Performance Degradation Prediction of Proton Exchange Membrane Fuel Cell Based on CEEMDAN-KPCA and DA-GRU Networks

In order to improve the performance degradation prediction accuracy of proton exchange membrane fuel cell(PEMFC),a fusion prediction method(CKDG)based on adaptive noise complete ensemble empirical mode decomposition(CEEMDAN),kernel principal component analysis(KPCA)and dual attention mechanism gated recurrent unit neural network(DA-GRU)was proposed.CEEMDAN and KPCA were used to extract the input feature data sequence,reduce the influence of random factors,and capture essential feature components to reduce the model complexity.The DA-GRU network helps to learn the feature mapping relationship of data in long time series and predict the changing trend of performance degradation data more accurately.The actual aging experimental data verify the performance of the CKDG method.The results show that under the steady-state condition of 20%training data prediction,the CKDA method can reduce the root mean square error(RMSE)by 52.7%and 34.6%,respectively,compared with the traditional LSTM and GRU neural networks.Compared with the simple DA-GRU network,RMSE is reduced by 15%,and the degree of over-fitting is reduced,which has higher accuracy.It also shows excellent prediction performance under the dynamic condition data set and has good universality.

负载二硫化钼纳米片光敏剂的聚氨酯脲水凝胶的制备与性能

采用聚乙二醇和异佛尔酮二异氰酸酯为主要原料合成预聚体,A-95改性的MoS2纳米片(N-MoS2)作为封端剂,加入白及多糖(BSP)水溶液作为扩链剂,制备了双重交联的聚氨酯脲水凝胶。采用红外光谱、透射电镜、扫描电镜和X射线衍射对N-MoS2纳米片和凝胶的结构和形貌进行了表征,采用拉伸强度-应变测试和抗菌实验对其力学性能和抗菌性能进行了测试。结果表明,改性的N-MoS2纳米片具有单层或少层结构,在可见光照下对大肠杆菌和金黄色葡萄球菌的抑菌效果明显。水凝胶样品MPUBs的拉伸强度随N-MoS2含量的增加先增大后减小,溶胀率先减小后增大;当N-MoS2纳米片的添加量为2%时,得到的MPUB5凝胶样品的综合性能最佳,溶胀率为177.8%、溶胀拉伸强度达1.28 MPa,并且在2种细菌的培养基中均能观察到明显抑菌圈,显示出良好的抗菌性能。

The age at first consumption of forage in calves and its effect on growth and rumination in the short‑and long‑term

Background Previous investigations into the effect of dietary forage on calf performance have been inconsistent,and there is a paucity of information exploring the effect of age on the growth performance and rumination of calves.Eighty-four female Holstein calves(41.5±4.2 kg)were enrolled at birth,a subset of the calves were fed calf starter only(CON,n=21)while the rest(n=63)were classified into three treatment groups:the early(EHAY,n=26,5.1±0.8 d),the middle(MHAY,n=21,7.9±0.8 d)and the late(LHAY,n=16,12.1±1.4 d)hay consumers.The short-term effect of the age at first forage consump-tion(AFF)on calves’feed intake was monitored until d 84.In addition,the long-term effects of AFF on body weight,structural growth and rumination behavior were recorded until d 196.Rumen samples were collected on d 1,7,35,84 and 196 to ana-lyze the rumen fermentation,while fecal samples were collected from d 78 to 84 to estimate digestibility parameters.Results Treatment had no effect on feed intake.While,the EHAY calves tended to have lower BW and ADG compared to LHAY and CON calves.Several total-tract apparent digestibility parameters and digestible nutrients intake were significantly lower in EHAY calves compared with CON and LHAY calves.Calves in the EHAY group tended to begin ruminating ealier,while CON calves were the latest(12.3 vs.15.5 days of age).A treatment and time interaction was present for rumination time due to greater rumination in calves consuming hay compared to CON calves in week 10 to 12,the differences in rumination disappeared afterwards,no long-lasting significant differences in the rumina-tion and rumen fermentation parameters were found between treatments.Conclusions In conclusion,this study showed that hay consumption earlier in life(in the first week,around 5 days of life)could negatively affect the growth of the calf in the short and long term.Compared to consuming hay from the second week(around 12 days of life)or feeding concentrate only without hay,starting to consume hay from the first week could compromise nutrient digestibility and digestible nutrient intake independent of developing rumination behaviour and rumen fermentation.

Coupling between the Cenozoic west Pacific subduction initiation and decreases of atmospheric carbon dioxides

At the beginning of the Cenozoic,the atmospheric CO_(2)concentration increased rapidly from~2000 ppmv at 60 Ma to~4600 ppmv at 51 Ma,which is 5–10 times higher than the present value,and then continuous declined from~51 to 34 Ma.The cause of this phenomenon is still not well understood.In this study,we demonstrate that the initiation of Cenozoic west Pacific plate subduction,triggered by the hard collision in the Tibetan Plateau,occurred at approximately 51 Ma,coinciding with the tipping point.The water depths of the Pacific subduction zones are mostly below the carbonate compensation depths,while those of the Neo-Tethys were much shallower before the collision and caused far more carbonate subducting.Additionally,more volcanic ashes erupted from the west Pacific subduction zones,which consume CO_(2).The average annual west Pacific volvano eruption is 1.11 km~3,which is higher than previous estimations.The amount of annual CO_(2)absorbed by chemical weathering of additional west Pacific volcanic ashes could be comparable to the silicate weathering by the global river.We propose that the initiation of the western Pacific subduction controlled the long-term reduction of atmospheric CO_(2)concentration.

CO_2 emission and organic carbon burial in the Xinanjiang Reservoir

In order to understand the effect of river impoundment on carbon dynamics, a large reservoir in a subtropical area, the Xinanjiang Reservoir, was investigated in detail. CO_2 emissions from the water–air interface was studied, as was organic carbon burial in sediment. The results show a significant seasonal difference in CO_2 emissions. River impoundment led to the enhancement of aquatic photosynthesis, generating large amounts of authigenic organic carbon that was then buried in sediment.

Design of an augmented reality display based on polarization grating

A new optical system for an augmented reality(AR) display is proposed in this paper.The optical system mainly includes a ray deflector, coupling input grating, optical waveguide, and coupling output grating.Both the ray deflector and the coupling input grating are designed based on the diffraction characteristics of the polarization grating, and the coupling output grating is the Bragg reflection grating.Compared with other AR schemes, this AR optical system not only reduces the number of projections from two to one, but also improves the efficiency of light coupling into the optical waveguides.The energy loss is reduced by utilizing the single-order diffraction characteristics of the polarization grating in its coupling input structure.The light deflector uses the polarization selectivity of the polarization grating and the characteristics of the rotating light of the twisted nematic liquid crystal layer to realize beam deflection.The working principle of the optical system is experimentally and theoretically demonstrated.

Deep-sea coral evidence for dissolved mercury evolution in the deep North Pacifi c Ocean over the last 700 years

The ocean is an important inventory of anthropogenic mercury(Hg),yet the history of anthropogenic Hg accumulation in the ocean remains largely unexplored.Deep-sea corals are an emerging archive of past ocean chemistry,which take in sinking or suspended particulate organic matter as their food sources.Such organic matter would exchange Hg with the local seawater before being consumed by the deepsea corals.As such,the organics preserved in the coral skeleton may record the Hg evolution of the ambient seawater during the time of coral growth.Here,we report the first data on Hg concentrations variability of a deep-sea proteinaceous coral in the oligotrophic North Pacific at the water depth of 1249 m,in attempt to understand the transfer of anthropogenic Hg into the deep Pacific ocean over the last seven centuries.We find that the Hg concentrations of different coral growth layers have remained relatively constant albeit with considerable short-term variability through time.The overall stable Hg concentration of the last seven centuries recorded in our sample suggests that anthropogenic pollution is not yet a clearly resolvable component in the deep oligotrophic North Pacific waters,in agreement with rece nt estimation from modelling works and observational studies of modern seawater profiles.As there is hardly an unambiguous way to separate anthropogenic Hg from the natural background based on recent seawater profiles,our historical data provide valuable information helping to understand the oceanic cycle of Hg through time.

Potassium isotopic signatures of modern offshore detrital sediments from different climatic regimes and the implications

Potassium isotopes are a novel tracer for continental weathering.Previous K isotope studies on chemical weathering generally targeted weathering profiles under a particular climate region,yet the effects of chemical weathering on K isotopes under different climatic backgrounds remain unclear.Moreover,little is known about the K isotope signatures of modern unconsolidated detrital sediments.Here,we report K isotopic data of surficial seafloor sediments from continental shelves along the east coast of China(ECC),as well as those around the tropical Hainan island in the northern South China Sea.The ECC sediments have a relatively narrow distribution ofδ^(41)K(with reference to NIST3141a)values,which range from(-0.40±0.01)‰to(-0.57±0.04)‰,with an average of(-0.51±0.09)‰.By contrast,δ^(41)K values of Hainan offshore sediments display a larger variation,ranging from(-0.28±0.07)‰to(-0.67±0.02)‰.Theδ^(41)K values of Hainan offshore sediments exhibit negative correlations with the chemical index of alteration(CIA),Al/K,Ti/K,and total iron(FeT),which underlines the control of chemical weathering on K isotopic signatures of detritus inputs into oceans.We also measured Mg isotope compositions for the same samples;interestingly,the variability inδ^(26)Mg of the samples is small(~0.24‰)for all ECC and Hainan offshore sediments,andδ^(26)Mg values do not show clear correlations with indexes of chemical weathering.Our study demonstrates the link between K isotopic variability of detrital sediments and climatic conditions including rainfall intensity,which indicates that K isotopes of the detrital component of marine sediments could be applied to study Earth’s climate in deep time.Theδ^(41)K values of the offshore detrital sediments are significantly less variable than those of pelagic marine sediments,highlighting the importance of distinguishing the effects of diagenesis and neoformation of clay minerals from continental weathering in attempts to study deep-time climate-weathering link by K isotopes in detrital sedimentary records.

Transdermal treatment for malignant melanoma by aptamer-modified tetrahedral framework nucleic acid delivery of vemurafenib

Melanoma is one of the most malignant skin tumors, whose high invasion is generally associated with BRAF gene mutation. Although new chemotherapeutic drugs, such as vemurafenib, have been developed to inhibit the growth of melanoma, these drugs are usually administered intravenously or orally, resulting in toxic side effects on major tissues and organs. Tetrahedral framework nucleic acids(tFNAs) are a novel type of DNA nanostructures with excellent biocompatibility and versatility which have been proven to penetrate through skin barrier with ease. In this study, we prepared t FNAs with vemurafenib and connected DNA aptamer AS1411 at the apex of t FNAs(AS1411-tFNAs/vemurafenib). On one hand, AS1411-tFNAs/vemurafenib could kill melanoma cells by blocking the mutated BRAF gene in vitro. Compared with free vemurafenib, AS1411-tFNAs/vemurafenib had no obvious toxicity to normal cells. On the other hand,AS1411-tFNAs could transfer vemurafenib to cross through the skin barrier and permeate into tumor tissues. In vivo, transdermal delivery of AS1411-t FNAs/vemurafenib could inhibit the growth of human A375melanoma, whose inhibiting effect was stronger than intravenous administration of vemurafenib. These results demonstrated the application prospects of tFNAs combined with chemotherapeutic drugs in skin tumors.

Microstructural evolution and energetic characteristics of TiZrHfTa_(0.7)W_(0.3)high-entropy alloy under high strain rates and its application in high-velocity penetration

Energetic structural materials(ESMs)integrated a high energy density and rapid energy release with the ability to serve as structural materials.Here,a novel triple-phase TiZrHfTa_(0.7)W_(0.3)high-entropy alloy(HEA)was fabricated and investigated as a potential ESM.A hierarchical microstructure was obtained with a main metastable body-centered-cubic(BCC)matrix with distributed Ta-W-rich BCC precipitates of various sizes and interwoven hexagonal close-packed(HCP)lamellar nano-plates.The compressive me-chanical properties were tested across a range of strain rates and demonstrated a brittle-to-ductile tran-sition as the strain rate increased while maintaining a high ultimate strength of approximately 2.5 GPa.This was due to the phase transformation from metastable matrix BCC to HCP structures.In addition,during the dynamic deformation,metal combustion originating from the failure surface was observed.Furthermore,the composition of the fragments was studied,and the results indicated that the addition of tungsten promoted combustion.Finally,the potential application of this HEA was evaluated by high-velocity penetration tests,and the results were compared to other typical structural materials for pene-trators and bullets.A comparison was conducted by assessing the geometries of the penetration channel employing two dimensionless parameters normalized by the projectile size,representing longitudinal and lateral damage,respectively.The normalized depth of the TiZrHfTa_(0.7)W_(0.3)HEA projectile was comparable to those of the other investigated materials,but the normalized diameter was the largest,showing an excellent ability to deliver lateral damage.

无过渡金属参与杂环甲基化合物与醇的选择性有氧碳-烷基化反应

研究发现,使用适当的碱并将反应在空气下进行,不使用任何外加催化剂即可高效实现杂环甲基化合物与各种醇的选择性脱水碳-烷基化反应.控制实验说明该反应的确不需要过渡金属催化剂,机理研究也显示了碱和空气在反应中的关键作用:该反应实际上通过碱促进下空气将醇氧化为羰基化合物的方式启动,生成的羰基化合物中间体进而催化烷基化反应的顺利进行、从而选择性地得到烷基化产物,羰基化合物可在反应中再生、回收、完成催化循环.该方法具有底物适用范围广、无需过渡金属催化剂及配体、无需惰性气体保护、操作简单、成本较低、产物无过渡金属残留等优点,因此是一种较为实用的杂环化合物的官能团化方法.

A humidity resistant and high performance triboelectric nanogenerator enabled by vortex-induced vibration for scavenging wind energy

Wind energy is a promising renewable energy source for a low-carbon society.This study is to develop a fully packaged vortexinduced vibration triboelectric nanogenerator(VIV-TENG)for scavenging wind energy.The VIV-TENG consists of a wind vane,internal power generation unit,an external frame,four springs,a square cylinder and a circular turntable.The internal power generation unit consists of polytetrafluoroethylene(PTFE)balls,a honeycomb frame and two copper electrodes.Different from most of the previous wind energy harvesting TENGs,the bouncing PTFE balls are fully packaged in the square cylinder.The distinct design separates the process of contact electrification from the external environment,and at the same time avoids the frictional wear of the ordinary wind energy harvesting TENGs.The corresponding VIV parameters are investigated to evaluate their influence on the vibration behaviors and the energy output.Resonant state of the VIV-TENG corresponds to the high output performance from the VIV-TENG.The distinct,robust structure ensures the full-packaged VIV-TENG can harvest wind energy from arbitrary directions and even in undesirable weather conditions.The study proposes a novel TENG configuration for harvesting wind energy and the VIV-TENG proves promising powering micro-electro-mechanical appliances.

Limited Contribution of Preferential Dissolution to Radiogenic Uranium Isotope Disequilibrium Observed in Weathered Moraines

Radiogenic uranium isotope disequilibrium(^(234)U/^(238)U) has been used to trace a variety of Earth surface processes,and is usually attributed to direct recoil of ^(234)Th and preferential dissolution of radioactively damaged lattices at the mineral surface.However,the relative contribution of these two mechanisms in the natural environment remains unresolved,making it hard to use the extent of disequilibrium to quantify processes such as weathering.This study tests the contribution of preferential dissolution using well-characterized weathered moraines and river sediments from the southeastern Tibetan Plateau.The observations show that weathering of recent moraines where the contribution from direct recoil is negligible and is not associated with depletion of ^(234)U at the mineral surface.It suggests a limited role for preferential dissolution in this setting.We attribute this lack of preferential dissolution to a near-to-equilibrium dissolution at the weathering interfaces,with little development of etch pits associated with radioactively damaged energetic sites.

Blinking CsPbBr_(3) perovskite nanocrystals for the nanoscopic imaging of electrospun nanofibers

Blinking fluorophore perovskite nanocrystals (NCs) were employed to image the fine structure of the polystyrene (PS) electrospun fibers. The conditions of CsPbBr3 NCs embedded and dispersed into PS were investigated and optimized. The stochastic optical reconstruction microscopy is employed to visualize the fine structure of the resulted CsPbBr3@PS electrospun fibers at sub-diffraction limit. The determined resolution in the reconstructed nanoscopic image is around 25.5 nm, which is much narrower than that of conventional fluorescence image. The complex reticulation and multicompartment in bead sub-diffraction-limited structures of CsPbBr3@PS electrospun fibers were successfully mapped with the help of the stochastic blinking properties of CsPbBr3 NCs. This work demonstrated the potential applications of CsPbBr3 perovskite NCs in super-resolution fluorescence imaging to reconstruct the sub-diffraction-limited features of polymeric material.

Prediction and controlling for welding deformation of propeller base structure

Welding deformation often brings about manufacturing problems such as dimensional inaccuracies during assembly and reduces fabrication efficiency.Prediction and controlling welding deformation can help to improve the quality of welded structures.In this paper,the welding deformation of propeller base struc-tures is predicted by means of numerical approaches and mechanical constraints are proposed to control deformations in welding process.Thermal elasto-plastic finite element method(TEP FEM)is employed to simulate welding process of the base structure.Computed accuracy of welding deformation by TEP FEM analysis is verified by comparing with experimental data of tee joint welding.Results show that welding deformations of the base mainly comprise out-of-plane distortion of ring fringe and radial distortion of cylindrical plate.Exerting mechanical constraints of fixed points at fringe and rigid supports inside cylin-der can decrease out-of-plane and radial distortions effectively.The numerical approach adopted in this article can serve as an effective tool to optimize welding process planning in integrated design method.

A bio-inspired and self-powered triboelectric tactile sensor for underwater vehicle perception

Marine mammals relying on tactile perception for hunting are able to achieve a remarkably high prey capture rate without visual or acoustic perception.Here,a self-powered triboelectric palm-like tactile sensor(TPTS)is designed to build a tactile perceptual system for underwater vehicles.It is enabled by a three-dimensional structure that mimics the leathery,granular texture in the palms of sea otters,whose inner neural architecture provides additional clues indicating the importance of tactile information.With the assistance of palm structure and triboelectric nanogenerator technology,the proposed TPTS has the ability to detect and distinguish normal and shear external load in real-time and approximate the external stimulation area,especially not affected by the touch frequency,that is,it can maintain stable performance under high-frequency contact.The results show that the TPTS is a promising tool for integration into grippers mounted on underwater vehicles to complete numerous underwater tasks.

Isotopic fingerprinting of dissolved iron sources in the deep western Pacific since the late Miocene

Iron(Fe)is a productivity-limiting nutrient in the ocean.However,the sources of dissolved Fe(dFe)in the deep ocean and how they respond to tectonic and climate changes are still poorly understood.In the northern hemisphere,dust flux to the low-latitude western Pacific has increased dramatically since the late Miocene associated with intense aridification of the Asian inland.Meanwhile,the terrigenous material supply to the open ocean might have also changed as a result of the reorganization of the Pacific circulation due to the gradual closure of seaways in the low latitudes.Therefore,the western Pacific is a characteristic region for understanding the sources of dFe in the deep ocean and their responses to long term climate changes.Here,we present data on isotopic evolution of dFe and dissolved Pb since^8 Ma based on ferromanganese crust METG-03(16.0°N,152.0°E,3850 m water depth)in the western Pacific deep water.Our results show thatδ56Fe of the crust remains fairly stable since the late Miocene,i.e.,about-0.32±0.08‰(2SD).We infer thatδ56Fe of dFe in the deep western Pacific is relatively invariant at^0.45±0.1‰based on the Fe isotopic fractionation between hydrogenetic crust and the seawater dissolved component.The reconstructed isotope signature is similar to the measuredδ56Fe value(0.37±0.15‰)of the intermediate to deep waters in the modern low-latitude western Pacific region close to the island arcs,but is significantly higher than that of the eastern Pacific deep waters near South America which is controlled by the reductive dissolution of continental shelf sediments and the hydrothermal inputs(δ56Fe<-0.1‰).The deep-water 206Pb/204Pb ratio recorded by METG-03 displays systematic increase at about 8–4 Ma,reflecting increased input from sediment dissolution of low-latitude island arcs associated with reorganization of the western Pacific deep circulation.Notably,Fe isotopes of terrigenous materials from different sources are similar,while their dissolved Fe isotopic signatures released to the ocean are mainly controlled by the mechanism of particle dissolution.The stability ofδ56Fe and systematic changes in Pb isotopes over the last^8 Ma thus suggest that Asian dust dissolution and hydrothermal inputs are likely only minor sources of dFe in the low-latitude deep western Pacific,while the acquisition and transport of dFe from shelf sediments by organic ligand binding in the oxic environment is the major dFe source which keeps stable on tectonic time scales since the late Miocene.

Tetrahedral framework nucleic acids regulate osteogenic differentiation potential of osteoporotic adipose-derived stem cells

Osteoporosis(OP)is a noncommunicable bone disease caused by a shift in the balance between os-teoblasts and osteoclasts,and can severely affect the health of elderly persons.Autologous stem-cell transplantation can improve reduced bone density and weakened fracture healing abilities in patients with OP.However,OP can adversely affect the osteogenesis and proliferation abilities of autologous adipose-derived stem cells(ASCs).Therefore,an effective drug is required to facilitate autologous ASCs to recover their osteogenic and proliferative potential.Tetrahedral framework nucleic acid(tFNA)is a new type of nanomaterial that has ability to regulate the biological behavior of cells effectively and en-hance the bioactivity of stem cells.In this study,we examine the effects of tFNAs on the osteogenic differentiation and proliferation abilities of ASCs in rats with OP.The results indicate that the 250 nmol/L tFNAs can considerably increase the expression of osteogenesis-related markers,effectively promote the proliferation and osteogenic differentiation of osteoporotic ASCs(OP-ASCs),and help them to regain their osteogenic and proliferative potential.In short,tFNAs can enable OP-ACSs to recover their osteogenic po-tential and promote their proliferation and,therefore,can play a key regulatory role in autologous ASC transplantation.

Design of an all-optical logic sequence generator based on polarization holographic gratings

In this Letter, an all-optical logic sequence generator based on two different polarization holographic gratings has been proposed and demonstrated, which has one input port and four output ports. The polarization state of input light signal determines logic output signals. It can produce four kinds of logic sequence output signals:1000, 0100, 0010, and 0001, corresponding to the input light signal of four different polarization states: the p-linear, s-linear, left-handed circular, and right-handed circular. The two polarization gratings have been fabricated, and the working principle of the logic sequence generator has been proved by diffraction pattern analysis of polarization gratings.

A Triboelectric-Based Artificial Whisker for Reactive Obstacle Avoidance and Local Mapping

Since designing efficient tactile sensors for autonomous robots is still a challenge,this paper proposes a perceptual system based on a bioinspired triboelectric whisker sensor(TWS)that is aimed at reactive obstacle avoidance and local mapping in unknown environments.The proposed TWS is based on a triboelectric nanogenerator(TENG)and mimics the structure of rat whisker follicles.It operates to generate an output voltage via triboelectrification and electrostatic induction between the PTFE pellet and copper films(0.3 mm thickness),where a forced whisker shaft displaces a PTFE pellet(10 mm diameter).With the help of a biologically inspired structural design,the artificial whisker sensor can sense the contact position and approximate the external stimulation area,particularly in a dark environment.To highlight this sensor’s applicability and scalability,we demonstrate different functions,such as controlling LED lights,reactive obstacle avoidance,and local mapping of autonomous surface vehicles.The results show that the proposed TWS can be used as a tactile sensor for reactive obstacle avoidance and local mapping in robotics.