Foam materials with controllable pore structure prepared from nanofibrillated cellulose with addition of alcohols

Low-density foams based on nanofibrillated cellulose (NFC) made from Pinus massonianesoftwood pulp were prepared from NFC aqueous suspensions containing one of four C2–C4alcohols followed by freeze-drying, with the goal of controlling their pore structure and reducing the shrink rate. The foams prepared from NFC suspensions containing ethanol, isopropanol and n-butanol exhibited highly porous structures with a honeycomb-like cellular texture featuring well-defined “cell walls” between the layers. By contrast, the tert-butanol/NFC foam featured a higher number of smaller size pores with irregular shape. The foams prepared by freezing at −196 °C with ethanol also revealed small size pores, with no layered pore structure. The results obtained suggested that freeze-drying could be used to control the key foam parameters by adding different alcohols into an NFC suspension and adjusting the freezing temperature. Combining the obtained information, a possible formation mechanism was proposed. The microstructure, density, porosity, shrinkage, mechanical properties and thermal properties of NFC foams were determined. The obtained NFC foams feature low shrinkage upon formation and thermal conductivity. Smaller Young’s modulus and energy absorption yet similar yield stress values compared to the blank indicate that the freeze-drying in the presence of alcohols tends to generate “soft” foams

Effects of acid hydrolysis waste liquid recycle on preparation of microcrystalline cellulose

Large amounts of acidic waste are produced on the industrial scale during hydrolysis of partially amorphous cellulose to produce microcrystalline cellulose (MCC). The essential disposal and treatment of this highly acidic liquid wastes the acid feedstock and increases the production cost. To maximize the use of acid without sacrificing the MCC product quality, this project reports a successful attempt to recycle the acid hydrolysis waste liquid, focusing on the impact of waste recycling on MCC morphology and reducing sugar in the hydrolysate. The results showed that when the waste liquid is recycled 1-5 times, no metal accumulation occurred while cellulose particles remained intact, maintaining their shape and size. Their extent of crystallinity remained nearly constant, even increasing slightly with up to three cycles. The concentration of reducing sugar showed growth when recycling the waste liquid up to three times, although not quite to the levels that would allow for its cost-effective fermentation. The acid amount to be added at the start of each cycle was near 50% of that used on the first stage

The spatiotemporal characteristics and driving mechanisms of subsurface marine heatwaves in the Xisha Region

Under the background of global climate change, Subsurface Marine Heatwaves (SSMHWs) have become a ‘hot-spot’ research due to their significant impacts on marine ecosystems. Temperature data from the ECCO2 for the years 1992 to 2021 is used to research the spatiotemporal characteristics of SSMHWs in the upper 500 m over the Xisha region (110°E to 113°E, 15°N to 18°N). This study indicates that SSMHWs of high intensity occur in the Xisha area, with the vertical maximum intensity at approximately 100 m. These events exhibit significant seasonal variations, with the highest intensity occurring in May. The intensity of SSMHW in the analysis region varies interannually. SSMHWs have intensified at a rate of 1.53°C·Days/Year and tend to shift to deeper water over the past three decades. A block-based method for SSMHW identification is proposed, in order to take the vertical extent of the event in consideration. By analyzing the eight most intense events based on spatial cumulative intensity, it suggested that warm mesoscale eddies may play an important role on the spatial distribution of the SSMHWs. Statistical analysis shows that the intensity and coverage of the warm mesoscale eddy in the Xisha zone may influence the intensity and evolution of the SSMHWs. Additionally, only 18.27% of SSMHW events occur with apparent surface marine heatwave signals. These findings are vital for uncovering SSMHW dynamics in the Xisha area, and are important for future monitoring, early warnings and marine conservation

Ocean internal tides suppress tropical cyclones in the South China Sea

Tropical Cyclones (TCs) are devastating natural disasters. Analyzing four decades of global TC data, here we find that among all global TC-active basins, the South China Sea (SCS) stands out as particularly difficult ocean for TCs to intensify, despite favorable atmosphere and ocean conditions. Over the SCS, TC intensification rate and its probability for a rapid intensification (intensification by ≥ 15.4 m s−1 day−1) are only 1/2 and 1/3, respectively, of those for the rest of the world ocean. Originating from complex interplays between astronomic tides and the SCS topography, gigantic ocean internal tides interact with TC-generated oceanic near-inertial waves and induce a strong ocean cooling effect, suppressing the TC intensification. Inclusion of this interaction between internal tides and TC in operational weather prediction systems is expected to improve forecast of TC intensity in the SCS and in other regions where strong internal tides are present

Analytical Computation of Information Rate for MIMO Channels

Information rate for discrete signaling constellations is significant. However, the computational complexity makes information rate rather difficult to analyze for arbitrary fading multiple-input multiple-output (MIMO) channels. An analytical method is proposed to compute information rate, which is characterized by considerable accuracy, reasonable complexity, and concise representation. These features will improve accuracy for performance analysis with criterion of information rate

Grey Prediction Model for Drying Shrinkage of Cement Concrete Made from Recycled Coarse Aggregate Containing Superabsorbent Polymers

The aim of this paper is to investigate the effect of superabsorbent polymers (SAPs) on the drying shrinkage of the recycled concrete (RC). The natural aggregate (NA) was replaced by recycled aggregate at three replacement ratios (0%, 50%, and 100%). Then, the recycled concrete (RC) with different SAP contents was prepared. The performance of recycled concrete with different SAP content was analyzed with slump test, compressive strength test, and drying shrinkage test. GM (1, N) grey prediction model was utilized to predict the drying shrinkage of recycled concrete containing SAP. The results show that the strength and durability of concrete are decreased by the addition of recycled aggregate. With the increase of the dosage of SAP, the strength and durability also raise. The prediction GM (1, N) model for the drying shrinkage of recycled concrete with SAP is in good agreement with the actual drying shrinkage

What influences Metro station ridership in China? Insights from Nanjing

China is undertaking one of the most ambitious rail expansions in the world. This paper investigated the impacts of factors on ridership within Metro stations’ pedestrian catchment area (PCA) in Nanjing, China. Direct ridership model was developed to explain the ridership at 55 Metro stations using a Geographic Information System (GIS) and multiple regression analysis. Independent variables included factors measuring land use, external connectivity, intermodal connection, and station context. Six variables were found to be significantly associated with Metro station ridership at the 0.05 level: population, business/office floor area, CBD dummy variable, number of education buildings, entertainment venues and shop centers. Five variables were proved to be related to station ridership at the 0.01 significance level: employment, road length, feeder bus lines, bicycle park-and-ride (P&R) spaces, and transfer dummy variable. In particular, CBD dummy variable, the number of education buildings, entertainment venues and shop centers, and bicycle P&R spaces were found to be significantly connected to Metro station ridership in the present study. The results not only confirm some findings from previous studies but also show distinct differences regarding some variables specific to the Chinese context

Integration Application of 8K Ultra HD Video and DMS Audio Broadcast System

In recent years, people’s demand for audio and video playback quality has gradually increased. High definition video and high reduction audio are two important index. The 8K ultra-high-definition television broadcasting system was developed by Beijing HeXinChenGuang Information Technology Co., Ltd. It can broadcast ultra-high-definition uncompressed video signals with a bandwidth of 8GB/s and a resolution of 7680×4320. The Dynamic Matrix Sound (DMS) is a new multi-channel pickup system based on the principle of sound field optimization and the Huygens principle. DMS is developed by the Key Laboratory of Media Audio Education of the Communication University of China. This paper proposes a communication method that integrates the above two systems. It mainly describes an application layer protocol based on User Datagram Protocol (UDP). It focuses on the message distribution and message transmission mechanism of the protocol. The operating conditions can achieve synchronous playback of 8K ultra-high-definition video and DMS audio. The integration application of 8K ultra HD video and DMS audio broadcast system is realized

Multi-Scale Structural Design and Advanced Materials for Thermal Barrier Coatings with High Thermal Insulation: A Review

Thermal barrier coatings (TBCs) are a fundamental technology used in high-temperature applications to protect superalloy substrate components. However, extreme high-temperature environments present many challenges for TBCs, such as the degradation of their thermal and mechanical properties. Hence, highly insulating, long-life TBCs must be developed to meet higher industrial efficiency. This paper reviews the main factors influencing the thermal insulation performance of TBCs, such as material, coating thickness, and structure. The heat transfer mechanism of the coating is summarized, and the degradation mechanism of the thermal insulation is analyzed from the perspective of the coating structure. Finally, the recent advances in improving the thermal insulation and lifetime of coatings are reviewed in terms of advanced materials and structural design, which will benefit advanced TBCs in future engineering applications and provide guidance for the next generation of high thermal insulating TBCs