients, observation error variances, and common variance) as well as two additional error covariances, each set leading to a different solution. The quadruple collocation equations by themselves give little information on the representativeness errors involved; these have to be estimated using other methods. The spreading in the solutions is a measure of the accuracy of the underlying error model. Variation of the scale at which the spatial variances are evaluated yields an optimal scale of 100–200 km. From triple collocation subsets the error in the scatterometer error standard deviations is found to be 0.03–0.05 m s−1, more than expected on statistical grounds. A more precise determination requires an error model that better describes the data error properties.
Strong Local Evaporative Cooling Over Land Due to Atmospheric Aerosols
Authors: Chakraborty TC , Lee Xuhui , Lawrence David M.
Published: May 2021

Aerosols can enhance terrestrial productivity through increased absorption of solar radiation by the shaded portion of the plant canopy—the diffuse radiation fertilization effect. Although this process can, in principle, alter surface evaporation due to the coupling between plant water loss and carbon uptake, with the potential to change the surface temperature, aerosol‐climate interactions have been traditionally viewed in light of the radiative effects within the atmosphere. Here, we develop a modeling framework that combines global atmosphere and land model simulations with a conceptual diagnostic tool to investigate these interactions from a surface energy budget perspective. Aerosols increase the terrestrial evaporative fraction, or the portion of net incoming energy consumed by evaporation, by over 4% globally and as much as ∼40% regionally. The main mechanism for this is the increase in energy allocation from sensible to latent heat due to global dimming (reduction in global shortwave radiation) and slightly augmented by diffuse radiation fertilization. In regions with moderately dense vegetation (leaf area index >2), the local surface cooling response to aerosols is dominated by this evaporative pathway, not the reduction in incident radiation. Diffuse radiation fertilization alone has a stronger impact on gross primary productivity (+2.18 Pg C y−1 or +1.8%) than on land evaporation (+0.18 W m−2 or +0.48%) and surface temperature (−0.01 K). Our results suggest that it is important for land surface models to distinguish between quantity (change in total magnitude) and quality (change in diffuse fraction) of radiative forcing for properly simulating surface climate.
Salvage HLA-haploidentical hematopoietic stem cell transplantation with post-transplant cyclophosphamide for graft failure in non-malignant disorders
Authors: Albert Michael H. , Sirin Mehtap , Hoenig Manfred , Hauck Fabian , Schuetz Catharina , Bhattacharyya Rajat , Stepensky Polina , Jacoby Elad , Güngör Tayfun , Beier Rita , Schulz Ansgar
Published: May 2021

Graft failure requires urgent salvage HSCT, but there is no universally accepted approach for this situation. We investigated T-cell replete haploidentical HSCT with post-transplantation cyclophosphamide following serotherapy-based, radiation-free, reduced intensity conditioning in children with non-malignant disorders who had rejected their primary graft. Twelve patients with primary or secondary graft failure received T-cell replete bone marrow grafts from haploidentical donors and post-transplantation cyclophosphamide. The recommended conditioning regimen comprised rituximab 375 mg/m2, alemtuzumab 0.4 mg/kg, fludarabine 150 mg/m2, treosulfan 20–24 g/m2 and cyclophosphamide 29 mg/kg. After a median follow-up of 26 months (7–95), eleven of twelve patients (92%) are alive and well with complete donor chimerism in ten. Neutrophil and platelet engraftment were observed in all patients after a median of 18 days (15–61) and 39 days (15–191), respectively. Acute GVHD grade I was observed in 1/12 patients (8%) and mild chronic GVHD in 1/12 patients (8%). Viral reactivations and disease were frequent complications at 75% and 42%, respectively, but no death from infectious causes occurred. In summary, this retrospective analysis demonstrates that a post-transplantation cyclophosphamide-based HLA-haploidentical salvage HSCT after irradiation-free conditioning results in excellent engraftment and overall survival in children with non-malignant diseases.
A method for utilizing automated machine learning for histopathological classification of testis based on Johnsen scores
Authors: Ito Yurika , Unagami Mami , Yamabe Fumito , Mitsui Yozo , Nakajima Koichi , Nagao Koichi , Kobayashi Hideyuki
Published: May 2021

We examined whether a tool for determining Johnsen scores automatically using artificial intelligence (AI) could be used in place of traditional Johnsen scoring to support pathologists’ evaluations. Average precision, precision, and recall were assessed by the Google Cloud AutoML Vision platform. We obtained testicular tissues for 275 patients and were able to use haematoxylin and eosin (H&E)-stained glass microscope slides from 264 patients. In addition, we cut out of parts of the histopathology images (5.0 × 5.0 cm) for expansion of Johnsen’s characteristic areas with seminiferous tubules. We defined four labels: Johnsen score 1–3, 4–5, 6–7, and 8–10 to distinguish Johnsen scores in clinical practice. All images were uploaded to the Google Cloud AutoML Vision platform. We obtained a dataset of 7155 images at magnification 400× and a dataset of 9822 expansion images for the 5.0 × 5.0 cm cutouts. For the 400× magnification image dataset, the average precision (positive predictive value) of the algorithm was 82.6%, precision was 80.31%, and recall was 60.96%. For the expansion image dataset (5.0 × 5.0 cm), the average precision was 99.5%, precision was 96.29%, and recall was 96.23%. This is the first report of an AI-based algorithm for predicting Johnsen scores.
A theoretical study on the electronic, structural and optical properties of armchair, zigzag and chiral silicon–germanium nanotubes
Authors: Herrera-Carbajal Alejandro , Rodríguez-Lugo Ventura , Hernández-Ávila Juan , Sánchez-Castillo Ariadna
Published: May 2021

Infinite size silicon–germanium alloy nanotubes of several types, armchair, zigzag and chiral, are studied by theoretical analysis based on density functional theory as implemented in the SIESTA code.
Comparative study for machine learning classifier recommendation to predict political affiliation based on online reviews
Authors: Ullah Hayat , Ahmad Bashir , Sana Iqra , Sattar Anum , Khan Aurangzeb , Akbar Saima , Asghar Muhammad Zubair
Published: May 2021

In the current era of social media, different platforms such as Twitter and Facebook have frequently been used by leaders and the followers of political parties to participate in political events, campaigns, and elections. The acquisition, analysis, and presentation of such content have received considerable attention from opinion‐mining researchers. For this purpose, different supervised and unsupervised techniques have been used. However, they have produced less efficient results, which need to be improved by incorporating additional classifiers with the extended data sets. The authors investigate different supervised machine learning classifiers for classifying the political affiliations of users. For this purpose, a data set of political reviews is acquired from Twitter and annotated with different polarity classes. After pre‐processing, different machine learning classifiers like K‐nearest neighbor, naïve Bayes, support vector machine, extreme gradient boosting, and others, are applied. Experimental results illustrate that support vector machine and extreme gradient boosting have shown promising results for predicting political affiliations.
Beamforming design for MIMO full‐duplex SWIPT IoT system under imperfect CSI
Authors: Liu Dan , Zhong Ling , Xu Zhiguo , Wen Zhigang , Zou Junwei
Published: May 2021

This paper proposes a multiple‐input multiple‐output full‐duplex relay Internet of Things system under imperfect channel state information, where the relay uses time switching relaying protocol to harvest energy. Particularly, due to the uncertainty channel circumstance, the self‐interference in full‐duplex relay cannot be eliminated completely. For such a system, a joint source‐relay beamforming optimization problem which maximizes the system achievable rate subject to the transmit power and harvested energy constraints is studied. In light of the intractability of the problem, a singular value decomposition based geometric programming algorithm is investigated. The considered problem is reformulated to a diagonalized form by using singular value decomposition method. Then, the geometric programming algorithm is adopted to obtain the optimal solution for the reformulated problem. Numerical results validate the effectiveness and superiority of the proposed optimization scheme.
Inter‐numerology interference in OFDM‐IM systems
Authors: Dogan‐Tusha Seda , Tusha Armed , Basar Ertugrul , Althunibat Saud , Qaraqe Khalid , Arslan Hüseyin
Published: May 2021

In 5G and beyond communication systems, distinct numerologies can coexist to serve diverse requirements for users and applications. However, the inter‐numerology interference (INI) is a main challenge that significantly impacts the system performance. Therefore, the performance under INI has become an essential evaluation metric for the suitability of the different transmission schemes in the future communication systems. This paper analyzes the impact of INI on the performance of orthogonal frequency division multiplexing with index modulation (OFDM‐IM) systems. Specifically, an analytical expression of the INI level in OFDM‐IM systems is presented as a function of the subcarrier activation ratio (SAR) and subcarrier activation probability (SAP). Furthermore, aiming at reducing the INI level, an adaptive subcarrier mapping scheme (SMS) is proposed based on the conventional combinatorial mapping scheme. Moreover, analysis and evaluation of SAR and SAP are performed regarding the requirements of 5G and beyond services. It is proved that the INI level in OFDM‐IM systems is highly dependent not only on the number of active subcarriers but also on their position in an OFDM block.
Design and realization of ultra‐wideband absorber from C to K band
Authors: Li Yi , Xiang Zheng , Ren Peng , Feng Lijing
Published: May 2021

Here, a novel design of absorber loading dual‐layer frequency selective surfaces (FSSs) in the Salisbury screen is proposed. The design of frequency selective surfaces is mainly composed of cross‐dipole and dual‐loop metal patch. Simulation results show that this absorbing structure can achieve ultra‐wideband absorption from C band to K band and the fractional bandwidth reaches 117.1% below –10 dB. The thickness of the proposed absorbing structure is 0.078 λL and the unit cell size is 0.262 λL, where λL is the wavelength of the lowest absorbing frequency. Moreover, it shows excellent polarization stability in TE and TM modes, and it has great angular stability. Finally, the prototype of this structure is fabricated, and the measured results are in good agreement with the simulation results.
Analytical system frequency response model with virtual synchronous wind turbines
Authors: Malekpour Mostafa , Kiyoumarsi Arash , Gholipour Mehdi
Published: May 2021

The present paper devises a second‐order system frequency response (SFR) model for power systems integrating virtual synchronous variable speed wind turbines (VSWTs). The inertial response model of full converter VSWTs, in which grid‐side converters are controlled using a virtual synchronous generator concept, is developed. The derived model is incorporated into the traditional SFR model deployed to estimate the frequency behaviour of the synchronous generators following infeed loss contingencies. The proposed SFR model formulates interaction between the VSWTs rotor speed reduction and the system frequency drop. The system loads inertia is also included in the SFR model. Additionally, an analytical approach to derive the suggested SFR model for the large power system including VSWTs with different capacities and operating points is presented. Solving the proposed model gives the analytical functions for estimating deviations in the system frequency as well as VSWTs rotor speed variations. Finally, the accuracy of the devised SFR model is verified through the time‐domain simulations of a modified IEEE 39‐bus system. Particularly, impact of the VSWTs virtual inertia on the efficiency of the proposed SFR model is studied.
Synchronous machine performance under geomagnetic disturbances
Authors: Boguslawsky Ilja , Korovkin Nikolay , Popov Victor , Sokolova Olga
Published: May 2021

Geomagnetic disturbances (GMDs) are known to disturb power system equipment performance. The danger is associated with geomagnetically induced currents (GICs) occurring at the Earth's surface during GMD. GICs do not endanger power system operation conditions by themselves. The main challenge posed by GICs to power system states is the change in power system equipment operation conditions provoked by GIC flow. The primary avenue of blackout caused by GMDs is through power transformers. This, in turn, can impair the operation of other power system equipment such as synchronous machines. Modern powerful synchronous machines are not designed and engineered to cope with the negative impacts of GMDs. Moreover, the actual legal norms are inadequate in this case. Enhancing the grid's resiliency to such an event is highly interesting to the industry. The physical processes in synchronous machine windings triggered by GICs and limitations brought to power grid operations are described. First, the idea of the impact of GMDs on the power grid operation is described. The analysis of the impact of GMDs on synchronous machines is performed in the second section. In the end, the power system response under GMDs is studied.
A deep network with analogous self‐attention for short‐term traffic flow prediction
Authors: Zhang Zhao , Jiao Xiaohong
Published: May 2021

Short‐term traffic flow prediction plays a crucial role in research and application of intelligent transportation system. Neural network algorithm can use the big data for training and has more advantages over other prediction models in traffic features extraction. However, it is still a problem to extract the spatiotemporal features of traffic flow in a simple and sufficient way to improve the prediction accuracy. In this paper, a double‐branch deep residual gated convolutional neural network (RGCNN) is proposed to extract features from both time and space based on three‐dimensional traffic data, and scaled exponential linear units is used as an activation function to enhance the convergence effect of network training. In order to increase the ability of the network to fit the traffic data, an analogous self‐attention (ASA) is designed, which retains the advantages of attention while hardly increasing training costs. Simulation experiments are carried out in real traffic data sets, the simulation results of traffic flow prediction tasks in different prediction horizons show that the prediction performance of the proposed prediction model (ASA‐RGCNN) is superior to that of other common prediction models and the proposed model can be applied to the predicting task under different traffic conditions. By visualising ASA weights at different traffic flow levels, the impact of space‐time traffic data on the prediction task can also be found out.
Multi‐objective optimization of cordon sanitaire with vehicle waiting time constraint
Authors: Lin Hongzhi
Published: May 2021

The outbreak of COVID‐19 has disrupted our regular life. Many local authorities have enforced a cordon sanitaire for the protection of sensitive areas. Travelers can only travel across the cordon after getting qualified. This paper aims to propose a method to determine the optimal deployment of cordon sanitaire in terms of the number of parallel checkpoints at each entry link. A bi‐level multi‐objective programming model is formulated where the lower‐level is the transportation system equilibrium with queueing to predict link traffic flow, and the upper‐level is queueing network optimization that is a multi‐objective integer non‐linear programming. The primary objective is to minimize the total operation cost of checkpoints with a predetermined waiting time constraint and the secondary objective is to minimize system total travel time. A heuristic algorithm is designed to solve the proposed bi‐level model where the method of successive averages is adopted for the lower‐level model, and a hybrid genetic algorithm is designed for the upper‐level model. An experimental study is conducted to demonstrate the effectiveness of the proposed methods. The results show that the methods can find a good heuristic optimal solution. These methods are useful for operators to determine the optimal deployment of cordon sanitaire.
Morphology regulation of nanowire forests for tumour‐cell behaviours
Authors: Liu Yang , Kong Jinlong , Cheng Jie , Huang Chengjun , Wang Kaiqun , Chen Dapeng , Mao Haiyang
Published: May 2021

Three‐dimensional nanowire arrays based on different biomaterials have emerged as promising platforms for the studies of cell behaviours over the years. Fabrication of nanosurfaces with complex geometries and controllable morphologies is still a challenge. In this work, nanowire forests (NWFs), which exhibited various aspect ratios, were fabricated using a reactive ion etching technique. Especially, by regulating bombardment periods of oxygen and argon plasma, the aspect ratio of nanowires in NWFs could be decreased from 29:1 to 7:1. Based on superhydrophilicity of the NWFs, the interaction between the NWFs with various aspect ratios and HeLa cells (human cervical carcinoma cell line) after different culturing periods was systematically investigated. NWFs with a low aspect ratio provide appropriate nanosubstrates for the cells, enabling them to grow on and adhere to the surface. NWFs with a high aspect ratio exhibited low mechanical strength under initial cell adhesion, which further hindered cell growth and migration as the incubation time increased. These findings provide essential guidance in designing nanostructure geometries for more efficient capture of circulating tumour cells and manipulation of cytomorphology in future.
Distributed deep reinforcement learning for optimal voltage control of PEMFC
Authors: Li Jiawen , Yu Tao
Published: May 2021

Proton exchange membrane fuel cells (PEMFCs) are promising components in the renewable energy field due to their high energy efficiency and low pollution output. However, these cells are also characterized by considerable nonlinearity, which in turn adversely affects the PEMFC output voltage. Conventional control algorithms cannot guarantee sufficient output voltage control, as they lack the robust adaptive ability required for adapting to these fluctuations in PEMFCs. In this paper, an optimal output voltage controller based on distributed deep reinforcement learning, which controls the output voltage by regulating the fuel input of the PEMFC, is proposed. In addition, an ensemble intelligence exploration multi‐delay deep deterministic policy gradient (EIM‐DDPG) algorithm is proposed for this controller. An ensemble intelligence exploration policy plus a classification experience replay mechanism are included within the EIM‐DDPG algorithm to improve the exploration ability of the algorithm and thus increase the robustness and adaptive capability of the controller. As a result, the model‐free optimal output voltage controller offers high robustness and adaptability. The simulation results in this paper demonstrate that the proposed optimal controller can realize the effective control of PEMFC output voltage.
Prescribed fire and fire suppression operations influence wildfire severity under severe weather in Lassen Volcanic National Park, California, USA
Authors: Harris Lucas B. , Drury Stacy A. , Farris Calvin A. , Taylor Alan H.
Published: May 2021

Fuels treatments and fire suppression operations during a fire are the two management influences on wildfire severity, yet their influence is rarely quantified in landscape-scale analyses. We leveraged a combination of datasets including custom canopy fuel layers and post-fire field data to analyse drivers of fire severity in a large wildfire in the southern Cascade Range, California, USA. We used a statistical model of tree basal area loss from the fire, factoring in weather, fuels and terrain to quantify the extent to which prescribed burning mitigated wildfire severity by simulating potential wildfire severity without prescribed fire and comparing that with modelled severity from areas burned with prescribed fire. Similarly, using a map of operations intensity, we calculated predicted fire severity under a scenario with no operations and used these predictions to quantify the influence of operations. We found that prescribed fires and operations reduced tree basal area loss from the wildfire by an average of 32% and 22% respectively, and that severity was reduced by 72% in areas with both prescribed fire and operations. Our approach could be applied to other wildfires and regions to better understand the effects of fuel treatments and fire suppression operations on wildfire severity.
Geographic frequency and ecological correlates of juvenile colour polymorphism in green pythons (
Authors: Natusch Daniel J. D. , Lyons Jessica A.
Published: May 2021

Colour polymorphisms are common in nature, but their evolutionary significance and the mechanisms maintaining them sometimes remain poorly understood. Polymorphic green pythons (Morelia azurea and Morelia viridis) are born either red or yellow. Several processes are proposed to maintain such polymorphisms, and the assumption that colour is adaptive predicts that it may be correlated with a series of life-history and/or ecological traits. We examined 1090 green pythons from northern Australia and New Guinea and reveal strong geographic variation in the frequency of juvenile polymorphism. Some variation is explained by known genetic structure among populations, while stochastic processes (e.g. bottlenecks, founder effects) likely explain remaining variation. The yellow juvenile morph occurs in all populations of M. azurea and M. viridis, whereas the red morph occurs only in some populations of M. azurea and at varying frequencies. Yellow and red juveniles did not differ in morph-specific survival, sex ratios, morphology (tail length, head shape and mass) or diet. We discuss our results in relation to several hypotheses relating to maintenance of colour polymorphisms in nature. Although inconclusive, we are reluctant to suggest that colour is non-adaptive, and encourage additional experimental field research on the significance of polymorphism in these taxa.
Microstructural characterization and functional performance of Ni54Mn25Ga21-xDyx high-temperature shape memory alloys
Authors: Tong W. , Peng L.M.
Published: May 2021

The present study investigated the influences of Dy-addition on the microstructural characterization, functional behaviour and deformation mechanisms in high-temperature Ni54Mn25Ga21 alloys. The results indicated that adequate Dy-addition contributed to a desirable trade-off among compressive strength, ductility and functional performance. Ni54Mn25Ga20.9Dy0.1 alloy showed the highest shape memory recoverable strain due to the improvement of mechanical properties and formation of small Dy-rich precipitates. Meanwhile, an obvious pseudoelasticity was observed over a wide temperature range with a maximum recoverable strain of 3.74% at 320°C in this alloy. All the Dy-containing alloys exhibited low thermal hysteresis. However, it was revealed that an abnormal relationship between thermal hysteresis and middle eigenvalue [Formula: see text] existed for the investigated alloys with a lattice transition from cubic to tetragonal.
During the COVID-19 pandemic in Finland, the number of minor lower limb amputations decreased, whereas major amputations increased
Authors: Vuorlaakso M. A. , Uimonen M. M. , Kuitunen I. M. , Ponkilainen V. T. , Mattila V. M.
Published: May 2021

During the COVID-19 lockdown in Finland, the number of minor amputations decreased whereas transtibial amputations increased. This was an indication of delayed access to treatment leading to higher amputation. Transfemoral amputations decreased during 2020, which may be linked to higher mortality.
On the Hardness of Sparsely Learning Parity with Noise
Authors: Yan Di , Liu Hanlin , Zhao Shuoyao , Yu Yu
Published: May 2021

The Learning Parity with Noise (LPN) problem represents the average-case analogue of the NP-Complete problem “decoding linear codes”, and it has been extensively studied in learning theory, coding theory and cryptography with applications to quantum-resistant cryptographic schemes. However, LPN also suffers from large public key size which is the common drawback that hinders code-based cryptography from being practical. In this paper, we study a sparse variant of LPN whose public matrix consists of sparse vectors instead of following uniform distribution. We show a win–win argument that at least one of the following assumption is true: (i) either the hardness of sparse LPN is implied by that of the standard LPN under the same noise rate; (ii) or there exists new black-box constructions of public-key encryption schemes and oblivious transfer protocols from standard LPN. Since the second assumption relies on the infeasible noise regimes for LPN-based public-key cryptography, we believe that the first assumption is more likely to hold, i.e. sparse LPN is as hard as standard LPN. Finally, we give a (heuristic) method to further compress the sparse public matrix by evaluating pseudorandom functions with keys made public, whose security again resorts to the aforementioned win–win technique.
DCAF: Dynamic Cross-Chain Anchoring Framework using Smart Contracts
Authors: Wang Weidong , Li Xiaofeng , Zhao He
Published: May 2021

Blockchain has attracted tremendous attention from both the academia and the capital market. The insertion of data in a blockchain known as anchoring makes data verifiable and independently auditable and has many potential applications. The objective of this paper is to introduce a dynamic cross-chain anchoring framework for snapshotting users’ data into multiple public blockchains with the help of smart contracts. This paper starts by proposing the framework and depicting the components and workflow. Second, we design a target chain selection algorithm that combines the states of different blockchains. Using the algorithm, users can dynamically select a suitable public blockchain for anchoring tasks. Third, the virtual chain protocol is presented and achieves data anchoring orderly and integrally. Analyzation and evaluation show that the framework can enhance user experience, robustness and performance.