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Ultrasound velocimetry has been widely used for blood flow imaging. However, the flow measurements are constrained to resolve the in‐plane 2D flow components when using a 1D transducer array. In this work, an ultrasound speckle decorrelation analysis‐based velocimetry (3C‐vUS) is proposed for 3D velocity components measurement using a 1D transducer array. The 3C‐vUS theory is first derived and validated with numerical simulations and phantom experiments. The in vivo testing results show that 3C‐vUS can accurately measure the blood flow 3D‐velocity‐components of the human carotid artery at arbitrary probe‐to‐vessel angles throughout the cardiac cycle. With such capability, the 3C‐vUS will alleviate the requirement of operators and promote disease screening for blood flow‐related disorders. [ABSTRACT FROM AUTHOR]

Intonation is the melody and soul of speech, and plays an important role in oral communication. Nevertheless, the acquisition of English intonation by Chinese EFL learners is far from being satisfactory. It is found by empirical study that the main problems existing in acquiring English rising tone are improper placement of nucleus stress, failure to control the contour of pitch of nucleus, replacement of rising tone by falling one, epenthesis of extra central vowel after the consonant with which the nucleus or tail ends. The acquisition of rising tone is influenced by lack of intonation knowledge, poor acquisition of stress, differences between English and Chinese tone patterns, etc. One key solution is to imbue the learners with knowledge of intonation by utilizing modern phonological technologies to make possible the multimodal phonological acquisition of intonation so as to improve the learners' ability of perceiving and producing rising tone.

In this paper, we explored the combination of seismic station data and ground motion prediction equations (GMPE) to predict seismic intensity results by using Bayesian Maximum Entropy (BME) method. The results indicate that: 1) In earthquake analysis in Japan, soft data has predicted higher values of intensity in disaster areas. BME corrected this phenomenon, especially near the epicenter. Meanwhile, for earthquakes in the United States, BME corrected the erroneous prediction of rupture direction using soft data. 2) Compared with other spatial interpolation methods, the profile results of Japan earthquake and Turkey earthquake show that BME is more consistent with ShakeMap results than IDW and Kriging. Moreover, IDW has a low intensity anomaly zone. 3) The BME method overcomes the phenomenon that the strength evaluation results do not match the actual failure situation when the moment magnitude is small. It more accurately delineates the scope of the disaster area and enriches the post-earthquake processing of disaster area information and data. BME has a wide range of applicability, and it can still be effectively used for interpolation analysis when there is only soft data or few sites with data available. [ABSTRACT FROM AUTHOR]

Based on the work of Mumby et al. [Thresholds and the resilience of Caribbean coral reefs, Nature 450 (2007) 98–101], this study is devoted to investigate the deterministic and stochastic features of a coral reef ecosystem in which macroalgae and coral compete to occupy algae turfs, and the macroalgae are grazed by parrotfish. By taking the grazing rate as the focused parameter, we completely analyze the global dynamics of the deterministic coral reef ecosystem, including bistable phenomenon, linear equilibria and degenerate attractor. It is found that for different grazing rates, the coral reef system may exhibit rich dynamics which are closely dependent on the initial values. Furthermore, we derive a stochastic coral reef model in the form of continuous-time Markov chain (CTMC), and estimate the extinction probabilities of macroalgae and coral by using the branching process theory. Analytical results reveal that the macroalgae or coral species will go to extinction in a positive probability, even if it can survive in the deterministic environment. [ABSTRACT FROM AUTHOR]

With the development of display technology, people's needs for long lifetime are getting higher and higher. Due to the long development period of organic materials, how to improve the lifetime in certain organic materials system becomes more and more important. In this paper, we achieve this by varying the ratio of nitrogen and oxygen, as well as changing the power of plasma, thereby improving the performance of mobile displays. [ABSTRACT FROM AUTHOR]

A microwave photonic frequency-doubling phase shifter with a broad bandwidth and large tuning range is proposed in this paper. Frequency doubling and phase shifting are realized by processing the input microwave signal in the optical domain at a dual-drive dual-parallel Mach–Zehnder modulator (DD-DPMZM) and a dual-parallel Mach–Zehnder modulator (DPMZM). The input signal is split into two branches through a 90-degree hybrid splitter. One signal is sent to the DD-DPMZM to achieve a phase-shifted carrier-suppressed up-sideband by tuning the bias voltage, and the other is sent to the DPMZM to realize a carrier-suppressed down-sideband. By beating the phase-shifted up-sideband and the down-sideband at a photodetector (PD), the input signal is frequency doubled and phase shifted. The proposed frequency-doubling phase shifter is simulated. The results show that the frequency-doubled signal has a phase-tuning range from 0 to 360 degrees. In addition, the influence of the amplitude and phase unbalance of the 90-degree hybrid splitter on the magnitude variation and phase deviation of the frequency-doubling phase shifter is studied. [ABSTRACT FROM AUTHOR]

With the rapid development of the construction industry, there have been an uncountable number of damages caused by safety accidents at construction sites. Traditional safety management methods are no longer able to meet the needs of production. This paper presents the concept of constructing safety management scenarios for construction engineering sites. Using a production base project as a research case, it analyzes the natural and human factors involved in constructing spatial–temporal scenarios at construction sites. By employing a spatial–temporal overlay method to analyze multiple safety assessment indicators, a spatial–temporal safety management scenario for the production base project is established. Subsequently, BIM and GIS technologies are applied to perform a spatial–temporal simulation of the construction site safety management scenario. This process delineates safety and hazard areas across different construction phases based on time and spatial dimensions, enabling a comprehensive safety assessment of the construction site of the production base project. The study offers a reference and guidance for improving the level of safety management at construction project sites. [ABSTRACT FROM AUTHOR]

Accurate and rapid assessment of seismic intensity after a destructive earthquake is essential for efficient early emergency response. We proposed an improved method, AL-SM99, to assess seismic intensity by analyzing aftershock sequences that occur within 2 h of mainshocks. The implementation effect and application conditions of this method were illustrated using 27 earthquakes with Mw 6.5–8.3 that occurred globally between 2000 and 2023. When the fault system in the seismic region is clear and simple, the robust LOWESS-fitted (locally weighted regression program) curves could be used to estimate the location and length of the fault rupture. LOWESS results can indicate the overall rupture trend and make reliable rupture-scale judgments even when the fault system is complex. When Mw ≥ 7.0 and the number of aftershocks exceeds 40, the AL-SM99 intensity evaluation results may be more reliable. Using aftershock catalogues obtained by conventional means allows for a stable assessment of seismic intensities within 1.5 h of the mainshock. When the number of aftershocks is sufficiently large, the intensity assessment time can be greatly reduced. With early accessible aftershocks, we can quickly determine the rupture fault planes and have a better estimate of the seismic intensities. The results of the intensity assessment provide a useful guide for determining the extent of the hardest-hit areas. By expanding the data sources for seismic intensity assessment, the early accessible data are utilized adequately. This study provides a valuable reference point for investigating the relationship between early aftershock events and fault rupture. [ABSTRACT FROM AUTHOR]

The adsorption and hydrogenation of carbon dioxide on γ-Al2O3(110) surface-supported copper clusters of different sizes are investigated using density functional theory calculations. Our results show that the activation of CO2 is most obvious at the Cu/γ-Al2O3 interface containing the size-selected Cu4 cluster. It is interesting that the CO2 activation is more pronounced at the partially hydroxyl-covered interface. The catalytic mechanisms of CO2 conversion to methanol at the dry and hydroxylated Cu4/γ-Al2O3 interfaces via the formate route and the pathway initiated through the hydrogenation of carbon monoxide produced by the reverse water–gas shift reaction are further explored. On both interfaces, the formate pathway is identified as the preferred reaction pathway, in which the hydrogenation of HCOO to H2COO is the rate-limiting step (RLS). However, since the surface OH group can act as a hydrogen source in some elementary reactions, unlike the dry surface, the production of H2COOH species along the formate pathway is found at the hydroxylated interface. In addition, the introduction of OH at the interface leads to an increase in the kinetic barrier of the RLS, indicating that surface hydroxylation has a negative effect on the catalytic activity of CO2 conversion to CH3OH at the Cu/γ-Al2O3 interface. [ABSTRACT FROM AUTHOR]

Density functional theory calculations have been performed to study the reaction mechanism of N2 thermal reduction (N2TR) over a single metal atom incorporated nitrogen-doped graphene. Our results reveal that the type of metal atoms and their coordination environments have a significant effect on the catalytic activity of N2TR. Regarding CoN4- and FeN4-embedded graphene sheets that the metal atom is fourfold coordinated, they are inactive for N2TR owing to the poor stability of the adsorbed H2 and N2 molecules. In contrast, if the monodisperse metal atom is surrounded by three N atoms, namely, CoN3/G and FeN3/G show activity toward N2TR, and catalytic conversion of N2 into ammonia is achieved through the associative mechanism rather than the dissociative mechanism. Further investigations show that the synthesis of NH3 over the two surfaces is mainly through the formation of an NHNH* intermediate; however, the detailed reaction mechanisms are sensitive to the type of metal atom introduced into N-doped graphene. Based on the calculated kinetic barriers, FeN3/G exhibits a better catalytic activity for N2TR. The superior performance of FeN3/G can be attributed to the fact that this surface prefers a high spin-polarized state during the whole process of N2TR, while the non-spin polarized state is predicted as the ground state for most of the elementary steps of N2-fixation over CoN3/G. The present study provides theoretical insights into developing graphene-based single atom catalysts with a high activity toward ammonia synthesis through N2TR. [ABSTRACT FROM AUTHOR]