阻燃剂对微孔聚氨酯弹性体性能的影响

以可膨胀石墨(EG)、可膨胀石墨/三聚氰胺聚磷酸盐(EG/MPP)和可膨胀石墨/三聚氰胺聚磷酸盐/甲基膦酸二甲酯(EG/MPP/DMMP)为阻燃剂制备了具有阻燃功能的微孔聚氨酯弹性体(MPUE),通过热重分析、极限氧指数(LOI)测定仪及水平垂直燃烧测试,研究了阻燃剂对微孔聚氨酯弹性体热降解行为和阻燃性能的影响,重点分析了阻燃剂对力学性能、动态减振、耐蠕变性能的影响。结果表明,单独添加EG,在质量分数20%以上才对MPUE具有较明显的阻燃效果,但随着EG含量增加,MPUE的动态减振效果和耐蠕变性能变差。EG与MPP复配,对MPUE的阻燃性能有显著改善,但MPUE的动态减振和耐蠕变性能等指标仍偏高。EG/MPP/DMMP复配,阻燃性能进一步提升,并且改善了动态减振性能和耐蠕变性能,质量分数为11%,m(EG)/m(MPP)/m(DMMP)=1:2:1时,MPUE的LOI仍有27.8%,动静刚度比降到了1.35以内。

New insights into the pre-lithiation kinetics of single-crystalline Ni-rich cathodes for long-life Li-ion batteries

Developing single-crystalline Ni-rich cathodes is an effective strategy to improve the safety and cycle life of Li-ion batteries(LIBs).However,the easy-to-loss of Li and O in high-temperature lithiation results in unsatisfactory ordered layered structure and stoichiometry.Herein,we demonstrate the synthesis of highly-ordered and fully-stoichiometric single-crystalline LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2)(SC-NCM83)cathodes by the regulation of pre-lithiation kinetics.The well-balanced pre-lithiation kinetics have been proved to greatly improve the proportion of layered phase in the intermediate by inhibiting the formation of metastable spinel phase,which promoted the rapid transformation of the intermediate into highly-ordered layered SC-NCM83 in the subsequent lithiation process.After coating a layer of Li_(2)O–B_(2)O_(3),the resultant cathodes deliver superior cycling stability with 90.9%capacity retention at 1C after 300 cycles in pouch-type full batteries.The enhancement mechanism has also been clarified.These findings exhibit fundamental insights into the pre-lithiation kinetics process for guiding the synthesis of high-quality singlecrystalline Ni-rich cathodes.

Effect of solution treatment on the microstructure,phase transformation behavior and functional properties of NiTiNb ternary shape memory alloys fabricated via laser powder bed fusion in-situ alloying

Post-heat treatment is commonly employed to improve the microstructural homogeneity and enhance the mechanical performances of the additively manufactured metallic materials.In this work,a ternary(NiTi)91Nb9(at.%)shape memory alloy was produced by laser powder bed fusion(L-PBF)using pre-alloyed NiTi and elemental Nb powders.The effect of solution treatment on the microstructure,phase transformation behavior and mechanical/functional performances was investigated.The in-situ alloyed(NiTi)91Nb9 alloy exhibits a submicron cellular-dendritic structure surrounding the supersaturated B2-NiTi matrix.Upon high-temperature(1273 K)solution treatment,Nb-rich precipitates were precipitated from the supersaturated matrix.The fragmentation and spheroidization of the NiTi/Nb eutectics occurred during solution treatment,leading to a morphological transition from mesh-like into rod-like and sphere-like.Coarsening of theβ-Nb phases occurred with increasing holding time.The martensite transformation temperature increases after solution treatment,mainly attributed to:(i)reduced lattice distortion due to the Nb expulsion from the supersaturated B2-NiTi,and(ii)the Ti expulsion from theβ-Nb phases that lowers the ratio Ni/Ti in the B2-NiTi matrix,which resulted from the microstructure changes from non-equilibrium to equilibrium state.The thermal hysteresis of the solutionized alloys is around 145 K after 20%pre-deformation,which is comparable to the conventional NiTiNb alloys.A short-term solution treatment(i.e.at 1273 K for 30 min)enhances the ductility and strength of the as-printed specimen,with the increase of fracture stress from(613±19)MPa to(781±20)MPa and the increase of fracture strain from(7.6±0.1)%to(9.5±0.4)%.Both the as-printed and solutionized samples exhibit good tensile shape memory effects with recovery rates>90%.This work suggests that post-process heat treatment is essential to optimize the microstructure and improve the mechanical performances of the L-PBF in-situ alloyed parts.

A Privacy Preservation Method for Attributed Social Network Based on Negative Representation of Information

Due to the presence of a large amount of personal sensitive information in social networks,privacy preservation issues in social networks have attracted the attention of many scholars.Inspired by the self-nonself discrimination paradigmin the biological immune system,the negative representation of information indicates features such as simplicity and efficiency,which is very suitable for preserving social network privacy.Therefore,we suggest a method to preserve the topology privacy and node attribute privacy of attribute social networks,called AttNetNRI.Specifically,a negative survey-based method is developed to disturb the relationship between nodes in the social network so that the topology structure can be kept private.Moreover,a negative database-based method is proposed to hide node attributes,so that the privacy of node attributes can be preserved while supporting the similarity estimation between different node attributes,which is crucial to the analysis of social networks.To evaluate the performance of the AttNetNRI,empirical studies have been conducted on various attribute social networks and compared with several state-of-the-art methods tailored to preserve the privacy of social networks.The experimental results show the superiority of the developed method in preserving the privacy of attribute social networks and demonstrate the effectiveness of the topology disturbing and attribute hiding parts.The experimental results show the superiority of the developed methods in preserving the privacy of attribute social networks and demonstrate the effectiveness of the topological interference and attribute-hiding components.

Data-Driven Learning Control Algorithms for Unachievable Tracking Problems

For unachievable tracking problems, where the system output cannot precisely track a given reference, achieving the best possible approximation for the reference trajectory becomes the objective. This study aims to investigate solutions using the Ptype learning control scheme. Initially, we demonstrate the necessity of gradient information for achieving the best approximation.Subsequently, we propose an input-output-driven learning gain design to handle the imprecise gradients of a class of uncertain systems. However, it is discovered that the desired performance may not be attainable when faced with incomplete information.To address this issue, an extended iterative learning control scheme is introduced. In this scheme, the tracking errors are modified through output data sampling, which incorporates lowmemory footprints and offers flexibility in learning gain design.The input sequence is shown to converge towards the desired input, resulting in an output that is closest to the given reference in the least square sense. Numerical simulations are provided to validate the theoretical findings.

Novel Sum-of-Sinusoids Simulation Channel Modeling for 6G Multiple-Input Multiple-Output Vehicle-to-Everything Communications

In this paper,a statistical cluster-based simulation channel model with a finite number of sinusoids is proposed for depicting the multiple-input multiple-output(MIMO)communications in vehicleto-everything(V2X)environments.In the proposed sum-of-sinusoids(SoS)channel model,the waves that emerge from the transmitter undergo line-of-sight(LoS)and non-line-of-sight(NLoS)propagation to the receiver,which makes the model suitable for describing numerous V2X wireless communication scenarios for sixth-generation(6G).We derive expressions for the real and imaginary parts of the complex channel impulse response(CIR),which characterize the physical propagation characteristics of V2X wireless channels.The statistical properties of the real and imaginary parts of the complex CIRs,i.e.,autocorrelation functions(ACFs),Doppler power spectral densities(PSDs),cross-correlation functions(CCFs),and variances of ACFs and CCFs,are derived and discussed.Simulation results are generated and match those predicted by the underlying theory,demonstrating the accuracy of our derivation and analysis.The proposed framework and underlying theory arise as an efficient tool to investigate the statistical properties of 6G MIMO V2X communication systems.

Simulation of space heavy-ion induced primary knock-on atoms in bipolar devices

Bipolar junction transistors(BJTs) are often used in spacecraft due to their excellent working characteristics. However,the complex space radiation environment induces primary knock-on atoms(PKAs) in BJTs through collisions, resulting in hard-to-recover displacement damage and affecting the performance of electronic components. In this paper, the properties of PKAs induced by typical space heavy ions(C, N, O, Fe) in BJTs are investigated using Monte Carlo simulations. The simulated results show that the energy spectrum of ion-induced PKAs is primarily concentrated in the low-energy range(17eV–100eV) and displays similar features across all tested ions. The PKAs induced by the collision of energetic ions have large forward scattering angles, mainly around 88°. Moreover, the distribution of PKAs within a transistor as a function of depth displays a peak characteristic, and the peak position is linearly proportional to the incident energy at a certain energy range. These simulation outcomes serve as crucial theoretical support for long-term semiconductor material defect evolution and ground testing of semiconductor devices.

Reliable ferroelectricity down to cryogenic temperature in wakeup free Hf_(0.5)Zr_(0.5)O_(2)thin films by thermal atomic layer deposition

The performance and reliability of ferroelectric thin films at temperatures around a few Kelvin are critical for their application in cryo-electronics.In this work,TiN/Hf_(0.5)Zr_(0.5)O_(2)/TiN capacitors that are free from the wake-up effect are investigated systematically from room temperature(300 K)to cryogenic temperature(30 K).We observe a consistent decrease in permittivity(εr)and a progressive increase in coercive electric field(Ec)as temperatures decrease.Our investigation reveals exceptional stability in the double remnant polarization(2P_(r))of our ferroelectric thin films across a wide temperature range.Specifically,at 30 K,a 2P_(r)of 36μC/cm^(2)under an applied electric field of 3.0 MV/cm is achieved.Moreover,we observed a reduced fatigue effect at 30 K in comparison to 300 K.The stable ferroelectric properties and endurance characteristics demonstrate the feasibility of utilizing HfO_(2)based ferroelectric thin films for cryo-electronics applications.

Continuous-Time Channel Prediction Based on Tensor Neural Ordinary Differential Equation

Channel prediction is critical to address the channel aging issue in mobile scenarios.Existing channel prediction techniques are mainly designed for discrete channel prediction,which can only predict the future channel in a fixed time slot per frame,while the other intra-frame channels are usually recovered by interpolation.However,these approaches suffer from a serious interpolation loss,especially for mobile millimeter-wave communications.To solve this challenging problem,we propose a tensor neural ordinary differential equation(TN-ODE)based continuous-time channel prediction scheme to realize the direct prediction of intra-frame channels.Specifically,inspired by the recently developed continuous mapping model named neural ODE in the field of machine learning,we first utilize the neural ODE model to predict future continuous-time channels.To improve the channel prediction accuracy and reduce computational complexity,we then propose the TN-ODE scheme to learn the structural characteristics of the high-dimensional channel by low-dimensional learnable transform.Simulation results show that the proposed scheme is able to achieve higher intra-frame channel prediction accuracy than existing schemes.

Analysis and Optimization of the Electrohydraulic Forming Process of Sinusoidal Corrugation Tubes

Aluminum alloy thin-walled structures are widely used in the automotive industry due to their advantages related to light weight and crashworthiness.They can be produced at room temperature by the electrohydraulic forming process.In the present study,the influence of the related parameters on the forming quality of a 6063 aluminum alloy sinusoidal corrugation tube has been assessed.In particular,the orthogonal experimental design(OED)and central composite design(CCD)methods have been used.Through the range analysis and variance analysis of the experimental data,the influence degree of wire diameter(WD)and discharge energy(DE)on the forming quality was determined.Multiple regression analysis was performed using the response surface methodology.A prediction model for the attaching-die state coefficient was established accordingly.The following optimal arrangement of parameters was obtained(WD=0.759 mm,DE=2.926 kJ).The attaching-die state coefficient reached the peak value of 0.001.Better optimized wire diameter and discharge energy for a better attaching-die state could be screened by CCD compared with OED.The response surface method in CCD was more suitable for the design and optimization of the considered process parameters.

闭孔率及密度对聚氨酯弹性体泡沫力学性能及吸能性的影响

聚氨酯弹性体泡沫同时具备泡沫类及弹性体类材料性能,可作为高效的减振吸能材料应用于防撞击装备领域。文中制备了不同闭孔率及密度的聚氨酯弹性体泡沫,通过红外光谱分析、扫描电镜及应变率为1000~4000s^(-1)的压缩性能测试等,探索了材料密度、泡孔结构、应变率对应力-应变曲线及吸能性的影响。发现聚氨酯弹性体泡沫的应力及单位体积吸能量随着密度、应变率及闭孔率的增加而增加。通过研究任意给定加载速率条件下闭孔率高的聚氨酯弹性体泡沫的能量吸收图,描述了不同密度材料在压缩冲击载荷下的特性,表明了在给定的加载条件下最优吸能聚氨酯弹性体泡沫密度为400 kg/m^(3)。其研究对于深入理解不同微观结构及密度的聚氨酯弹性体泡沫的吸能机理及应变率依赖性行为有重要意义,对聚氨酯弹性体泡沫作为优越的抗冲击吸能材料的实际工程应用提供了理论支持。

从燃烧热测量求算化学反应热——“燃烧热的测定”实验改进

经典物理化学实验“燃烧热的测定”主要涉及化学热力学中燃烧热知识点,为典型的验证性实验。本实验改进结合重要化学品邻苯二甲酸(酐)的生产过程,通过测量萘、邻二甲苯、邻苯二甲酸和邻苯二甲酸酐等几种物质的燃烧热,计算其合成过程的反应热,既丰富了燃烧热实验的内容,又能和实际应用相关联。实验涉及几种原料廉价易得,均可测得准确的燃烧热数值,进而能获得可靠的反应热结果。采用线上、线下相结合的翻转学习教学模式,再通过几个反应过程测量的分工合作,可以有效地培养和提升学生的自主学习能力和团队协作精神。

A geraniol synthase regulates plant defense via alternative splicing in tea plants

Geraniol is an important contributor to the pleasant floral scent of tea products and one of the most abundant aroma compounds in tea plants;however,its biosynthesis and physiological function in response to stress in tea plants remain unclear.The proteins encoded by the full-length terpene synthase(CsTPS1)and its alternative splicing isoform(CsTPS1-AS)could catalyze the formation of geraniol when GPP was used as a substrate in vitro,whereas the expression of CsTPS1-AS was only significantly induced by Colletotrichum gloeosporioides and Neopestalotiopsis sp.infection.Silencing of CsTPS1 and CsTPS1-AS resulted in a significant decrease of geraniol content in tea plants.The geraniol content and disease resistance of tea plants were compared when CsTPS1 and CsTPS1-AS were silenced.Down-regulation of the expression of CsTPS1-AS reduced the accumulation of geraniol,and the silenced tea plants exhibited greater susceptibility to pathogen infection than control plants.However,there was no significant difference observed in the geraniol content and pathogen resistance between CsTPS1-silenced plants and control plants in the tea plants infected with two pathogens.Further analysis showed that silencing of CsTPS1-AS led to a decrease in the expression of the defense-related genes PR1 and PR2 and SA pathway-related genes in tea plants,which increased the susceptibility of tea plants to pathogens infections.Both in vitro and in vivo results indicated that CsTPS1 is involved in the regulation of geraniol formation and plant defense via alternative splicing in tea plants.The results of this study provide new insights into geraniol biosynthesis and highlight the role of monoterpene synthases in modulating plant disease resistance via alternative splicing.

Vector Approximate Message Passing with Sparse Bayesian Learning for Gaussian Mixture Prior

Compressed sensing(CS)aims for seeking appropriate algorithms to recover a sparse vector from noisy linear observations.Currently,various Bayesian-based algorithms such as sparse Bayesian learning(SBL)and approximate message passing(AMP)based algorithms have been proposed.For SBL,it has accurate performance with robustness while its computational complexity is high due to matrix inversion.For AMP,its performance is guaranteed by the severe restriction of the measurement matrix,which limits its application in solving CS problem.To overcome the drawbacks of the above algorithms,in this paper,we present a low complexity algorithm for the single linear model that incorporates the vector AMP(VAMP)into the SBL structure with expectation maximization(EM).Specifically,we apply the variance auto-tuning into the VAMP to implement the E step in SBL,which decrease the iterations that require to converge compared with VAMP-EM algorithm when using a Gaussian mixture(GM)prior.Simulation results show that the proposed algorithm has better performance with high robustness under various cases of difficult measurement matrices.

In Situ Directional Polymerization of Poly(1,3-dioxolane)Solid Electrolyte Induced by Cellulose Paper-Based Composite Separator for Lithium Metal Batteries

In traditional in situ polymerization preparation for solid-state electrolytes,initiators are directly added to the liquid precursor.In this article,a novel cellulose paper-based composite separator is fabricated,which employs alumina as the inorganic reinforcing material and is loaded with polymerization initiator aluminum trifluoromethanesulfonate.Based upon this,a separator-induced in situ directional polymerization technique is demonstrated,and the extra addition of initiators into liquid precursors is no longer required.The polymerization starts from the surface and interior of the separator and extends outward with the gradually dissolving of initiators into the precursor.Compared with its traditional counterpart,the separator-induced poly(1,3-dioxolane)electrolyte shows improved interfacial contact as well as appropriately mitigated polymerization rate,which are conducive to practical applications.Electrochemical measurement results show that the prepared poly(1,3-dioxolane)solid electrolyte possesses an oxidation potential up to 4.4 V and a high Li+transference number of 0.72.After 1000 cycles at 2 C rate(340 mA g^(−1)),the assembled Li||LiFePO_(4)solid battery possesses a 106.8 mAh g^(−1)discharge capacity retention and 83.5%capacity retention ratio,with high average Coulombic efficiency of 99.5%achieved.Our work may provide new ideas for the design and application of in situ polymerization technique for solid electrolytes and solid batteries.

Twin model-based fault detection and tolerance approach for in-core self-powered neutron detectors

The in-core self-powered neutron detector(SPND)acts as a key measuring device for the monitoring of parameters and evaluation of the operating conditions of nuclear reactors.Prompt detection and tolerance of faulty SPNDs are indispensable for reliable reactor management.To completely extract the correlated state information of SPNDs,we constructed a twin model based on a generalized regression neural network(GRNN)that represents the common relationships among overall signals.Faulty SPNDs were determined because of the functional concordance of the twin model and real monitoring sys-tems,which calculated the error probability distribution between the model outputs and real values.Fault detection follows a tolerance phase to reinforce the stability of the twin model in the case of massive failures.A weighted K-nearest neighbor model was employed to reasonably reconstruct the values of the faulty signals and guarantee data purity.The experimental evaluation of the proposed method showed promising results,with excellent output consistency and high detection accuracy for both single-and multiple-point faulty SPNDs.For unexpected excessive failures,the proposed tolerance approach can efficiently repair fault behaviors and enhance the prediction performance of the twin model.

Stable sodium anodes for sodium metal batteries(SMBs) enabled by in-situ formed quasi solid-state polymer electrolyte

A high-performance quasi-solid polymer electrolyte for sodium metal batteries(SMBs)based on in-situ polymerized poly(1,3-dioxolane)(DOL)with 20%volume ratio of fluoroethylene carbonate(FEC),termed"PDFE-20",is proposed in this work.It is demonstrated PDFE-20 possesses a room-temperature ionic conductivity of 3.31×10^(-3) S cm^(-1),an ionic diffusion activation energy of 0.10 eV,and an oxidation potential of 4.4 V.SMBs based on PDFE-20 and Na_(3)V_(2)(PO_(4))_(3)(NVP)cathodes were evaluated with an active material mass loading of 6.8 mg cm^(-2).The cell displayed an initial discharge specific capacity of 104 mA h g^(-1),and97.1%capacity retention after 100 cycles at 0.5 C.In-situ polymerization conformally coats the anode/-cathode interfaces,avoiding geometrical gaps and high charge transfer resistance with ex-situ polymerization of the same chemistry.FEC acts as a plasticizer during polymerization to suppress crystallization and significantly improves ionic transport.During battery cycling FEC promotes mechanical congruence of electrolyte-electrode interfaces while forming a stable NaF-rich solid electrolyte interphase(SEI)at the anode.Density functional theory(DFT)calculations were also performed to further understand the role FEC in the poly(DOL)-FEC electrolytes.This work broadens the application of in-situ prepared poly(DOL)electrolytes to sodium storage and demonstrates the crucial role of FEC in improving the electrochemical performance.

碳纳米管对复合材料耐湿热老化过程的健康监测

基于电阻法和声发射方法对三相复合材料在湿热环境中的老化过程进行了健康监测,试件的电阻变化率与吸湿率之间呈现接近线性的关系,这为基于电阻法对材料提供健康监测打下了基础。比较了不同碳纳米管含量时声发射和电阻法对健康监测的效果后发现,当碳纳米管含量在0.2%和0.5%时,声发射相比电阻法来说,其变化幅度更接近于材料力学性能的变化幅度;而当碳纳米管含量为1%和2%时,相较于声发射法,电阻法则更加适合用于健康监测。

Lowering the threshold of alanine aminotransferase for enhanced identification of significant hepatic injury in chronic hepatitis B patients

BACKGROUND The clinical and histological features of chronic hepatitis B(CHB)patients who fall into the"grey zone(GZ)"and do not fit into conventional natural phases are unclear.AIM To explore the impact of varying the threshold of alanine aminotransferase(ALT)levels in identifying significant liver injury among GZ patients.METHODS This retrospective analysis involved a cohort of 1617 adult patients diagnosed with CHB who underwent liver biopsy.The clinical phases of CHB patients were determined based on the European Association for the Study of the Liver 2017 Clinical Practice Guidelines.GZ CHB patients were classified into four groups:GZ-A(HBeAg positive,normal ALT levels,and HBV DNA≤10^(7) IU/mL),GZ-B(HBeAg positive,elevated ALT levels,and HBV DNA<10^(4) or>10^(7) IU/mL),GZC(HBeAg negative,normal ALT levels,and HBV DNA≥2000 IU/mL),and GZ-D(HBeAg negative,elevated ALT levels,and HBV DNA≤2000 IU/mL).Significant hepatic injury(SHI)was defined as the presence of notable liver inflammation(≥G2)and/or significant fibrosis(≥S2).RESULTS The results showed that 50.22%of patients were classified as GZ,and 63.7%of GZ patients developed SHI.The study also found that lowering the ALT treatment thresholds to the American Association for the Study of Liver Diseases 2018 treatment criteria(35 U/L for men and 25 U/L for women)can more accurately identify patients with significant liver damage in the GZ phases.In total,the proportion of patients with ALT≤40 U/L who required antiviral therapy was 64.86%[(221+294)/794].When we lowered the ALT treatment threshold to the new criteria(30 U/L for men and 19 U/L for women),the same outcome was revealed,and the proportion of patients with ALT≤40 U/L who required antiviral therapy was 75.44%[(401+198)/794].Additionally,the proportion of SHI was 49.1%in patients under 30 years old and increased to 55.3%in patients over 30 years old(P=0.136).CONCLUSION These findings suggest the importance of redefining the natural phases of CHB and using new ALT treatment thresholds for better diagnosis and management of CHB patients in the GZ phases.

Technique of using Cionni-modified capsular tension ring in the management of severely traumatic lens subluxation

AIM:To investigate the effect of Cionni-modified capsular tension ring(CTR)implantation in patients with severely traumatic subluxated cataracts.METHODS:All patients who totally had traumatic cataracts and lost zonule support and underwent cataract surgery were retrospectively analyzed.Corrected distance visual acuity(CDVA),extent of zonulysis,intraocular lens(IOL)position,intraoperative presentation,and complications were assessed.The primary outcomes included IOL centration stability and other postoperative complications.RESULTS:Twenty patients(20 eyes)were included in this study.The mean age in this study was 58.0±11.3y,and the average follow-up time was 17.3±12.8mo.Capsule bags were saved by Cionni-modified CTR.Nine eyes(45%)underwent simultaneously anterior vitrectomy due to the presence of vitreous in the anterior chamber.The preoperative mean CDVA was 0.83±0.24 log MAR,and the postoperative average CDVA was 0.23±0.30 log MAR(P<0.05).The horizontal and vertical IOL decentration after surgery was 0.27±0.12 mm and 0.41±0.19 mm,respectively;the vertical and horizontal IOL tilt after surgery was 5.5°±2.5°and 6.1°±2.2°,respectively.None of the eyes had obvious IOL decentration during the follow-up time.Eight eyes(40%)had posterior capsule opacification(PCO)that was severe enough to cause poor vision.Neodymium:YAG laser capsulotomy were performed on these eyes when the CTR was stabilized.CONCLUSION:With the help of Cionni-modified CTR,capsular bag preservation and better IOL concentration can be achieved without major complications in patients with severely traumatic subluxated cataracts.