1,721,089 research outputs found
Automatic Recognition of General LPI Radar Waveform using SSD and Supplementary Classifier
No full textFor low probability of intercept (LPI) radars, frequency-modulated and phase-modulated continuous waveforms are widely used because of their low peak power compared to that of pulse waves (PW). However, there has been a limited number of studies on recognizing continuous wave (CW) LPI radar, in spite of its importance and popularity. In this paper, in order to recognize both PW and CW LPI radar waveforms, we propose an LPI radar waveform recognition technique (LWRT) based on a single-shot multi-box detector (SSD) and a supplementary classifier. It is demonstrated with Monte Carlo simulations that the proposed LWRT achieves classification performance similar to that of the current LWRT with the highest classification performance for PW LPI radar waveforms, even without the prior condition used in existing LWRTs. For CW LPI radar waveforms, on the other hand, with the combination of the SSD and the supplementary classifier, the proposed LWRT achieves extraordinary recognition performance for all 12 LPI radar modulation schemes (i. e., BPSK, Costas, LFM, Frank, P1, P2, P3, P4, T1, T2, T3, and T4) considered in the literature.
Iridium Nanosheet Catalysts Supported on Titanium Oxide for Oxygen Evolution Reaction in Polymer Electrolyte Membrane Water Electrolysis
No full textConvergent paired electrolysis for zinc-mediated diastereoselective cinnamylation of α-amino esters
No full textA paired electrochemical method is presented for the one-pot synthesis of ?,d-unsaturated a-amino esters. The method involves the in situ generation of organozinc reagents through zinc chloride reduction on the nickel cathode and the TEMPO-mediated oxidation of amino esters on the carbon anode. The presence of an ester moiety in the amine substrate was found to be crucial for achieving high diastereoselectivity.
Introducing Iridium Nanosheet Catalysts on Titanium Oxide for Oxygen Evolution Reaction in PEMWE
No full textA visco-elastic actuator with linear gas spring and variable damping
Full text linkSeries elastic actuators (SEAs) enhance safety and robustness in robotic joints but sacrifice torque and motion bandwidth compared to rigid actuators. Variable viscoelastic actuators (VVEAs) overcome these limitations by integrating an adjustable damping element with a spring, balancing open-loop torque bandwidth with impact safety and robustness. However, most existing VVEA designs rely on mechanical springs that add significant weight. We introduce a lightweight VVEA based on a pneumatic spring design. This actuator achieves linear, offline-adjustable stiffness using antagonistic gas chambers and provides online-adjustable damping via a hydraulic throttle valve. In our design, the increasing force of one chamber is moderated by the decreasing force of the other, resulting in a measured maximal deviation of 12% from the linear model. Additionally, an elastic silicone cast bladder replaces the conventional ring-shaped piston, significantly reducing breakaway force. To evaluate its benefits over standard actuators, we applied optimal control to periodic rest-to-rest motions typical of pick-and-place tasks. Based on mean tracking error, the VVEA outperforms SEAs in 29.1% of trials and rigid actuators in 89.2% of trials. Although increasing damping improves performance, it compromises safety; our optimization study demonstrates the potential of an online variable damping setpoint to balance these trade-offs. These results suggest that VVEAs hold great promise for applications requiring rapid maneuvers and enhanced impact safety and robustness.
Pt-Cu Nanosheet Catalysts for Pemfcs with Enhanced Durability through Galvanic Replacement Reaction
No full text<jats:p> In order to cope with the cataclysmic environmental problems, PEMFCs are in the spotlight as a next-generation renewable energy utilization candidate, but the high platinum unit price used in the catalyst layer is still a sticking point. Accordingly, attempts are being made to maximize platinum utilization and improve performance through shape control of the catalyst, but there is a problem in that the structure collapses under extreme PEMFCs driving conditions and the performance deteriorates rapidly, resulting in wistful durability. In this work, Pt-Cu nanosheet with 15~20 nm lateral size and 1 nm thickness was synthesized on carbon support (PtCu NS/C) and further enhanced durability through surface copper substitution using galvanic replacement reaction (G-PtCu NS/C). To clarify the catalyst structure in more detail, acid-leached Pt-Cu nanosheet (A-PtCu NS/C) was synthesized by eluting copper on the surface, and the differences in electronic structure were compared through XAS and XPS. In the half-cell configuration, G-PtCu NS/C demonstrated high performance and excellent durability retention after 30,000 square-wave cycles (SWC) of accelerated stress test (AST). Moreover, G-PtCu NS/C showed marginal shift in CO adsorption peak after AST, indicating the high stability of catalyst structure. In the full-cell test, performance of G-PtCu NS/C after 30,000 SWC AST is consistent to initial performance, while PtCu NS/C showed noticeable power density drop at high current density region. Ex-situ EDS elemental mapping and XRF of membrane-electrode assembly (MEA) after AST confirms that transition metal dissolution on G-PtCu NS/C was imperceptible. Our study suggests new engineering method for shaped controlled catalysts to be applied on PEMFCs. </jats:p>
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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