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Frequency-hopping (FH) communication adversarial research is a key area in modern electronic countermeasures. To address the challenge posed by interfering parties that use deep neural networks (DNNs) to classify and identify multiple intercepted FH signals—enabling targeted interference and degrading communication performance—this paper presents a batch feature point targetless adversarial sample generation method based on the Jacobi saliency map (BPNT-JSMA). This method builds on the traditional JSMA to generate feature saliency maps, selects the top 8% of salient feature points in batches for perturbation, and increases the perturbation limit to restrict the extreme values of single-point perturbations. Experimental results in a white-box environment show that, compared with the traditional JSMA method, BPNT-JSMA not only maintains a high attack success rate but also enhances attack efficiency and improves the stealthiness of the adversarial samples. [ABSTRACT FROM AUTHOR]

Among the REBa2Cu3O7‐δ (REBCO or RE123, RE = rare earth element) family, SmBCO is preferably used in top‐seeded melt‐growth (TSMG) because of its outstanding property and more controllable stoichiometry 123. Nevertheless, the refinement of Sm2BaCuO5 (Sm211) particles has been challenging for high‐performance SmBCO bulks. Conventional precursor powders (SmBa2Cu3O7‐δ plus Sm2BaCuO5) intrinsically result in enlarging Sm2BaCuO5 particles due to their coarsening and epitaxial growth during the heating process. Here, we used modified precursor powders (MPPs, Sm2O3 plus Ba2Cu3O5) in air‐processed TSMG, in which there is neither Sm211 in the beginning nor related enlargement during heating. Consequently, the nucleation catastrophe of Sm211 occurred above the peritectic temperature, which in situ formed, possessing naturally small size. Further, aiming to suppress the Sm/Ba substitution, Ba‐rich MPP, substituting Ba2Cu3O5 with Ba3Cu4O7) was employed, producing an excellent SmBCO bulk with a diameter of 24 mm: levitation force of 51.5 N and trapped field of 0.537 T. Optical micrographs and quantitative analyses confirmed the superior refinement and distribution of Sm211 particles in SmBCO bulks. Most importantly, new strategies in this work are widely applicable for developing cost‐effective and high‐performance other REBCO bulk superconductors. [ABSTRACT FROM AUTHOR]

The innovation is the soul of one nation making progresses. To build an innovative country, we need to train more innovative talents who is capable of public administration. The innovative talents training of public administration undergraduate faces a lot of problems, such as the influences of traditional culture, the constraint of education ideology, the unclear definition of the specialty, the inconspicuous specialty features, and the weak practice teaching. On the basis of the characteristics of innovative talents, this paper tries to explore the effective approaches for training innovative talents of public administration undergraduates.

Objective: The study aimed to investigate the clinical characteristics of patients with multi-canal benign paroxysmal positional vertigo (MC-BPPV). Methods: We performed a retrospective analysis of 927 patients with BPPV who were admitted to our hospital between January 1, 2016 and December 31, 2019. The clinical data of all patients were collected. The Dix-Hallpike, straight head-hanging, and supine Roll tests were performed in all patients. The nystagmus was recorded using videonystagmography. The clinical characteristics of patients with MC-BPPV and single canal BPPV (SC-BPPV) was analyzed and compared. Results: Among 927 patients included, 49 (5.29%) patients had MC-BPPV, 878 (94.71%) patients had SC-BPPV. There were significant differences in the male to female ratio (1:3.90 vs 1:1.81, P <.05), mean age (62.47±12.51 vs 59.04±13.72, P <.05), as well as the ratio of cupulolithiasis to canalithiasis (1:1.45 vs 1:4.78, P <.01) between patients with MC-BPPV and SC-BPPV. The frequency of involvement of PC, HC, and AC were involved for 66 (67.35%), 23 (23.47%), and 9 (9.18%) times, respectively, in patients with MC-BPPV, which were involved in 581 (66.17%), 281 (32.0%), and 16 (1.82%) patients, respectively, in patients with SC-BPPV. No significant difference was found in the frequency of involvement of PC and HC between patients with MC-BPPV and SC-BPPV, while there was significant difference in the frequency of AC involvement between 2 groups (P <.01). Ipsilateral PC-HC-BPPV (n = 18) and bilateral PC-BPPV (n=19) were the most common among patients with MC-BPPV. Twenty-six (53.06%) patients had ipsilateral MC-BPPV, 23 (46.94%) had bilateral MC-BPPV. Of the 26 patients with ipsilateral MC-BPPV, 7 patients combined with unilateral peripheral vestibular disorder. Conclusion: Patients with MC-BPPV had a significantly older mean age at disease onset and a higher proportion of females compared with patients with SC-BPPV. Cupulolithiasis was more common in MC-BPPV. AC involvement was also much more common in MC-BPPV than in SC-BPPV. [ABSTRACT FROM AUTHOR]

"Social Research Methods," as a methodology course, combines theories and practices closely. Based on the synergy theory, this paper tries to establish an integrated multi-level bilingual teaching mode. Starting from the transformation of teaching concepts, we should integrate interactions, experiences, and researches together and focus on cultivating innovative and practical international talents.

In modern warfare, frequency-hopping communication serves as the primary method for battlefield information transmission, with its significance continuously growing. Fighting for the control of electromagnetic power on the battlefield has become an important factor affecting the outcome of war. As communication electronic warfare evolves, jammers employing deep neural networks (DNNs) to decode frequency-hopping communication parameters for smart jamming pose a significant threat to communicators. This paper proposes a method to generate adversarial samples of frequency-hopping communication signals using adaptive whitening and feature gradient smoothing. This method targets the DNN cognitive link of the jammer, aiming to reduce modulation recognition accuracy and counteract smart interference. First, the frequency-hopping signal is adaptively whitened. Subsequently, rich spatiotemporal features are extracted from the hidden layer after inputting the signal into the deep neural network model for gradient calculation. The signal's average feature gradient replaces the single-point gradient for iteration, enhancing anti-disturbance capabilities. Simulation results show that, compared with the existing gradient symbol attack algorithm, the attack success rate and migration rate of the adversarial samples generated by this method are greatly improved in both white box and black box scenarios. [ABSTRACT FROM AUTHOR]

REBa 2 Cu 3 O 7−δ (REBCO, RE = rare earth elements) cryomagnets have considerable potential for magnetic applications due to their high field trapping capacities over 10 T at temperatures below 77 K. The controlled nucleation of REBCO crystals for attaining superior performance decisively relies on the seeding strategy related to seed material and seeding assembly. Recently, buffer-assisted seeding approaches have been developed for reliable growth, in which buffer-crystals are by-products and discarded after splitting off from main crystals as ceramic waste though containing certain expensive matters such as RE, Ag and Pt. Here, for the first time, we succeeded in utilizing YBCO and NdBCO/Ag buffer-crystals as seeds for producing REBCO crystals under maximum processing temperatures of 1015 ℃ and 1053 ℃, respectively. YBCO specimens were characterized by differential scanning calorimetry and secondary ion mass spectrometry. It was verified that the buffer-crystal was 5.5 K higher than the normal-crystal in peritectic temperature (T p). Furthermore, the highly distributed Mg element was identified in the upper middle part of buffer-crystal, which was diffused from the Mg-involved NdBCO seed in previous fabrication. It is the Mg existence that enhanced T p of the buffer-crystal and made it highly thermal stable in seeding YBCO growth. In contrast to expensive commercial film-seeds and multistep home-prepared crystal-seeds, buffer-crystal-seeds distinctively have cost- and time-saving benefits. Most importantly, the current success adds new value of reusability to buffer-assisted seeding approaches towards a sustainable fabrication of REBCO cryomagnets. [ABSTRACT FROM AUTHOR]

The microstructure of a bulk superconductor may fundamentally affect its field trapping and levitation performance for practical applications. Recently, a modified top-seeded melt growth using only Y2O3 and Ba2Cu3Ox precursor powder combined with a layered arrangement of graded Y2O3 content was reported to significantly refine Y2BaCuO5 particles as well as their distribution. In this paper, we have evaluated and compared the trapped field of a CPP (conventional precursor powder), an MPP (modified precursor powder), and an L-MPP (layered and compositionally graded) sample magnetized by both field cooling magnetization (FCM) and pulsed field magnetization (PFM) at 77 K. The 25 mm diameter YBa2Cu3O7-δ sample made from L-MPP shows the highest trapped field of remarkably 1.01 T and an advanced in-field performance. And the trapped fields achieved via PFM are close to (>93%) that obtained by FCM for all the three samples. However, a more dramatic flux motion has been observed for the MPP and L-MPP sample during the PFM process. The resulted trapped field distribution exhibited the effect of the homogeneity of the sample on the trapped field. [ABSTRACT FROM AUTHOR]

Results are reported on tuning the electrical and optical properties of sputter-deposited vanadium dioxide (VO2) thin films through control of substrate growth temperature (Ts). As Ts increases from 550 to 700 °C, the morphology changes from granular to smooth film and finally to rough film. X-ray diffraction shows the presence of VO2 along with additional weak features related to the presence of non-stoichiometric phases. Electrical measurements show the phase transition to change from abrupt to gradual as both the below- and above-transition resistivities vary with Ts. The transition and hysteresis dependences observed in electrical resistivity are similarly observed in infrared transmission. Terahertz transmission measurements show that high conductivity above the phase transition is more important in achieving high modulation depth than obtaining high resistivity below the transition. We attribute changes in the electrical and optical properties to the formation of V and O vacancies, which result in diverse valence states from the ideal V4+ of VO2. Low Ts produces material with V5+ states resulting in higher resistivity in both the insulating and metallic phases. Alternatively, high Ts introduces material with V3+ states leading to lower resistivity in the insulating phase but slightly higher resistivity in the metallic phase. [ABSTRACT FROM AUTHOR]

NdBa2Cu3O7‐δ thin film deposited on a MgO substrate has been verified to remain solid above its peritectic melting temperature (Tp). Such a superheating nature is attributed to its low energy surface and epitaxial interface with substrate. Here, combining superheating nature with doping effect, we report a novel structure, Mg‐doped NdBa2Cu3O7‐δ film with YBa2Cu3O7‐δ buffer layer for the first time. Remarkably, this film presents a higher thermal stability level than heretofore possible when acting as a seed for preparing SmBa2Cu3O7‐δ bulks by melt growth, enduring a temperature of 1128°C, 43 K above its Tp for 1 hour. The utilization of such a high Tmax in melt growth is beneficial to the fabrication of large‐sized and high‐performance bulk in terms of effectively broadening the growth window and suppressing the heterogeneous nucleation. More importantly, some high thermal stability required technological applications, such as batch growth and failed bulk recycling, are likely to be realized by this novel Mg‐doped NdBa2Cu3O7‐δ film seed. Finally, we show how the observed metastable phase is linked to the distinctive film architecture. [ABSTRACT FROM AUTHOR]

Sizable and uniform Y1‐xCaxBa2Cu3O7‐δ single crystals are of significant importance to study high‐temperature superconductivity. However, the severe liquid loss resulting from intrinsic wetting property during top‐seeded solution‐growth (TSSG), makes it difficult to obtain such crystals. Here the reactive wetting performance of the Ca‐Y‐Ba‐Cu‐O solution on two types of crucibles was studied. It was identified that the spreading process on the Y2O3 crucible is characterized by forming double‐layer of Y2BaCuO5 and YBa2Cu3O7‐δ, while that on the CaSZ crucible (Ca‐stabilized ZrO2) produces the BaZrO3 layer with CuO phase. In the former case, the liquid has a low energy interface with the top layer of YBa2Cu3O7‐δ, leading to strong spreading and creeping behaviors. Conversely, due to a high interfacial energy between solution and BaZrO3, the CaSZ crucible has a low wettability, particularly beneficial to solve the liquid loss problem. Consequently, with negligible liquid creeping out of CaSZ crucibles, we succeeded in growing a series of homogeneous Y1‐xCaxBa2Cu3O7‐δ single crystals with an acceptable size up to a × b × c = 11.2 × 11 × 4.8 mm3. Moreover the wetting modes of solution on various kinds of crucibles for TSSG in growing doped YBa2Cu3O7‐δ single crystals were also elucidated. Most importantly, the understanding gained from this work is broadly applicable for producing other desirable doped‐crystals. [ABSTRACT FROM AUTHOR]

The Nd1+xBa2−xCu3Oy superconductor is considered to be one of the most promising materials in the REBaCu3Oy family owing to its excellent properties of high critical transition temperature (Tc) and high current density. However, the substitution of Nd on the Ba site occurs easily with this cation non-stoichiometric oxide, particularly in the ambient air, during the melt growth process, leading to a severe deterioration in the superconducting performance. Here, we combined thermodynamic with kinetic methods, namely the composition-control melt-growth (CCMG) and cooling-rate-control melt-growth (CRCMG) method, for the synthesis. We used Ba-rich precursors in the air-processed CCMG, which underwent an optimal cooling step (CRCMG) for increasing the chemical potential of Ba and tuning the oxygen vacancy during the growth. As a result, the Nd1+xBa2−xCu3Oy bulk could reach a high Tc of 95 K in air. In the peritectic reaction, it was found that the higher cooling rate reduces the absorption of oxygen during the formation of Nd1+xBa2−xCu3Oy, resulting in the reduction of the whole cation valence, and therefore, a low x value in Nd1+xBa2−xCu3Oy was gained. In addition, considering their brittle nature and discontinuous growth trend, Nd1+xBa2−xCu3Oy superconductor bulks were optimized for the growth step in a gradual acceleration cooling rate mode. As a result, the cryomagnet (16 mm in diameter) with a high Tc of 95 K and a trapped field of 0.60 T, superior to the previously reported air-processed ones, was successfully obtained. This success in the control of the cation stoichiometry and growth mode opens a promising pathway for the preparation of more functional oxides. [ABSTRACT FROM AUTHOR]

The refinement and uniformity of Y2BaCuO5 (Y211) are of vital importance in preparing large-sized YBa2Cu3O7−δ (Y123) bulks with high field trapping ability by top-seeded melt-growth (TSMG). However, the inherent enlargement and segregation of Y211 particles during the TSMG process have long puzzled researchers. Here, a novel method called L-MPP is reported, in which, instead of conventional precursor powder (CPP, Y123 plus Y211), modified precursor powder (MPP, Y2O3 plus Ba2Cu3Ox) is used to combine with a layered and compositional graded structure. Moreover, sizable Y123 bulks with a diameter of 25 mm were successfully prepared, rather than those of 16 mm reported in previous MPP work. The optical micrographs and quantitative analyses confirm that the Y211 particles in the L-MPP sample are visibly refined and better distributed simultaneously. As a result, the trapped fields of Y123 bulks significantly increase from 0.496 T of CPP to 1.01 T of L-MPP, and their levitation forces are enhanced by nearly 50% from 46.2 N of CPP to 68.3 N of L-MPP. Most importantly, this method is widely applicable for preparing other REBCO (RE = rare earth) bulk superconductors. [ABSTRACT FROM AUTHOR]

The structure, metal-insulator transition (MIT), and related Terahertz (THz) transmission characteristics of VO2 thin films obtained by sputtering deposition on c-, r-, and m-plane sapphire substrates were investigated by different techniques. On c-sapphire, monoclinic VO2 films were characterized to be epitaxial films with triple domain structure caused by β-angle mismatch. Monoclinic VO2 β angle of 122.2° and the two angles of V4+-V4+ chain deviating from the am axis of 4.4° and 4.3° are determined. On r-sapphire, tetragonal VO2 was determined to be epitaxially deposited with VO2 (011)T perpendicular to the growth direction, while the structural phase transformation into lower symmetric monoclinic phase results in [formula] and (200) orientations forming a twinned structure. VO2 on m-sapphire has several growth orientations, related with the uneven substrate surface and possible inter-diffusion between film and substrate. Measurements of the electrical properties show that the sample on r-sapphire has MIT property superior to the other two samples, with a resistivity change as large as 9 × 104 times and a transition window as narrow as 3.9 K, and it has the highest resistivity with the lowest free carrier density in the insulating phase. THz transmission measurements on VO2 films grown on r-plane sapphire substrates revealed intensity modulation depth as large as 98% over a broadband THz region, suggesting that VO2 films are ideal material candidates for THz modulation applications. [ABSTRACT FROM AUTHOR]