Ablation behaviors and mechanism of ultra-thick anti-oxidation layer coating on carbon-bonded carbon fiber composites

To enhance the oxidation resistance capability of the carbon-bonded carbon fiber composites (CBCFs), a silicide ultra-thick coating as high as 1.6 mm with gradient structure is designed and fabricated via a multi-step rapid sintering method. Compared with other ceramic layers on carbon fiber-based composites, ultra-thick anti-oxidation layer coated-CBCFs have the lowest thermal conductivity. Additionally, ablation behaviors of the ultra-thick ceramics layer coated-CBCFs under the oxyacetylene torch are also investigated. After being exposed to oxyacetylene torch, the ultra-thick ceramics layer coated-CBCFs possess a linear rate range from 0.6 to 1.2 μm/s, while a mass ablation rate ranges from 4.95 × 10⁻⁵ g/m² s to 1.45 × 10⁻³ g/m² s.     

新传输层技术

未来应用的发展对网络能力提出了新的挑战，传输层作为衔接应用层和网络层的媒介，局限于本层提升网络资源利用率已无法满足未来应用的需求。以全息通信为背景，对未来网络传输的特征进行了分析，描述了新传输层面向未来应用需要具备的能力，提出了基于两级调度机制的多路传输层架构，为迎接未来应用对网络带来的挑战提供了灵活、可扩展的传输模型。     

Novel displacement function for discontinuous deformation analysis based on mean value coordinates

The rotation degree of freedom in discontinuous deformation analysis (DDA) may cause false volume expansion when a block undergoes a large rotation. We propose a block displacement function to prevent this defect. Specifically, the degrees of freedom in a block are redefined by incremental displacements at its vertices, and displacement is formulated based on the mean value coordinates. In addition, the finite element method with updated Lagrangian formulation is employed to derive the equilibrium equations, while the contact analysis and implicit time integration for dynamics is maintained from the original DDA. After each time step, the block configuration is updated by adding the new degrees of freedom to the previous coordinates of the block vertices. Results from numerical examples confirm the effectiveness of the proposed approach to prevent false volume expansion, ensure correctness of contact analysis, and provide realistic stress results when simulating large rotations.     

掘进作业中的机械化支护系统的可靠性研究

对平衡式隧道掘进机的机械化支护系统进行可靠性、可维护性分析.分析结果表明,机械化支护系统的三个子系统在超过89％的时间内都是可用的.为了提高系统的可靠性,需要对各个子系统进行预防性维护.根据得到的结果,子系统臂举、支腿和转台的80％可靠性级别的基于可靠性的预防性维修时间间隔分别为180d、120d和360d.     

Glass-ceramic phosphors for solid state lighting: A review

Solid state lighting, including phosphor converted light-emitting diodes (LEDs) and laser diodes (LDs), have released high demand to develop thermally stable phosphors. For this purpose, inorganic glass-ceramics (GCs) embedded with phosphor particles can act as competitive candidates. They are superior to traditional phosphors or resin/silica composites through successfully overcoming thermal aging and color temperature drifting problems and simultaneously maintaining high luminescent efficiencies. Inorganic GC phosphors can be classified into devitrified glass-ceramics, PiG (Phosphor-in-Glass) and sintered glass-ceramics. This review summarized the recent progress on LED/LD GC phosphors from the aspects of design principles, synthesis methods, microstructure-property relationships and their application studies. In addition, some challenging issues (e.g., crystallization behavior of luminous phase in glass, corrosion behavior of phosphor by glass matrix) are also discussed in detail. Significant issues of glass-ceramics packed LED/LD, such as luminescence efficiency, chromaticity, correlated color temperature and color gamut, are sorted out as well. Potential research directions are further suggested for not only developing new glass-ceramic phosphors but feeding upon various practical application.     

可控式citZ基因纳米盒的设计与研究

DNA分子具有自我识别的特殊能力，DNA折纸术就是利用这一特性进行核酸纳米材料精准设计和组装的一种新技术。研究者可以利用与DNA脚手架链互补的订书钉链，将长链核酸折叠成与预设模型一致的纳米结构。DNA折纸术最早是2006年由Rothemund提出，一直以来，人们利用M13mp18单链线性DNA进行各种纳米图形的自组装。为了寻找更多的核酸材料进行DNA折纸研究，本文以枯草芽孢杆菌（Bacillus. subtilis 168）citZ基因序列为研究对象，采用改进的DAEDALUS软件，引入“锁钥”结构设计，利用“从下向上”的方法使DNA分子进行自组装，设计出三维体积为50.71nm×50.71nm×50.71nm的citZ基因纳米盒，只有遇到可识别的基因和匹配的“钥匙”时，才可能打开盖子，释放盒中的内容物。这种核酸纳米材料还可以通过调节DNA序列长度调节盒子的内部空间，有望成为一种新型的靶向药物运送载体。     

Air change rates in urban Chinese bedrooms

The ventilation modalities in most Chinese residences are infiltration and opening windows. We measured infiltration rates and air change rates at night, with no attempt to change occupants' behaviors, of urban residences in five climate zones of China during four seasons. Using the CO₂ decay method, we found the median infiltration rate for 294 residences to be 0.34 h^?1. Using occupant‐generated CO₂ as tracer gas, we determined air change rates over the course of 1 year in 46 bedrooms at night from mass balance considerations. In 54% of the measurements, windows were closed, so ventilation was only by infiltration. Windows were mainly closed when the outdoor temperature was below 15°C and above 26°C. The median infiltration rates did not differ appreciably among seasons and climate zones and were always less than 0.45 h^?1.     

Multifunction properties of SiOC reinforced with carbon fiber and in-situ SiC nanowires

Herein, the SiC nanowires were successfully fabricated via chemical vapor infiltration (CVI) into carbon fiber felts (CFs) and then the SiOC/SiCnws/CFs composites were synthesized by precursor infiltration and pyrolysis (PIP) processes. Results indicated that the lightweight composites possessed enhanced mechanical performance, low thermal conductivity, and excellent electromagnetic wave absorption properties. Detailedly, the compressive strength reached to 22.0 MPa and 9.6 MPa after two PIP processes cycles in z and x/y directions, respectively. Meanwhile, the composites exhibited tailored electromagnetic wave absorption performance with the effective absorption bandwidth of 3.06 GHz, and the minimum reflection loss (RL_min) was -48.2 dB with a thickness of 3.6 mm. The present work has a guidance to prepare and design multifunction properties for application in harsh environment.     

A MoS2 and Graphene Alternately Stacking van der Waals Heterostructure for Li+/Mg2+ Co-Intercalation

Owing to the low-cost, dendrite-free formation, and high volumetric capacity, rechargeable Li⁺/Mg²⁺ hybrid-ion batteries (LMIBs) have attracted great attention and are regarded as promising energy storage devices. However, due to the strong Coulombic interaction of Mg²⁺ with host materials, the traditional “Daniell Type” LMIBs with only Li⁺ intercalation usually cannot ensure a satisfactory energy density. Herein, graphene monolayers are arranged intercalating into MoS₂ interlamination to construct van der Waals heterostructures (MoS₂/G VH). This operation transforms the construction of ion channels from pristine interlamination of two MoS₂ monolayers to the interlamination of MoS₂ monolayer with graphene monolayer, thereby greatly reducing ion diffusion energy barriers. Compared with pristine MoS₂, the MoS₂/G VH can obviously reduce the migration energy barriers of Li⁺ (from 0.67 to 0.09 eV) and Mg²⁺ (from 1.01 to 0.21 eV). Moreover, it is also demonstrated that MoS₂/G VHs realize Li⁺/Mg²⁺ co-intercalation even at a rate current of 1000 mA g⁻¹. As expected, the MoS₂/G VH exhibits superior electrochemical performance with a reversible capacity of 145.8 mAh g⁻¹ at 1000 mA g⁻¹ after 2200 cycles, suggesting the feasibility of potential applications for high-performance energy storage devices.     

连续热镀锌钢板表面露铁原因分析及改进措施

镀锌钢板表面出现连续的氧化现象,镀锌后锌层出现局部脱落,严重影响产品质量与机组生产,对炉区工艺设备排查调整,发现炉区5号高温计轻微泄漏及炉鼻子露点控制不合理,导致炉区露点异常,带钢表面出现氧化,通过修正炉区关键工艺设备点检周期,规范炉鼻子露点管理等措施,彻底解决炉区氧化问题,以及带钢表面局部脱锌问题.