An Equivalent Substitute Strategy for Constructing 3D Ordered Porous Carbon Foams and Their Electromagnetic Attenuation Mechanism

Three-dimensional(3D)ordered porous carbon is generally believed to be a promising electromagnetic wave(EMW)absorbing material.However,most research works targeted performance improvement of 3D ordered porous carbon,and the specific attenuation mechanism is still ambiguous.Therefore,in this work,a novel ultra-light egg-derived porous carbon foam(EDCF)structure has been successfully constructed by a simple carbonization combined with the silica microsphere template-etching process.Based on an equivalent substitute strategy,the influence of pore volume and specific surface area on the electromagnetic parameters and EMW absorption properties of the EDCF products was confirmed respectively by adjusting the addition content and diameter of silica microspheres.As a primary attenuation mode,the dielectric loss originates from the comprehensive effect of conduction loss and polarization loss in S-band and C band,and the value is dominated by polarization loss in X band and Ku band,which is obviously greater than that of conduction loss.Furthermore,in all samples,the largest effective absorption bandwidth of EDCF-3 is 7.12 GHz under the thickness of 2.13 mm with the filling content of approximately 5 wt%,covering the whole Ku band.Meanwhile,the EDCF-7 sample with optimized pore volume and specific surface area achieves minimum reflection loss(RL_(min))of−58.08 dB at 16.86 GHz while the thickness is 1.27 mm.The outstanding research results not only provide a novel insight into enhancement of EMW absorption properties but also clarify the dominant dissipation mechanism for the porous carbon-based absorber from the perspective of objective experiments.

Wave attenuation mechanism of cross-plates applied in landslide-induced tsunami in river course

Since the impounding of the Three Gorges Reservoir, the channel of the Yangtze River has become a busy watercourse and the probability of landslide-induced tsunamis has increased. In the case of landslide-induced tsunamis in the Three Gorges Reservoir, even after shipping closures in advance, there are still facilities and objects in urgent need of protection within the risk zone of the watercourse, such as wharfs, marine fueling stations, berthed ships. The emergency protection against and decay of landslide-induced tsunamis in inland watercourses is a new challenge. In this study, 37 sets of wave decay experiments were conducted with the hydromechanics numerical method. The wave decay efficiencies of common simple structures including submerged horizontal plate, horizontal plate on the water surface, inclined thin plate and cross-plates in coastal areas were compared and analyzed. Cross-plates structure showed better wave decay capacity than other simple plates. The wave decay performance of cross-plates was related to five modes of energy dissipation and transformation, namely run-up/run-down, overtopping, reflecting, return flow and disturbed wave orbital path. The type of wave had little relation with the decay performance of cross-plates, but a strong correlation with cross-plates structure, especially the height of the vertical emerged plate. The best decay performance was observed when the ratio of wave amplitude to emerged vertical plate height was between 1 and 1.5, which can reduce up to about 8o% of the incoming wave amplitude. Finally, the emergency way of cross-plates applied to the decay of landslide-induced tsunami in river course is discussed. This study provides a conceptual reference for related studies to practice the attenuation of landslide-induced tsunami in reservoirs.

Robust stabilization and disturbance attenuation for a class of underactuated mechanical systems

The robust control problem for a class of underactuated mechanical systems called acrobots is addressed. The goal is to drive the acrobots away from the straight-down position and balance them at the straight-up unstable equilibrium position in the presence of parametric uncertainties and external disturbance. First, in the swing-up area, it is shown that the time derivative of energy is independent of the parameter uncertainties, but exogenous disturbance may destroy the characteristic of increase in mechanical energy. So, a swing-up controller with compensator is designed to suppress the influence of the disturbance. Then, in the attractive area, the control problem is formulated into a H~ control framework by introducing a proper error signal, and a sufficient condition of the existence of Hoo state feedback control law based on linear matrix inequality （LMI） is proposed to guarantee the quadratic stability of the control system. Finally, the simulation results show that the proposed control approach can simultaneously handle a maximum ±10% parameter perturbation and a big disturbance simultaneously.

Relationships of the internodal distance of biological tissue with its sound velocity and attenuation at high frequency in doublet mechanics

In view of the discrete characteristics of biological tissue, doublet mechanics has demonstrated its advantages in the mathematic description of tissue in terms of high frequency （〉 10 MHz） ultrasound. In this paper, we take human breast biopsies as an example to study the influence of the internodal distance, a microscope parameter in biological tissue in doublet mechanics, on the sound velocity and attenuation by numerical simulation. The internodal distance causes the sound velocity and attenuation in biological tissue to change with the increase of frequency. The magnitude of such a change in pathological tissue is distinctly different from that in normal tissue, which can be used to differentiate pathological tissue from normal tissue and can depict the diseased tissue structure by obtaining the sound and attenuation distribution in the sample at high ultrasound frequency. A comparison of sensitivity between the doublet model and conventional continuum model is made, indicating that this is a new method of characterizing ultrasound tissue and diagnosing diseases.

Attenuation coefficients of gamma and X-rays passing through six materials

The aim of this study was to determine the attenuation of gamma and X-rays with different energies caused by passage through different materials.To this end,different materials with a range of atomic numbers were chosen to measure gamma and X-ray attenuation coefficients and to explore the mechanisms of interaction of gamma and X-rays with matter of various kinds.It is shown that the attenuation coefficients first decrease and then increase with increase in the radiation(photon)energy.The attenuation of gamma and X-rays passing through materials with high atomic number is greater than that in materials with low atomic number.The attenuation minimum is related to the atomic number of the irradiated materials.The larger the atomic number is,the lower the energy corresponding to attenuation minimum is.Photoelectric and Compton effects are the main processes when gamma rays pass through individual materials with high and low atomic numbers,respectively.Therefore,for radiotherapy and radiation protection,different methods should be considered and selected for the use of gamma and X-rays of different energies for use in different materials.

Optimization of multiple attenuation mechanisms by cation substitution in imidazolic MOFs-derived porous composites for superior broadband electromagnetic wave absorption

Metal-organic frameworks(MOFs)derived composites are extremely potential electromagnetic wave(EMW)absorbers.However,the permittivity of absorbers directly derived from MOFs with solid structure is usually relatively low,inevitably limiting their further applications.Cation substitution can primely overcome the problem by regulating the morphology and atomic space occupation to enhance multiple loss mechanisms and impedance matching characteristics.However,universal mechanisms of the effect on EMW absorption performance influenced by cation substitution are still comparatively inadequate,which prospectively requires further exploration.Herein,a series of imidazolic MOFs were fabricated by ultrasonic symbiosis method and tailored by subsequent cation substitution strategy to prepare target porous composites.At a low filling rate and thin thickness,the as-obtained samples reach the optimal reflection loss and effective absorption bandwidth values of–49.81 dB and 7.63 GHz,respectively.The intercoupling between multiple atoms lays a significant foundation for abundant heterogeneous interfaces and defect vacancies,which effectively ameliorate the attenuation mechanisms.Meanwhile,the porous structure introduced by cation substitution reduces the bulk density to enhance the impedance matching and multiple reflections simultaneously.This study provides a helpful idea to exceedingly improve the EMW absorbing performance of imidazolic MOFs-derived composites by cation substitution.

Protein–membrane interactions investigated with surface-induced fluorescence attenuation

Research on protein-membrane interactions has been undeveloped due to the lack of proper techniques to detect the position of proteins at membranes because membranes are usually only about 4-nm thick. We have recently developed a new method named surface-induced fluorescence attenuation （SIFA） to track both vertical and lateral kinetics of a single labelling dye in supported lipid bilayers. It takes advantage of strong interaction between a light-emitting dye and a partially reflecting surface. By applying the technique to membrane proteins being fluorescently labelled at different residues, here we show that SIFA can measure not only the insertion depth of a dye inside a lipid bilayer, but also the position of a dye in solution near the surface. SIFA can therefore be used to study membrane proteins of various types.

A Kinetic Evidence for the Nitroxyl Radicals Recycling Mechanism in the Photostabilizing Process of HALS

The photoinduced bulk polymerization of a reactive-hindered amine light stabilizers (r-HALS), 4-acryloyl-2, 2, 6,6-tetramethylpiperidinyl (ATMP), was performed at 80 C by using a DPC technique. An unique periodic exponential attenuation-type oscillating curve was found when the polymerization was carried out in air, but this phenomenon was not found in nitrogen. It is supposed that this unique kinetic performance may be attributed to nitroxyl radicals that are produced in situ from the oxidation of ATMP. ATMP polymer with narrow polydispersity (d = 1.03) can be obtained by photoinduced solution polymerization of ATMP. The signal detected in ESR may be assigned to the nitroxyl radicals in the matrix of ATMP polymer. Since this kind of recycling of nitroxyl radicals is well documented for the photostabilizing mechanism of HALS, the present results may serve as a kinetic evidence for this mechanism.

盐冻循环作用下水泥稳定碎石混合料的宏细观性能

为研究盐分和冻融循环耦合侵蚀作用下水泥稳定碎石混合料的力学性能、疲劳特性及微细观空隙结构衰减规律,在冻融条件下对不同初始含盐量的水泥稳定碎石混合料开展无侧限抗压强度试验、弯拉强度试验、动态压缩模量试验和三分点加载疲劳试验。基于工业CT无损检测技术研究了盐冻耦合作用下水泥稳定碎石混合料微细观空隙结构衰减规律;提出了盐冻循环次数与盐溶液浓度对水泥稳定碎石混合料力学性能、疲劳性能和微细观空隙直径期望值的衰减公式;建立了微细观空隙结构与宏观力学性能、疲劳性能之间的拟合关系。结果表明:盐冻耦合侵蚀作用加速了水泥稳定碎石混合料力学性能与疲劳特性衰减,随着盐冻循环次数增加,水泥稳定碎石混合料的无侧限抗压强度与动态回弹模量呈指数模型衰减,弯拉强度与疲劳寿命呈三次函数模型衰减;盐冻损伤主要集中在集料边缘的原生空隙部位,微细观等效空隙直径期望值和空隙级配中小于0.1 mm3的空隙数量随着盐冻耦合侵蚀作用次数增加而增大;硫酸钠盐溶液浓度越大,经历相同盐冻循环后水泥稳定碎石混合料力学性能和疲劳性能损伤度越高,微细观等效空隙直径期望值随着硫酸钠盐溶液浓度增大呈线性关系增大;随着等效空隙直径期望值增大,水泥稳定碎石混合料的动态回弹模量、无侧限抗压强度和弯拉强度均呈线性关系减小,同时疲劳寿命呈指数函数关系降低;盐冻耦合侵蚀作用改变了水泥稳定碎石内部微细观空隙结构,是盐冻耦合侵蚀作用导致水泥稳定碎石混合料力学性能和疲劳性能下降的原因之一。

理肺解毒益髓汤对晚期肺癌化疗的增效减毒作用及其机制研究

目的:探究理肺解毒益髓汤对晚期肺癌化疗的增效减毒作用及其机制。方法:将2021年1月—2022年3月河北省中医院呼吸一科收治的80例晚期肺癌化疗患者依据随机数字表法分为对照组(n=40)和观察组(n=40)。对照组进行常规化疗,观察组则在对照组的基础上加用理肺解毒益髓汤。比较两组临床疗效、毒副反应发生率、治疗前后生存质量[健康调查量表36(SF-36)]、免疫因子[白细胞介素(IL)-4、IL-6、IL-10、IL-17及γ干扰素(IFN-γ)]及外周血循环肿瘤细胞数。结果:观察组总有效率显著高于对照组,毒副反应发生率均显著低于对照组,差异均有统计学意义(P<0.05);治疗前,两组SF-36评分、免疫因子及外周血循环肿瘤细胞数比较,差异均无统计学意义(P>0.05);治疗后观察组SF-36评分、IFN-γ水平均显著高于对照组,IL-4、IL-6、IL-10、IL-17均显著低于对照组,外周血循环肿瘤细胞数少于对照组,差异均有统计学意义(P<0.05)。结论:理肺解毒益髓汤在晚期肺癌化疗患者中的增效减毒作用突出,可显著改善患者的生存质量,可能是通过调节免疫因子发挥作用。

岩体中应力波传播衰减规律研究进展

为揭示地质构造变化或爆破等产生的应力波在不同影响因素条件的衰减机制,学者们借助位移不连续法和等效连续介质法等理论方法,针对完整传播过程的入射、传播和透射3个不同阶段,开展了应力波传播衰减规律影响的研究。研究结果表明波形、岩体性质和节理性质均会对其衰减特性产生显著影响。总结以上研究方法,讨论各方法之间的联系和异同点,在此基础上提出亟待解决的问题和研究方向,为充分了解应力波传播过程中的衰减变化规律、完善波动理论和提高实际工程安全性提供参考。

三枕捣固装置激扰下有砟轨道振动传递及衰减特性试验研究

大机非稳态捣固作业是新建铁路开通运营前的必备工序,目前尚无研究涉及三枕捣固装置激扰下有砟轨道的振动传递特性。针对此不足,选取某典型新建铁路,开展捣固作业过程中有砟轨道动力响应的现场大型原位试验,并在散体道床内部不同位置埋设自制的双轴振动加速度传感器,实现道床内部振动水平演变的实时监测。采用小波分析和快速傅里叶变换方法,从时域-频域角度探究了捣固作业过程中轨枕和道床的振动传递及衰减特征,对比分析不同捣固作业次数影响下有砟轨道的吸振能力和耗能特性。研究结果表明:捣固作业过程中存在典型的振动逆向传递现象,会降低道床的承载能力及稳定性;夹持阶段轨枕的主要响应频率为68.7 Hz,约为35 Hz捣镐固定振动频率的2倍;捣固作业过程中轨枕对不同方向振动的敏感程度存在显著差异,捣镐的横向振动分量会激发道床内部更加丰富的振动响应;第三次捣固作业过程中道床的振动水平较低,道砟颗粒破碎概率最小。因此建议在不改变捣固作业时间和其他捣固作业参数的条件下现场进行多次连续捣固作业时,作业次数不宜超过3次,以保证最佳捣固效果。

补骨脂肝毒性及其减毒方法的研究进展

补骨脂因含香豆素类、黄酮类和单萜酚类等化学成分,具有抗肿瘤、抗氧化、抗菌、抗炎、调节雌激素水平、促进骨生长、神经保护等作用而广泛用于肾部疾病、脾胃病、肢体经络病、妇科病的治疗,是临床常用的传统“无毒”的补益类中药,但近年来,国家药品不良反应监测中心多次通报警示补骨脂相关制剂(如壮骨关节丸、仙灵骨葆胶囊、致康胶囊)引发的肝损伤问题,更有单味补骨脂引发肝损伤的临床病例报道,其肝损伤现象已成为当前行业研究的热点及难点,为补骨脂的临床安全用药带来极大挑战。课题组前期基于脂多糖模型证实了补骨脂具有特异质肝损伤的属性,并从体内外角度相互验证了补骨脂甲素、补骨脂乙素、补骨脂酚、补骨脂定或可通过调控PI3K-Akt信号通路、NF-κB信号通路、NLRP3信号通路等引发肝损伤。通过对近年来补骨脂肝毒性的相关文献进行整理、归纳,探讨引起补骨脂肝毒性的主要毒理机制,并总结了配伍减毒和炮制减毒对减轻补骨脂肝毒性的重要意义,为补骨脂的临床安全用药提供数据支撑。

雷公藤血液毒性机制及防治的研究进展

雷公藤用药历史悠久,具有祛风除湿、活血化瘀、清热解毒等功效,常用于多种免疫系统疾病的治疗,疗效显著。作为一种传统有毒中药,其血液毒性也不容小觑,限制了其在很多领域的应用,也愈发受到广泛关注。通过综述雷公藤相关研究,梳理分析血液毒性表现特点发现,患者临床表现轻重不同,重者可能会产生骨髓抑制,但发生率低,且大多可逆。由于其所含化学成分复杂,不同成分致血液毒性产生的机制各异。对雷公藤所含有的主要毒性成分进行归类梳理,并从抑制细胞周期、影响转录调节、致突变及诱导细胞凋亡等方面总结其血液毒性作用机制,对雷公藤减毒的中西医防治措施进行整理与发掘,总结单味中药、中药复方及西药减毒机制,为其在临床的使用提供参考与依据。

钠离子电池用O3型层状金属氧化物研究进展

O3型层状金属氧化物具有理论容量高、制备简单等优势,是有前景实现商业化应用的钠离子电池正极材料之一。固有的缺点严重限制了层状金属氧化物正极的商业化进程,迫切需要解决。系统总结不可逆相变、表面侵蚀、产气等问题,分析比较固相法、共沉淀法和溶胶凝胶法等3种常用合成方法的优缺点,对O3型层状金属氧化物相关改性策略进行归纳,包括元素掺杂、表面包覆、混相设计和高熵设计等。

冻融循环及含水率对冰碛土力学特性影响

处在季节性冻土区的冰碛土受冻融循环作用影响显著,极大地影响工程的稳定和安全。为了探究冻融循环作用及初始含水率对冰碛土静力学特性的影响,以川西甘孜州海螺沟的冰碛土为研究对象,通过开展不同冻融循环次数及初始含水率条件下冰碛土不固结不排水三轴试验研究冻融循环作用对冰碛土力学参数的影响。试验结果表明:冻融循环作用下冰碛土应力-应变曲线为弱应变软化型;随冻融循环次数增加,冰碛土弹性模量、抗剪强度均呈现出先快速衰减后趋于稳定的变化趋势,且初始含水率越大其力学指标衰减程度越大,黏聚力呈负指数型函数降低,而内摩擦角无明显变化;采用指数型函数对抗剪强度、弹性模量试验值进行多元非线性拟合,建立冰碛土力学参数与围压、含水率及冻融循环次数的关系表达式,拟合效果理想,可用于推算经历冻融循环后土体力学参数值;冻融循环作用会使冰碛土力学性质显著劣化,且劣化程度与含水率呈正相关。研究成果可为高寒山区工程设计与建设提供科学支撑。

电池储能系统状态估计综述

为了提高多场景应用的技术经济性,本文对电池储能系统状态估计进行了综述。首先,分析了电池性能衰减的机理,介绍了目前常用的物理建模和数据建模方法,进而对荷电状态(state of charge,SOC)和健康状态(state of health,SOH)进行了定义与关联性分析,并对电池及其系统的状态估计方法进行了汇总;其次,为了获取更多精确的电池运行数据,重点介绍了能够刻画电池内部演化机理的原位/非原位表征技术,进而分析了嵌入式电池管理系统(battery management system,BMS)实际应用的主流开发路线;第三,提出了基于联邦学习的电池储能系统状态估计方法,基于轻量化模型在本地进行电池储能系统SOC的估计以保证控制实时性,基于大数据驱动策略在云中心进行其SOH估计以保证容量可信度,由此实现云边的交互与协同;最后,对电池储能系统未来可能的发展方向和研究重点进行了预测。研究结果表明:活性锂损失是锂离子电池容量衰退的主要原因,高温、低温、过充放等滥用也会加速电池性能衰减;数据驱动在电池系统级建模与状态评估方面具有较大优势;利用原位/非原位表征技术可以获取更多的电池内部状态数据,基于FPGA的BMS轻量化建模更易实现,基于联邦学习的状态评估方法能够提高电池储能系统的智慧化运维水平。

Radon变换频变自适应多次波压制方法

Radon变换是常用多次波压制方法之一,然而有限、离散的采样空间导致一次波和多次波在Radon域混叠,并且混叠程度随频率降低愈加严重.高分辨率Radon变换可以改善一次波和多次波分离效果,但分辨率的提高会降低保幅性,导致多次波残留或一次波损伤.为此,本文在最小二乘反演基础上,提出一种随混叠程度自适应分离多次波的频变滤波方法.根据Radon变换褶积模型,分析一次波和多次波频变混叠机制;建立随频率调整的修正柯西函数混叠模型;依据一次波和多次波的混叠比例设计多次波滤波器,该滤波器能够根据一次波和多次波的混叠程度自适应调整滤波函数,提高多次波估计精度.合成数据和实际数据的多次波压制实验表明,这种频变滤波方法既可以改善多次波压制效果,又可避免高分辨率反演方法计算量大的问题.

基于改进pix2pix GAN的多次波压制算法

有效压制地震多次波是地震资料处理过程中的重要环节,尽管已有多种多次波压制方法,但是传统的多次波压制方法依赖先验地质构造信息且需要大量的计算,导致多次波压制效率较低,对于复杂地质条件下的多次波压制更具挑战。为此,提出将改进pix2pix GAN运用于多次波压制问题中,利用神经网络的特征学习能力,提高多次压制波的精度。这种改进的pix2pix GAN结合ResNet与U-Net作为网络的生成器,以避免深层网络引起的梯度消失或梯度爆炸现象。并在生成器中引入SE注意力机制,改进的生成器能够更好的感知地震波中一次波与多次波的特征,提升生成器性能。此外,使用多尺度判别器对更精细的地震图像细节特征和纹理信息做出真假判别。网络的输入为全波场数据,标签为一次波数据,使用两个简单地层模型和一个公开的Sigbee2B模型合成的数据集训练网络。实验结果表明,改进的pix2pix GAN比pix2pix GAN的多次波压制效果更好;网络训练一旦完成,即可有效提升多次波压制速度。

轻微精神病综合征患者认知功能损害研究进展

轻微精神病综合征(attenuated psychosis syndrome,APS)是指具有高度精神病风险的临床障碍。该时期患者通常表现出多维度神经认知和社会认知功能受损。APS患者认知功能损害与额叶、颞叶及皮质下脑区的结构和功能异常有关。目前主要使用药物治疗、心理治疗、营养治疗和计算机认知训练提升APS患者的认知功能。未来可综合利用脑影像、电生理、分子影像等技术,深入探究APS认知功能损害神经病理机制,并结合计算机、虚拟现实、人工智能等技术,开发新型认知功能干预程序,以期实现APS精准防治。