The Ura uplift section in southern Middle Siberia is one of the key sections for testing of climatic changes and evolutionary events of the Ediacaran, as well as the development of the stratigraphic ...framework for this period. The low latitude glacial deposits, positive δ13C anomalies and the Ediacaran Complex Acanthomorph-dominated Palynoflora are observed in the Dal‘naya Taiga Group succession, which occurs in the lower part of this section. The “Shuram-Wonoka” negative δ13C anomaly is recorded in the overlying Zhuya Group. We selected three horizons of highly Sr-enriched limestones in the Dal'nyaya Taiga Group for Pb-Pb isochron dating. The obtained ages (613 ± 56 Ma 581 ± 16 Ma and 575 ± 20 Ma) are the first geochronological confirmation of the Ediacaran age of the Dal‘nyaya Taiga postglacial deposits and provide a restriction for the timing of δ13C anomalies and diversification of acanthomorph acritarchs in Siberia.
•Discrimination between fossils and problematica is based on the criterium biogenicity.•Miaohe-type Macrofossils appear in mid-Ediacaran strata.•Large colonies of macroalgae covered sea-floor beneath ...wave-base.
The pseudofossils, problematica and actual macrofossils from the Middle Ediacaran Ura Formation of the Patom Basin of Siberia are critically reviewed. Both the pseudofossils and problematica are flat-clasts of ooid grainstones that are interpreted as a product of submarine gravitational or storm-induced erosional episodic events. Some extremely flat batten-shaped ooid and cementstones 2D-clasts closely resemble shreds of ribbon-like macrophyte phytoleims randomly scattered on a bedding plane. They can potentially be considered as a cement-incrustation along the algae thalli buried within ooid sands or shales, however, there is no certainty in their taxonomic identification. At the same time, other abiotic or microbially induced formation mechanisms of these fragments cannot be excluded. The Ura macrofossils, similar in size to the 2D-clasts, are described from the same outcrop, approximately 60 m downsection. They are represented mainly by the ribbon-shaped carbonaceous compressions of Liulingjitaenia alloplecta that demonstrate the stratigraphically lowest appearance of the Miaohe-type fossils in mid-Ediacaran (pre-Shuram, 580–570 Ma) strata of Ura Formation in close association with Doushantuo-type acanthomorphic acritarchs. These fossils are present as a detrital component or as in situ buried large (decimeter scale) colonial clusters. The colonies covered significant surface areas of the soft muddy sea-floor beneath wave-base. L. alloplecta themselves, commonly attributed to green macroalgae, could also be considered as composite colonies of filamentous microalgae or cyanobacteria.
This letter studies omnidirectional beamforming based on a uniform rectangular array (URA) for common message broadcasting. Noticing a subtle yet important fact that the whole (θ,φ)-angular domain ...maps to a circular region in the (u,v)-domain, we propose to optimize the beamforming weights to make the power radiation as even as possible only in the circle. The resultant scheme, termed as quasi-omnidirectional beamforming (quasi-OBF), yields near-omnidirectional radiation while the peak-to-average power ratio (PAPR) of the array elements is significantly lower than the state-of-the-art approach, which can help improve the energy efficiency of the power amplifiers (PAs) driving the antenna array. We also prove that even constraining the beamforming weights to be unimodular for maximizing the energy efficiency of the PAs, the omnidirectional beamforming is asymptotically achievable by convergence in L2 as the number of the URA elements increases to infinity. The theoretical results are corroborated by the numerical simulations.
•Optimizing within a circular frequency domain of URA achieves flatter beampattern.•Unimodular weights can achieve asymptotically omnidirectional beampattern.•More antennas facilitate flatter beampatterns.
•We create a general array signal model under a mixture of circular and strictly noncircular signals for uniform rectangular array (URA).•A computationally effective ESPRIT-like method is proposed to ...estimate automatically paired the 2-D DOAs of mixed sources by joint diagonalization.•The proposed method can solve the angle ambiguity problem when multiple incoming signals have the same azimuth or elevation angles.•The theoretical error performance as well as the deterministic Cramer-Rao bound (CRB) is analyzed.
In this paper, a two-dimensional (2-D) direction-of-arrival (DOA) estimation method for a mixture of circular and strictly noncircular signals is presented based on a uniform rectangular array (URA). We first formulate a new 2-D array model for such a mixture of signals, and then utilize the observed data coupled with its conjugate counterparts to construct a new data vector and its associated covariance matrix for DOA estimation. By exploiting the second-order non-circularity of incoming signals, a computationally effective ESPRIT-like method is adopted to estimate the 2-D DOAs of mixed sources which are automatically paired by joint diagonalization of two direction matrices. One particular advantage of the proposed method is that it can solve the angle ambiguity problem when multiple incoming signals have the same angle θ or β. Furthermore, the theoretical error performance of the proposed method is analyzed and a closed-form expression for the deterministic Cramer-Rao bound (CRB) for the considered signal scenario is derived. Simulation results are provided to verify the effectiveness of the proposed method.
The consortia for the "multi-tasked worker" model for the development of human resources in university research administrator (URA) has started from 2014 by the financial support provided by MEXT. ...This consortia attempts to develop human resources in URA who engages in cross-sector partnership. This educational program is designed by breaking vocational abilities for cross-sector partnership into component. Through this educational work, it is proved that activity of relation adjustment in different sectors contribute the achievement of URA.
Large amounts of radiocesium were released into marine environments following the Fukushima Daiichi Nuclear Power Plant accident in March 2011. Released radiocesium influenced not only marine ...environment but also marine biota in Fukushima. Since marine biota as fisheries products is important for Japanese market, it is important to assess the distribution of radiocesium in coastal environment off Fukushima for safety concerns of radioactive contamination. Radiocesium concentrations in sediments are important for understanding fishing ground conditions and for proving the safety of fisheries products in Fukushima. In this study, monthly monitoring data collected from May 2011 to March 2020 were analyzed to describe the temporal variability of 137Cs concentrations in coastal sediments off Fukushima (total of 3647 samples from eight lines at depths of 7–125 m off Fukushima, and three sites in Matsukawa-ura Lagoon). The 137Cs concentration in sediment showed a decreasing trend, but our nonlinear model fitting suggested that this rate of decrease had slowed down. Additionally, 137Cs concentrations were up to 4.08 times greater in shallow sampling sites (7, 10, 20 m depth) following heavy rainfall events (before five months vs. after five months), such as typhoons. These observations were consistent with increasing input from particulate 137Cs fluxes from rivers and increasing dissolved 137Cs concentrations in seawater. Finally, our numerical modeling suggested that riverine 137Cs input could maintain 137Cs concentrations in coastal sediment. These results indicate that riverine 137Cs input following heavy rainfall events is the main factor for maintaining 137Cs concentrations in coastal sediments near the Fukushima Daiichi Nuclear Power Plant.
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•Recent 137Cs concentrations in coastal sediments off Fukushima were described.•Decrease in 137Cs concentration abated and was maintained around 1–100 Bq/kg-dry.•137Cs concentration in sediments increased after heavy rainfall events.•Numerical models show a large 137Cs input to coastal areas via riverine particles.
This study presents a new re-scheduling method for generating units in the form of optimal power flow (OPF) problem, considering small signal stability (SSS) constraint of power system in normal ...operation and N−1 contingency of transmission lines outage. In base case, total operation cost is minimized, considering voltage stability margin and N−1 line contingency. The SSS of system is studied by using modal analysis. In case of unstable modes in the generator(s) rotor angle, the generators scheduling should be re-dispatched. Using modal analysis and sensitivity matrix, the generators are divided into three groups: increasing power generators, decreasing power generators, and unchanged power generators. In order to increase the accuracy of re-scheduling program, two new technical and economic indexes are introduced. The output power of the candidate generators is increased/decreased based on the indexes to stabilize generator(s) with unstable rotor angle (URA). The salient feature of proposed method is its capability on stabilizing system with one or more URA generators with minimum changes in base case OPF results. The Validity of proposed method is studied on IEEE 39-bus 10-machine, and IEEE 69-bus 16-machine test systems. The obtained results verify effectiveness of proposed re-dispatch algorithm in case of single or multiple URA generator(s).
In this paper we study feedback mechanisms for unsourced random access (URA) communications. We propose an algorithm to construct feedback packets broadcasted to the users by the base station (BS) ...and a feedback packet format that allows the users to estimate their channels and infer positive or negative feedback based on the presented thresholding algorithms. We show that the proposed feedback technique leads to a substantial reduction in the packet error rates and signal-to-noise ratios (SNRs) required to support various numbers of active users. We also demonstrate that the proposed feedback imposes a much smaller complexity burden on the users compared to the feedback that acknowledges only successful or only all undecoded users. Finally, we present a theoretical analysis framework that closely matches the experimental results.
Using the array antenna theory, theoretical radiation and near-field characteristics of a uniform rectangular array (URA) for high-gain or wide-beamwidth orbital angular momentum waves have been ...rigorously studied. Closed-form weighting factors of URA elements are derived based on the Hankel transform proposed for aperture antennas. Simulated radiation patterns and near-field distributions show that a URA configuration is superior to a uniform circular array in terms of antenna gain, beamwidth, and beam-scanning capability.
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