Vinylene-linked two-dimensional covalent organic frameworks (V-2D-COFs) have shown great promise in electronics and optoelectronics. However, only a few reactions for V-2D-COFs have been developed ...hitherto. Besides the kinetically low reversibility of C=C bond formation, another underlying issue facing the synthesis of V-2D-COFs is the attainment of high (E)-alkene selectivity to ensure the appropriate symmetry of 2D frameworks. Here, we tailor the E/Z selectivity of the Wittig reaction by employing a proper catalyst (i.e., Cs2CO3) to obtain more stable intermediates and elevating the temperature across the reaction barrier. Subsequently, the Wittig reaction is innovatively utilized for the synthesis of four crystalline V-2D-COFs by combining aldehydes and ylides. Importantly, the efficient conjugation and decent crystallinity of the resultant V-2D-COFs are demonstrated by their high charge carrier mobilities over 10 cm2 V−1 s−1, as revealed by non-contact terahertz (THz) spectroscopy.
Flexible conductive films are a key component of strain sensors, and their performance directly affects the overall quality of the sensor. However, existing flexible conductive films struggle to ...maintain high conductivity while simultaneously ensuring excellent flexibility, hydrophobicity, and corrosion resistance, thereby limiting their use in harsh environments. In this paper, a novel method is proposed to fabricate flexible conductive films via centrifugal spinning to generate thermoplastic polyurethane (TPU) nanofiber substrates by employing carbon nanotubes (CNTs) and carbon nanofibers (CNFs) as conductive fillers. These fillers are anchored to the nanofibers through ultrasonic dispersion and impregnation techniques and subsequently modified with polydimethylsiloxane (PDMS). This study focuses on the effect of different ratios of CNTs to CNFs on the film properties. Research demonstrated that at a 1:1 ratio of CNTs to CNFs, with TPU at a 20% concentration and PDMS solution at 2 wt%, the conductive films crafted from these blended fillers exhibited outstanding performance, characterized by electrical conductivity (31.4 S/m), elongation at break (217.5%), and tensile cycling stability (800 cycles at 20% strain). Furthermore, the nanofiber-based conductive films were tested by attaching them to various human body parts. The tests demonstrated that these films effectively respond to motion changes at the wrist, elbow joints, and chest cavity, underscoring their potential as core components in strain sensors.
Marine renewable energy resources are important for clean energy development. Research on the combined assessment of wind and wave resources, especially in tropical cyclone (TC) affected area is ...still rare. This study is to assess the potential combined wind and wave energy in the coastal waters of China, where TCs frequently occurred. The study utilizes the blended wind field with a parametric TC model based on the ECMWF reanalysis wind data from 1979 to 2013 for assessing potential wind energy, and the waves generated by the same wind data using the FVCOM-SWAVE model for assessing wave energy. The combined wind and wave energy density and annual power generation are analyzed. The potential energy from wind and waves at 15 nearshore locations along China east coasts are estimated. The results show that the frequency and intensity of TCs have a considerable impact on the distribution of density and stability of wind and wave energy, especially in the southeastern coastal areas of China. Suggestions of site selection of co-located wind and wave farm in the coastal waters of China are given. The research outcome provides a useful guidance for the selection of potential sites and design of wind and wave energy converters along the China coasts.
•Combined wind and wave resources in China seas are fully assessed.•The impacts of tropical cyclones on wind and wave energy in the study area are investigated.•Site selection of the co-located wind and wave farm in China seas are recommended.
Key Generation for Internet of Things Xu, Weitao; Zhang, Junqing; Huang, Shunqi ...
ACM computing surveys,
01/2022, Letnik:
54, Številka:
1
Journal Article
Recenzirano
Key generation is a promising technique to bootstrap secure communications for the Internet of Things devices that have no prior knowledge between each other. In the past few years, a variety of key ...generation protocols and systems have been proposed. In this survey, we review and categorise recent key generation systems based on a novel taxonomy. Then, we provide both quantitative and qualitative comparisons of existing approaches. We also discuss the security vulnerabilities of key generation schemes and possible countermeasures. Finally, we discuss the current challenges and point out several potential research directions.
•Geomorphic evolution of the deltaic channel and active river mouth is evaluated.•Morphologic variability of the active delta has a distinct spatial variance.•Offshore fine sediment dispersal ...processes are simulated and quantified.•The new river regime can improve channel stability and intensify deltaic recession.
Intensified human interventions in river basins and deltas lead to more complexities of environmental changes during the Anthropocene. Changes in river regime especially a dramatic reduction in sediment delivery increase challenges of the morphological and ecological sustainability of river deltas. In evaluating deltaic risks and sustainable solutions, researches are often limited to single geomorphic units of the deltaic system, and investigations of sediment source to sink transfer at river deltas under recent river regimes are often missing. The Yellow River Delta (YRD) presents as a typical megadelta under stressors induced by changing environments. This study utilizes a period of 20-yr high-resolution topography data of the deltaic channel and its subaqueous delta to investigate sediment transport and source to sink process by integrated methods of field measurements and numerical simulations. The results indicate that the deltaic channel has transitioned from net accretion to erosion after the implementation of the Water-Sediment Regulation Scheme (WSRS) in 2002. The active river mouth experienced a slow accretion phase since the river channel diverted to Qing 8 channel, with a reduced vertical deposition rate of 0.15 m/yr, whilst its adjacent Gudong littoral zone had a −0.11 m/yr erosion rate. Under the new fluvial regime, the river-borne suspended sediment tends to transport southwards to the Laizhou Bay, followed by the river-derived sediment transport eastward and northward to the offshore delta. It is clear that with the continued human activities in the region, the YRD is at the potential state of deltaic transition both in the deltaic channel and its subaqueous delta. This transition is believed to be beneficial to the deltaic channel stability, but it could significantly impact on the geomorphic and ecologic sustainability of the entire deltaic system.
Weft insertion based on electromagnetic launch technology is a novel and very promising approach for super broad-width (6–12 m) (SBW) looms. There are considerable challenges involved in designing ...such a system, including analyzing the electromagnetic field while incorporating the effect of a clip weft device, and accurately calculating the electromagnetic and motion parameters of the weft insertion mechanism. In this study, an electromagnetic launch, non-striking weft insertion method for an SBW loom is proposed. The electromagnetic field is analyzed with the finite element method and includes the effect of a clip weft device. Simulation of the motion, analysis of the maximum flight speed of the clip weft device and the work done by electromagnetic force are presented. We also describe an experimental model for electromagnetic launch weft insertion and calculate the electromagnetic force required for weft insertion, using analytical methods and numerical finite element methods. Comparison of the results with measured values shows that this electromagnetic launch weft insertion system has good flexibility. In addition, the weft insertion speed required for different width looms can be obtained by changing the current of the coil or the coil stage number of the launching system.
Coastal flooding due to sea level rise significantly affects socioeconomic development. The dynamic nature of coastal flood risk (CFR) and socioeconomic development level (SDL) leads to uncertainties ...in understanding their future interplay. This ambiguity challenges coastal nations in devising effective flood adaptation and coastal management strategies. This study quantitatively examines the expected GDP affected (EGA) and population affected (EPA) by coastal flooding in China's coastal zone (CCZ) from 2030 to 2100 under various climate scenarios (RCP2.6-SSP1, RCP4.5-SSP2, and RCP8.5-SSP5). The future SDL in CCZ is assessed using a method combining the analytic hierarchy process with entropy weight. The future CFR-SDL dynamic relationship is analyzed using the coupling coordination degree (CCD) model. The results reveal that in CCZ under the RCP2.6-SSP1, RCP4.5-SSP2, and RCP8.5-SSP5 scenarios: by 2100, the EGA and EPA will reach $814.90 billion & 6.17 million people, $828.16 billion & 7.63 million people, and $1568.83 billion & 8.05 million people, respectively, where the coastal cities in Jiangsu and Guangdong provinces will face more obvious risks of socioeconomic losses; The total area in the CCZ at “Very high” and “High” level of socioeconomic development by 2100 is projected to reach 11.33 × 103 km2, 12.86 × 103 km2, and 15.82 × 103 km2, respectively, with the Pearl River Delta, Yangtze River Delta, and Tianjin-Hebei remaining pivotal for CCZ's socioeconomic growth. Cities such as Lianyungang, Jiaxing, Shenzhen, Dongguan, and Foshan show notable CCD characteristics, and addressing the trade-off between SDL and CFR is crucial in achieving sustainable development. This study highlights the potential socioeconomic impacts of coastal flooding and emphasizes the importance of considering the interrelationship between CFR and SDL when developing coastal flood adaptation policies.
Display omitted
•Comprehensive analysis of socioeconomic impacts of coastal flooding in the 21st century China’s coastal zone (CCZ).•Utilized an innovative combined method to project the future socioeconomic pattern of CCZ.•Explored the interplay between escalating coastal flood risks and socioeconomic development in the CCZ.•Provided insights for policymakers on harmonizing coastal flood risk management with socioeconomic development in the CCZ.
•Yellow River sediment delivery has decreased over 99% under the human interference.•Significant reduction of Yellow River sediment input occurred in 1985.•The new regime of riverine delivery shapes ...deltaic morphology at multiple timescales.•Approximately 68% of sediment input deposited near the active Yellow River mouth.•Active Yellow River mouth is transforming from the accretion to erosion state.
The Yellow River subaqueous delta (YRSD), once the most rapid depo-center among river deltas worldwide, has been under the risks of subsidence and degradation due to the new regime of riverine delivery affected by human interventions. Utilizing hydrologic and bathymetric surveying datasets, we examined the latest regime of river input from the perspective of water-sediment relationship, and the responding morphological evolutionary processes of active YRSD over a period of 20 years between 1996 and 2016. Results show that the new discharge regime is strongly interfered by the Water-Sediment Regulation Scheme (WSRS), characterized by a more drastic decline of sediment load than that of water discharge; more harmonious relationship between water and sediment discharges in the lower reach of the river to the sea; coarser sediment delivery and low suspended sediment concentration (SSC). We identified inverse erosion-accretion trends in the subaqueous region: net accretion of 0.15 m/yr in the active Yellow River mouth (AYRM) and severe erosion of −0.1 m/yr in the Gudong littoral zone (GDLZ). As the primary sink for sediment delivery, AYRM received approximately 68% of sediment delivery during the study period and sedimentation was mainly occurred in the shallower area where water depth was less than 10 m. In addition, recent morphological evolution of AYRM is found to have undergone through four stages, namely: moderate accretion (1996–2002), rapid accretion (2002–2007), reduced accretion (2007–2015) and rapid erosion (2015–2016). The new regime of riverine delivery presents multiple spatiotemporal scales in shaping deltaic morphology. Compared with the previous research, we present the morphological evolution of deltaic system over decadal timescale is strongly influenced by reduction of sediment supply derived from basin-scale human impacts, and the variability of subaqueous portion during the study period is closely related to inter-annual variability of river input. Besides, the building of AYRM is shaped by event-scale WSRS induced-floodwater, and decade-scale change of sediment pathway governed by frequent mouth channel migration. The results show, for the first time, that AYRM has experienced a significant erosion since the implementation of WSRS, with a decline of 99% sediment delivery in 2016 compared to the natural mode during 1950s. The results also indicate that to maintain the erosion-accretion balance of AYRM, an estimation of 41.4–62.3 Mt/yr sediment delivery should be kept. Due to the fluvial regime change from the natural to the highly human-regulated modes, the AYRM, as well as the whole YRSD, is expected to be transforming from the accretion to erosion states.
The upgrading of traditional chiller plants to the high-efficiency refrigerator room is conducive to effective utilization and conservation of energy. An energy-saving method of chiller plants group ...control based on Kernel Ridge Regression and Genetic Algorithm are presented. Combined with machine learning and the classic model of the chiller plants, the multiple nonlinear problems between the system parameters of the chiller plants are solved. A more detailed group control model of chiller plants is established, which is suitable for multiple chillers, variable-speed pumps, and variable-frequency fans. Incorporate the startup time of the chiller, the difference between the actual cooling capacity and the target cooling capacity into the penalty function, and use the Genetic Algorithm for multi-dimensional optimization to find the best efficiency point of the entire refrigeration room and achieve the goal of energy saving. A comparative analysis of the actual operation of the cold room system of a large electronics factory in Guangdong for three months is carried out. Compared with the traditional PID algorithm, the three-month power saving rate of this group control energy saving method is: 31.34%, 14.33%, 19.22%.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The H4 subtype of avian influenza viruses has been widely distributed among wild birds. During the surveillance of the avian influenza virus in Shanghai from 2019 to 2021, a total of 4,451 samples ...were collected from wild birds, among which 46 H4 subtypes of avian influenza viruses were identified, accounting for 7.40% of the total positive samples. The H4 subtype viruses have a wide range of hosts, including the spot-billed duck, common teal, and other wild birds in Anseriformes. Among all H4 subtypes, the most abundant are the H4N2 viruses. To clarify the genetic characteristics of H4N2 viruses, the whole genome sequences of 20 H4N2 viruses were analyzed. Phylogenetical analysis showed that all 8 genes of these viruses belonged to the Eurasian lineage and closely clustered with low pathogenic avian influenza viruses from countries along the East Asia-Australia migratory route. However, the PB1 gene of 1 H4N2 virus (NH21920) might provide its internal gene for highly pathogenic avian influenza H5N8 viruses in Korea and Japan. At least 10 genotypes were identified in these viruses, indicating that they underwent multiple complex recombination events. Our study has provided a better epidemiological understanding of the H4N2 viruses in wild birds. Considering the mutational potential, comprehensive surveillance of the H4N2 virus in both poultry and wild birds is imperative.
