锥形量热法研究木质素基膨胀型阻燃剂对环氧树脂阻燃抑烟效果

以来自自然界储量第二的木质素作为膨胀型阻燃剂的基体,通过接枝氮、磷元素成功合成碳源、酸源、气源三位一体的木质素基膨胀型阻燃剂（Lig-T）,实现了良好的阻燃性能。将Lig?T按照不同含量添加到环氧树脂（EP）中制备EP/Lig-T复合材料,以锥形量热测试考察复合材料的热稳定性能和阻燃性能,并重点考察复合材料在接近真实火灾事故时的热释放和烟释放规律。结果表明,当Lig-T含量为20 %（质量分数,下同）时,复合材料的热释放速率峰值为1 374 kW/m²、热释放总量为41.63 MJ/m²、烟释放总量为1 634 m²/m²,与EP参比试样的数值相比,均呈现下降的趋势,燃烧结束的残炭率从4.26 %增至10.01 %。基于气相和凝聚相的协效阻燃机理,木质素作为膨胀型阻燃剂的碳源使得复合材料在高温条件下具备更好的成炭效果,在燃烧过程中形成稳定且致密的炭层结构,在实现高效阻燃的同时减少有毒烟气的释放,降低火灾的危害。     

Imaging and structural feature decomposition of a complex target using multi-aspect polarimetric scattering

Based on the Huynen parametric decomposition of target scattering matrix, the polarimetric ellipse parameters are transformed and applied to decomposition of scattering mechanisms of a complex target in VHR POL-SAR images (very high resolution, polarimetric synthetic aperture radar). Making use of multi-aspect (or circle-aspect) and wideband VHR POL-SAR images, scattering mechanisms of a volumetric target and its structural components are recognized over image pixels. Utilizing the layover features, the target height profile is also estimated from two-dimensional image. As example, polarimetric scattering data of some vehicles on ground, including multi-aspect simulated data and experimental measurements, are applied to validations of scattering mechanism decompositions and target structural feature recognition.     

分形下的河道演变初探——以尼洋河为例

以尼洋河为例运用分形算法探讨了河道演变的机理,初步认为:在河道演变分类的基础上,河道演变是河道外部条件和河道内部条件不断协调的结果,即演变主要依靠水力和携砂两个关键因素。具体到尼洋河来说是渐进式演变与急剧式演变相结合的河道演变,其渐进式演变主要由于携砂带来河势演变,其急剧式演变主要是由于水位落差或流量增大引起的纵向和横向演变。     

Nano functional neural interfaces

Engineered functional neural interfaces (fNIs) serve as essential abiotic–biotic transducers between an engineered system and the nervous system. They convert external physical stimuli to cellular signals in stimulation mode or read out biological processes in recording mode. Information can be exchanged using electricity, light, magnetic fields, mechanical forces, heat, or chemical signals. fNIs have found applications for studying processes in neural circuits from cell cultures to organs to whole organisms. fNI-facilitated signal transduction schemes, coupled with easily manipulable and observable external physical signals, have attracted considerable attention in recent years. This enticing field is rapidly evolving toward miniaturization and biomimicry to achieve long-term interface stability with great signal transduction efficiency. Not only has a new generation of neuroelectrodes been invented, but the use of advanced fNIs that explore other physical modalities of neuromodulation and recording has begun to increase. This review covers these exciting developments and applications of fNIs that rely on nanoelectrodes, nanotransducers, or bionanotransducers to establish an interface with the nervous system. These nano fNIs are promising in offering a high spatial resolution, high target specificity, and high communication bandwidth by allowing for a high density and count of signal channels with minimum material volume and area to dramatically improve the chronic integration of the fNI to the target neural tissue. Such demanding advances in nano fNIs will greatly facilitate new opportunities not only for studying basic neuroscience but also for diagnosing and treating various neurological diseases.     

变硬度组合式汽车座椅设计与舒适性分析

针对驾乘人员和汽车座椅之间接触压力分布不均匀的现象,设计了一种由不同硬度海绵材料制成的变硬度组合式汽车座椅,使汽车座椅海绵材料的力学特性适应体压分布的特点。利用压力传感器测量得到人体与汽车座椅之间的接触压力分布图像,并进行了仿真分析,对不同汽车座椅的试验数据进行平滑处理后进行对比分析。提出了理想压强差的概念,通过比较汽车座椅断面上的压力分布与理想体压分布曲线的贴合程度,实现对汽车座椅乘坐舒适性的定量分析。结果表明组合式汽车座椅可以在一定程度上提高乘坐舒适性。     

CO2 sequestration in depleted methane hydrate deposits with excess water

The recent increase in atmospheric CO₂ concentration makes it necessary to investigate new ways to reduce CO₂ emissions. Simultaneously, natural gas hydrate mining technology is developing rapidly. The use of depleted methane hydrate (MH) deposits as potential sites for CO₂ storage is relatively safe and economical. This method can alleviate the shortage of hydrate displacement gas with CO₂. The purpose of this study was to investigate CO₂ hydrate formation characteristics during the seepage process—in reservoirs with excess water—and their effect on CO₂ storage. The experimental process can be divided into 5 parts: MH formation, water injection, MH dissociation, CO₂ hydrate formation, and CO₂ hydrate dissociation. Magnetic resonance imaging was employed to monitor the distribution of liquid water, and the effects of different parameters on the formation and dissociation of CO₂ hydrates were analyzed. It was found that a state of initial water saturation can effectively control hydrate saturation in artificial MH reservoirs for hydrate reservoirs with excess gas. In the process of CO₂ flow, initial water saturation was not the main controlling factor for CO₂ hydrate formation. Increasing the flow pressure and reducing the flow rate were beneficial for CO₂ hydrate formation. This study is of great significance for advancing the science of CO₂ geological storage in the form of deep‐sea hydrates.     

乙烯装置裂解气压缩机开车过程动态模拟

裂解气压缩机作为乙烯装置的核心设备,其顺利启动对乙烯装置开车过程有着重要影响.传统的乙烯装置开车流程大多使用裂解气启动压缩机,近年来已经逐步被氮气、天然气和混合烃等开车工质取代.由于无法利用实际压缩机装置进行测试,因此化工模拟技术成为了解决上述问题的重要工具.本文根据"稳态-动态-开车"的研究方法,建立了某裂解气压缩机的稳态模拟模型,确定了氮气、混合烃和裂解气运行时的稳态运行参数.之后,将稳态模型转换为动态模型,通过动态模拟验证了各工况之间转换过程的安全性和可行性.     

Yb:YAG absorption at ambient and cryogenic temperatures

We have performed absorption measurements and generated absorption cross sections as a function of wavelength for the laser material YAG doped with ytterbium at 300, 175, and 75 K. This data was generated to enable a direct comparison of the absorption intensity and linewidths at room and cryogenic temperatures, and in particular near the temperature of liquid nitrogen at 77 K. The data have been used to compute universal absorption contour plots that display absorption as a function of the incident light center wavelength and optical thickness (doping density times penetration depth) for a number of bandwidths, and assuming that the spectrum of the incident light can be described as a Gaussian. Curves are presented for both 300 and 75 K, and may be used to optimize the absorption and laser efficiency.     

梯形齿同步带齿向载荷分布系数K_β的计算方法的研究

本文把带齿受载情况处理成由许多薄片叠成的力学模型,根据带齿失准度f_β、刚度C、平均载荷F_m/b及带传动基本参数计算出齿向载荷分布系数K_β。文中还简要介绍了带齿失准度f_β的确定方法。     

我国蔬菜种业发展战略研究

我国是世界第一大蔬菜生产国与消费国,蔬菜种业是确保现代蔬菜产业发展和蔬菜周年均衡供应的重要物质基础。实现蔬菜种业的可持续发展要靠科技创新。我国蔬菜种业发展进入了一个关键的时期。本文分析了我国蔬菜种业与种业科技的现状,对比了国外蔬菜种业发展的情况,针对我国蔬菜种业的主要问题,提出了我国蔬菜种业的发展战略、目标、任务、保障措施和政策建议。