Ocean‐Only FAFMIP: Understanding Regional Patterns of Ocean Heat Content and Dynamic Sea Level Change

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Microwave Synthesis and High‐Mobility Charge Transport of Carbon‐Nanotube‐in‐Perovskite Single Crystals

Organolead trihalide perovskites have emerged as a new class of competitive solution-processed semiconductors due to their unique optoelectronic properties. However, poor ambient stability and charge transport are the Achilles’ heel of hybrid perovskites, thus limiting their applications. In this work, microwave-assisted synthesis is applied for the first time to rapidly grow perovskite single crystals embedded with single-wall carbon nanotubes. These nanotube-in-perovskite single crystals are endowed with a carrier mobility one order of magnitude higher than the pure counterpart and the related photodetectors show an ultrafast photo-response speed (5 and 80 ns for rise and decay time, respectively). The fast and uniform heating of microwave irradiation facilitates the synthesis of ambient-stable crystals with nanoscale additives, paving the way to creating a wide range of mixed-dimensional perovskite-based nanocomposites with optimal properties and device performance

Influence of the Dry Friction Suspension System Characteristics on the Stick-Slip of Vertical Vibration of a Three-Piece Bogie

The dry friction structure is a commonly used vibration-damping method for railway vehicles. Insufficient vibration damping performance will cause excessive vibration of the vehicle, which is not conducive to the safety of the vehicle. However, the mechanism of vibration damping and the cause of clamping stagnation have not been well resolved. This paper uses the analytical method, numerical method, and finite element method to analyze the vertical dynamic characteristics of the simple suspension system with dry friction and demonstrates that the numerical method is an effective method to study the dry model. The conditions for the system to produce sticking events were analyzed by the numerical method. The analysis shows that the system's excitation is too small, which causes clamping stagnation to the system. The reduction of the wedge angle and the friction coefficient are conducive to eliminating sticking. A negative side frame angle is conducive to reducing the high-frequency energy of the excitation. Decreasing spring stiffness or increasing system mass to reduce system frequency can reduce sticking events. The mutual verification of different methods confirms the correctness of the analysis method and analyzes the cause of sticking or clamping stagnation from the mechanism, which provides a new idea for the design and improvement of the dry friction damping system of railway vehicle bogies

The Influences of the Atlantic Multidecadal Oscillation on the Mean Strength of the North Pacific Subtropical High during Boreal Winter

The Atlantic multidecadal oscillation (AMO) has been shown to be capable of exerting significant influences on the Pacific climate. In this study, the authors analyze reanalysis datasets and conduct forced and coupled experiments with an atmospheric general circulation model (AGCM) to explain why the winter North Pacific subtropical high strengthens and expands northwestward during the positive phase of the AMO. The results show that the tropical Atlantic warming associated with the positive AMO phase leads to a westward displacement of the Pacific Walker circulation and a cooling of the tropical Pacific Ocean, thereby inducing anomalous descending motion over the central tropical Pacific. The descending motion then excites a stationary Rossby wave pattern that extends northward to produce a nearly barotropic anticyclone over the North Pacific. A diagnosis based on the quasigeostrophic vertical velocity equation reveals that the stationary wave pattern also results in enhanced subsidence over the northeastern Pacific via the anomalous advections of vorticity and temperature. The anomalous barotropic anticyclone and the enhanced subsidence are the two mechanisms that increase the sea level pressure over the North Pacific. The latter mechanism occurs to the southeast of the former one and thus is more influential in the subtropical high region. Both mechanisms can be produced in forced and coupled AGCMs but are displaced northward as a result of stationary wave patterns that differ from those observed. This explains why the model-simulated North Pacific sea level pressure responses to the AMO tend to be biased northward

Distinguishing the Quasi-Decadal and Multidecadal Sea Level and Climate Variations in the Pacific: Implications for the ENSO-Like Low-Frequency Variability

Low-frequency sea level variations with periods longer than interannual time scales have been receiving much attention recently, with the aim of distinguishing the anthropogenic regional sea level change signal from the natural fluctuations. Based on the available sea level products, this study finds that the dominant low-frequency sea level mode in the Pacific basin has both quasi-decadal variations and a multidecadal trend reversal in the early 1990s. The dominant sea level modes on these two time scales have different tropical structures: a west-east seesaw in the tropical Pacific on the multidecadal time scale and a dipole between the western and central tropical Pacific on the quasi-decadal time scale. These two sea level modes in the Pacific basin are closely related to the ENSO-like low-frequency climate variability on respective time scales but feature distinct surface wind forcing patterns and subbasin climate processes. The multidecadal sea level mode is associated with the Pacific decadal oscillation (PDO) and Aleutian low variations in the North Pacific and tropical Pacific sea surface temperature anomalies toward the eastern basin, while the quasi-decadal sea level mode is accompanied by tropical Pacific sea surface temperature anomalies centered in the central basin along with the North Pacific part, which resembles the North Pacific Oscillation (NPO) and its oceanic expressions [i.e., the North Pacific Gyre Oscillation (NPGO) and the Victoria mode]. The authors further conclude that the ENSO-like low-frequency variability, which has dominant influences on the Pacific sea level and climate, comprises at least two distinct modes with different spatial structures on quasi-decadal and multidecadal time scales, respectively

Research into Carbon Dioxide Curing’s Effects on the Properties of Reactive Powder Concrete with Assembly Unit of Sulphoaluminate Cement and Ordinary Portland Cement

Excessive emissions of carbon dioxide can lead to greenhouse effect thus destroying the ecological balance. Therefore, effective measures need to be taken to reduce the emission of carbon dioxide. In this study, the influence of carbon dioxide curing on the mechanical strength and NaCl freeze-thaw deterioration of reactive powder concrete (RPC) with the assembly unit of sulphoaluminate cement and ordinary Portland cement was investigated. The ratio of sulphoaluminate cement ranged from 0% to 100% by the total mass of cement with the curing age ranging from 1 d to 28 d. The mechanical strength of RPC with 50% ordinary Portland cement and 50% sulphoaluminate cement containing the polypropylene fibers ranging from 1% to 4% by volume of RPC were investigated. Moreover, the following mass and mechanical strength loss rates, the carbonation depth, the chloride ion migration coefficient and the relative dynamic elastic modulus (RDEM) during NaCl freeze-thaw cycles were determined. Finally, the scanning electron microscope (SEM) and X-ray diffraction were applied in investigating the carbonation process of RPC. Results showed that the addition of sulphoaluminate cement could improve the mechanical strength of RPC at low curing age (lower than 7 d). However, when the cuing age reached 7 d, the sulphoaluminate cement demonstrated negative effect on the mechanical strength. Moreover, the carbon dioxide curing led to increases in the mechanical strength and when ordinary Portland cement was added the enhancing effect was more obvious. Furthermore, the carbon dioxide curing could effectively improve the resistance of NaCl freeze-thaw cycles and increase the carbonation depth. Finally, the increasing dosages of polypropylene fibers were advantageous to the mechanical strength and the resistance of NaCl freeze-thaw cycles. From the researching results of the microscopic performance, the carbon dioxide curing could improve the compactness of hydration products and reduce the content of calcium hydroxide especially at the curing age of 3 days

Climate model uncertainty and trend detection in regional sea level projections: A review

Projections of future sterodynamic sea level change from global climate models are associated with different sources of uncertainty. From a scientific, societal and policy-making perspective, it is relevant to both understand and reduce uncertainty in projections of climate change. Here, we review recent findings which describe, and shed light on, climate model uncertainty focusing particularly on two types of model uncertainty that contribute to the currently large spread in dynamical sea level patterns (i.e., regional sea level relative to the global mean). These uncertainties are: (1) intermodel uncertainty due to differences in models’ responses in a warming climate and (2) internal model variability due to an individual model’s own climate variability. On timescales longer than about 50 years from now, anthropogenic sterodynamic (dynamic plus global mean) sea level trends from middle- and high-end forcing scenarios will be larger than internal model variability. By 2100, these anthropogenic trends will also be larger than intermodel uncertainty when global mean thermosteric sea level rise and/or melting contributions from land ice are considered along with dynamic sea level changes. Furthermore, we discuss projections of future coastal sea level from the perspective of global climate models as well as from downscaled efforts based on regional climate models. Much knowledge and understanding has been achieved in the last decade from intermodel experiments and studies of sea level process-based model; here, the prospects for improving coastal sea level and reducing sea level uncertainty are discussed

Stratospheric ozone depletion and tropospheric ozone increases drive Southern Ocean interior warming

Atmospheric ozone has undergone distinct changes in the stratosphere and troposphere during the second half of the twentieth century, with depletion in the stratosphere and an increase in the troposphere. Until now, the effect of these changes on ocean heat uptake has been unclear. Here we show that both stratospheric and tropospheric ozone changes have contributed to Southern Ocean interior warming with the latter being more important. The ozone changes between 1955 and 2000 induced about 30% of the net simulated ocean heat content increase in the upper 2,000 m of the Southern Ocean, with around 60% attributed to tropospheric increases and 40% to stratospheric depletion. Moreover, these two warming contributions show distinct physical mechanisms: tropospheric ozone increases cause a subsurface warming in the Southern Ocean primarily via the deepening of isopycnals, while stratospheric ozone causes depletion via spiciness changes along isopycnals. Our results highlight that tropospheric ozone is more than an air pollutant and, as a greenhouse gas, has been pivotal to the Southern Ocean warming