Cationic polymerization with p-substituted benzyl p-hydroxyphenyl methyl sulfonium salts: Effect of substituents and mechanistic aspects of initiation reaction

Various p-substituted benzyl p-hydroxyphenyl methyl sulfonium salts ( 2 ) were synthesized and their initiator activities were evaluated in bulk polymerization of glycidyl phenyl ether (PGE). The order of the activity was found to be 2b (X = CH₃) > 2a (X = H) ≈ 2c (X = Cl) > 2d (X = NO₂), indicating that the introduction of an electron-donating group enhanced the activity. In Hammett's plots, the logarithm of the ratio of the polymerization rates (log k_x/k_H) was correlated with σ⁺_ρ better than with σ_p and a negative ρ⁺ value (-1.18) was obtained. Reaction of 2a with benzyl mercaptan mainly gave dibenzyl sulfide and p-hydroxyphenyl methyl sulfide. The obtained results seemed to demonstrate that the OH group of the aryl group yielded no proton as initiator for the polymerization, whereas the benzyl group caused the polymerization, which was initiated by the corresponding benzyl cation formed by C? S bond cleavage. © 1993 John Wiley & Sons, Inc.     

Fast control latency uncertainty elimination for the BESIII ETOF upgrade

A new fanning topology is proposed to precisely fan out fast control signals in the Beijing Spectrometer(BESIII) end-cap time-of-flight(ETOF) electronics. However, uncertainty in transfer latency is introduced by the new fanning channel, which will degrade the precision of fast control. In this paper, latency uncertainty elimination for the BESIII ETOF upgrade is introduced. The latency uncertainty is determined by a Time-Digital-Converter(TDC) embedded in a Field-Programmable Gate Array(FPGA) and is eliminated by re-capturing at synchronous and determinate time. Compared with the existing method of Barrel-cap TOF(BTOF), it has advantages of flexible structure, easy calibration and good adaptability. Field tests on the BESIII ETOF system show that this method effectively eliminates transfer latency uncertainty.     

Design of a Two-layer Scalable Wavelength Routing Optical Interconnection Network

In this paper, a two-layer scalable wavelength routing optical interconnection network is presented. The top layer of the network is a multi-wavelength bi-directional optical bus which has high-bandwidth and low-latency; the sub-layer of the network is single-wavelength synchronous pipelined ring which has low communication latency and high-scalability. The way to implement the optical system of the network is put forward, and the synchronous pipelined optical interconnect ring is designed and implemented.     

无线传感器网络中基于最小延时的数据汇集树构建与传输调度算法

无线传感器网络的数据通信模式问题是目前的研究热点,针对现有的无线传感器网络数据汇集算法延时较大这一不足,对最小延时数据汇集树和传输调度问题进行了研究。提出一种基于度约束的汇集树构建算法(DCAT)。该算法按照 BFS 方式遍历图,当遍历到每个节点时,通过确定哪些节点与汇点更近来确定潜在母节点集合。然后,选择图中度数最小的潜在母节点作为当前被遍历节点的母节点。此外,为了在给定的汇集树上进行高效地数据汇集,还提出两种新的基于贪婪的TDMA传输调度算法：WIRES-G 和 DCAT-Greedy。利用随机生成的不同规模的传感器网络,参照当前最新算法,对文中方法的性能进行了全面评估。结果表明,与当前最优算法相比,文中调度算法与文中汇集树构建算法结合起来,可显著降低数据汇集的延时。     

Profit-based latency problems on the line

We consider a latency problem with a profit p_i for each client. When serving a client, a revenue of p_i−t is collected. The goal is to find routes for the servers such that total collected revenue is maximized. We study the complexity of different variants of this problem on the line.     

URLLC occasional large time delay prediction based on unbalanced regression and LSTM

Occasional large time delay is one of the bottlenecks for 5G applied to the industrial field. Accurate measurement, analysis, and prediction of communication network latency are of great significance. Due to the strong randomness and small number of samples in ultra-reliable and low latency communication (URLLC), the prediction task of occasional large time delay is very challenging. This paper proposes an URLLC occasional large time delay prediction method based on unbalanced regression algorithms and long–short term memory (LSTM). We first decompose the original sequence by using the variational mode decomposition (VMD) to obtain relatively stable component sequences. The parameters of the VMD are automatically optimized by grasshopper optimization algorithm (GOA). In order to improve the prediction effect of URLLC occasional large time delay, we introduce unbalanced regression algorithms. Before the VMD decomposition of data samples, the SMOGN is introduced to balance the number of large-time delay samples and common-time delay samples. Next we calculate the weight of each sample based on the rarity of each sample point and our proposed LDSWeight. Finally, LSTM is used to complete cost-sensitive learning. The experimental results show that the URLLC occasional large time delay prediction method proposed in this paper has better prediction accuracy than other methods.     

Delay-Sensitive NOMA-HARQ for Short Packet Communications

This paper investigates the two-user uplink non-orthogonal multiple access (NOMA) paired with the hybrid automatic repeat request (HARQ) in the finite blocklength regime, where the target latency of each user is the priority. To limit the packet delivery delay and avoid packet queuing of the users, we propose a novel NOMA-HARQ approach where the retransmission of each packet is served non-orthogonally with the new packet in the same time slot. We use a Markov model (MM) to analyze the dynamics of the uplink NOMA-HARQ with one retransmission and characterize the packet error rate (PER), throughput, and latency performance of each user. We also present numerical optimizations to find the optimal power ratios of each user. Numerical results show that the proposed scheme significantly outperforms the standard NOMA-HARQ in terms of packet delivery delay at the target PER.