纳米粘土/炭黑/天然橡胶复合材料动态性能的研究

以纳米粘土部分等量替代炭黑填充天然橡胶(NR),制备纳米粘土/炭黑/NR复合材料,研究纳米粘土用量对复合材料动态性能的影响。结果表明:当纳米粘土用量较小时,纳米粘土/炭黑/NR复合材料中填料分散性较好;与炭黑/NR复合材料相比,纳米粘土/炭黑/NR复合材料的滞后损失、动刚度和动静刚度比降低,当纳米粘土用量为2份时,复合材料的动态压缩生热和动静刚度比最低。     

抗硫化返原剂BCI对NR胶料性能的影响

将自制的4,4′-N,N′-二苯甲烷双柠康酰亚胺(BCI)用作抗硫化返原剂,研究其对NR胶料性能的影响,并与抗硫化返原剂PK900进行对比。结果表明,BCI具有与PK900相近的抗硫化返原性能,与未加抗硫化返原剂的胶料相比,加入BCI的胶料ML和MH减小,t10和t90变化不大;硫化胶的定伸应力和拉伸强度增大,拉断伸长率减小。裂解气相色谱分析表明,BCI在NR硫化返原过程中形成了新的C—C交联键。     

侵蚀条件下天然橡胶桥梁支座胶料拉伸性能的研究

针对天然橡胶(NR)桥梁支座的使用条件,研究在冻融、盐冻、热老化以及强酸腐蚀条件下NR桥梁支座胶料的拉伸性能。结果表明:随着冻融次数的增加,胶料的拉伸应力下降,但降幅不大,抗冻融能力较强;经过60次盐冻循环后,胶料的最大拉伸应力下降4.1%,抗盐冻能力较强;随着热老化时间的延长,胶料的拉伸应力下降幅度较大,在湿热环境中应加强NR桥梁支座的热老化防护;经过强酸腐蚀后,胶料的拉伸应力下降幅度较大,经硝酸、硫酸和亚硝基硫酸分别腐蚀60 d后,胶料的最大拉伸应力分别降低16.2%,17.2%和14.1%。     

碱活化改性高岭土/NR复合材料的结构和性能研究

采用凝聚共沉法制备碱活化改性高岭土／NR复合材料，并对其物理性能和微观结构进行研究。结果表明，高岭土改性时间为3d、改性高岭土与天然胶乳混合温度为45℃、改性高岭土用量为40份时，碱活化改性高岭土／NR复合材料的综合物理性能较好；改性高岭土在NR基体中发生了定向排列，基本上以面-面平行状态均匀分散，大部分高岭土以厚度为25-75nm的层叠形式平行分布在NR基体中；改性高岭土与NR基体间形成过渡层。     

粘土/炭黑/NR纳米复合材料的性能研究

在乳液插层法制备的粘土／NR纳米复合材料中加入炭黑，制得粘土／炭黑／NR纳米复合材料，并对其微观结构和性能进行研究。结果表明，炭黑的加入并没有影响粘土在NR基体中的分散状态，粘士炭黑和在NR基体中均达到纳米级分散；炭黑的加入削弱了粘土所形成填料网络的强度，从而改善了复合材料的加工性能；与粘土／NR纳米复合材料相比，粘土／炭黑／NR纳米复合材料的综合物理性能较好。     

我国轮胎产业的发展及其对橡胶和骨架材料的需求

分析我国轮胎工业发展现状和前景以及对橡胶和骨架材料的需求,今后几年我国轮胎产业仍将保持快速发展势头,预计2010年全国轮胎总需求量将达到41330万条,年均增长9.3%,其中子午线轮胎32230万条,子午化率为78%,年均增长率为14.6%;2010年我国轮胎的耗胶量预计为420万t.年均增长率为7.9%,其中NR为247万t,SR为173万t,SR比例将提高到41%;由于载重子午线轮胎和工程机械子午线轮胎的发展,钢丝帘线需求量仍将继续扩大,2010年将达到95万t,年均增长率为15%,使用比例将提高到骨架材料的75%.     

Physical layer enhancements in 5G-NR for direct access via satellite systems

Among the several features and capabilities introduced by every new 3GPP release on 5G cellular systems, the latest Release 17 will be remembered as the first that specifies a set of enhancements and adaptations to support mobile broadband services via satellite direct access. Specifically focused on the necessary physical layer mechanism and procedure modifications, this paper will present in detail the 3GPP work about the inclusion of satellite systems in 5G networks.     

An Enhanced Group Key-Based Security Protocol to Protect 5G SON Against FBS

Network operators are attempting many innovations and changes in 5G using self-organizing networks (SON). The SON operates on the measurement reports (MR), which are obtained from user equipment (UE) and secured against malware and userspace programs. However, the synchronization signal block that the UE relies on to measure the wireless environment configured by a base station is not authenticated. As a result, the UE will likely gauge the wrong wireless environment configured by a false base station (FBS) and transmit the corresponding MR to the serving base station, which poisons the data used for 5G SONs. Therefore, the serving base stations must verify the authenticity of the MR. The 3GPP has advocated numerous solutions for this issue, including the use of public key certificates, identity-based keys, and group keys. Although the solution leveraging group keys have better efficiency and practicality than the other two, they are vulnerable to security threats caused by key leaks via insiders or malicious UE. In this paper, we analyze these security issues and propose an improved group key protocol that uses a new network function, called a broadcast message authentication network function (BMANF), which validates broadcasted messages on behalf of the UE. The protocol operates in two phases: initial and verification. During the initial phase, the 5G core network distributes a shared secret key to the BMANF and UE, allowing the latter to request an authentication ticket from the former. During the verification phase, the UE requests the BMANF to validate the broadcasted messages received from base stations using the ticket and its corresponding shared key. For evaluation, we formally verified the proposed protocol, which was then compared with alternative methods in terms of computing cost. As a result, the proposed protocol fulfills the security requirements and shows a lower overhead than the alternatives.     

Radio interface protocols and radio resource management procedures for 5G new radio non-terrestrial networks

In Release 17, 3GPP introduced adaptations and enhancements to the 5G new radio (NR) specification to support non-terrestrial networks (NTNs) operation. The main challenges were due to long propagation delays, especially in GEO deployments, and the movement of the satellites in LEO deployments. In this paper, we give an overview of the protocol adaptations to support NTNs. The main user plane protocol adaptations include changes to random access and hybrid automatic repeat request to due long propagation delays. The control plane protocol adaptations include a variety of mobility related enhancements for user equipment.