Cure and properties of thermosetting systems

A generalised time-temperature-transformation cure diagram for thermosetting systems is discussed from the point of view of understanding relationships between cure, properties, and thermal degradation.     

一类时滞神经网络系统的局部稳定性与分枝

给出一类时滞神经网络系统的零解的局部稳定判定准则，并给出该系统出现Ｈｏｐｆ分枝的参数条件     

Adaptive Stabilization for a Class of Dynamical Systems with Nonlinear Delayed State Perturbations

The time delays and uncertainties are always encountered in varies of engineering systems, and are the major sources of instability. It is important to investigate the stability and stabilization of those systems. A great deal of attention has been devoted in recent years to the stability analysis and design of controller for the linear uncertainty systems with time-delays[1-7] . For the systems with pseudolinear delay state perturbations, the effective controller also has been designed[8]. It…     

延迟焦化装置掺炼FCC油浆的工业实践

中国石油化工股份有限公司洛阳分公司延迟焦化装置掺炼FCC油浆的比例稳定维持在10%以上,最高达到13.6%。掺炼FCC油浆后,延迟焦化装置的操作苛刻度降低,经济效益可观,每月可创效864万元;但石油焦和蜡油产品质量变差,石油焦挥发分质量分数下降1.25百分点,灰分质量分数上升0.15百分点,蜡油残炭质量分数上升1.19百分点,密度上升67 kg/m~3,装置燃料气、3.5 MPa蒸汽、电的单耗均上升;加热炉炉管和炉出口转油线结焦加剧,炉出口压力上升速率较掺炼油浆前增大0.015 MPa/月;出现了加热炉进料泵出口弯头、跨线阀、进料调节阀阀芯严重磨蚀等问题,装置安全运行风险急剧上升。针对存在问题提出了开展预知性维修、控制油浆固含量、进行设备材质升级、缩短检修周期、优化工艺流程等应对措施和建议。     

Processing of Liaohe Highly Sour Crude

In order to solve the problems related with processing low-quality Liaohe highly sour crude, the Liaohe Petrochemical Company has explored the possibility in optimizing the processing of highly sour crude by adopting different process schemes depending upon the properties of the highly sour crude. The Liaohe naphthenic-base crude oil with low freezing point is earmarked for manufacture of naphthenic lube oils and heavy traffic paving asphalt, while the extra-heavy Liaohe crude with high acid number is routed directly to delayed coking unit coupled with corresponding corrosion preventing measures, resulting in tackling the problem of equipment corrosion arising from refining of Liaohe highly sour crude to obtain light distillates from Liaohe heavy crude through a short process scheme.     

DAWL: A Delayed-ACK Scheme for MAC-Level Performance Enhancement of Wireless LANs

The IEEE 802.11 MAC protocol provides a reliable link layer using Stop & Wait ARQ. The cost for high reliability is the overhead due to acknowledgement packets in the direction opposite to the actual data flow. In this paper, the design of a new protocol as an enhancement of IEEE 802.11 is proposed, with the aim of reducing supplementary traffic overhead and increasing the bandwidth available for actual data transmission. The performance of the proposed protocol is evaluated through comparison with IEEE 802.11 as well as with a SSCOP-based protocol. Results underline significant advantages of the proposed protocol against existing ones, thus confirming the value and potentiality of the approach.Dzmitry Kliazovich received his Masters degree in telecommunication science from Belarusian State University of Informatics and Radioelectronics in 2002. He is currently working towards the Ph.D. degree in University of Trento, Italy. His main research interest lies in wireless networking field with a focus on performance optimization and cross-layer design.Fabrizio Granelli was born in Genoa in 1972. He received the “Laurea” (M.Sc.) degree in Electronic Engineering from the University of Genoa, Italy, in 1997, with a thesis on video coding, awarded with the TELECOM Italy prize, and the Ph.D. degree in Electronic Engineering and Computer Science from the same university in 2001. Since 2000 he is carrying on his teaching activity as Assistant Professor at the Dept. of Information and Communication Technologies (DIT) of the University of Trento (Italy) within the B.Sc. and M.Sc. Degrees in Telecommunications Engineering.The research interests of Dr. Granelli are mainly focused on networking, with particular attention to network modeling and performance evaluation, wireless networks, access control, and next-generation telecommunication networks.He is author of more than 30 refereed papers, published in several international journals and conferences.Dr. Granelli is member of the IEEE Committee on “Communication Systems Integration and Modeling” (CSIM) and of the Technical Programme Committee of the “QoS and Performance Evaluation Symposium” of the International Conference on Communications (ICC 2003 and ICC 2004).     

Tuning the optical absorption of potential blue emitters

The quest for more efficient blue emitters to be applied in organic light-emitting diodes is one of the challenging tasks of contemporary nanotechnologies. An approach to enhance substantially the intrinsic efficiency of luminescent organic molecules is the so-called thermally activated delayed fluorescence. A prerequisite for its occurrence is a vanishing energy separation between the first singlet and triplet excited states. A series of donor–acceptor molecules is investigated theoretically within this study in order to validate a molecular model for design of efficient organic blue emitters with closely spaced singlet and triplet excited states. The model is based on meta-linkage of the donor and acceptor residues to a spacer ensuring frontier molecular orbitals partitioning. The optimal geometries of the molecules are obtained with density functional theory (B3LYP/6-31G^*) and the singlet and triplet absorption spectra are simulated within the time-dependent density functional framework. The excited singlet-triplet energy gap is estimated and correlated to structural and energetic characteristics of the donors and acceptors. Several requirements for achieving high-energy triplet states at the molecular level in such donor–acceptor systems are outlined, the main being disjoint character of the molecular orbitals on the spacer and sufficient energy separation of the two topmost occupied orbitals. It is shown that by variation of the acceptor moiety the optical absorption transitions of the compounds can be fine-tuned in a systematic fashion. Molecules with degenerate singlet and triplet first excited states are proposed, combining bisdimethylaminotriphenylamine or phenoxazine as donors with diphenyloxadiazole or diphenyl-2,2′-bipyridine as acceptors. Bipolar molecules derived from this model could be used as prospective building blocks for efficient emissive materials in blue organic light-emitting diodes.     

苯乙烯焦油综合利用的研究进展

苯乙烯焦油为苯乙烯生产过程中产生的副产品,其主要成分是苯乙烯聚合物以及组成复杂的衍生物、低聚物等,一般作为燃料燃烧或废物出厂.随着环保管控的升级,苯乙烯焦油的加工利用难度也随之增大.近年来,为解决苯乙烯焦油的有效利用问题,以提高其利用价值,对其进行了研究,主要包括炼油装置掺炼,回收有效组分,制备磺酸盐,用于石油开采等方...     

Are disulphide bonds formed during acid gelation of preheated milk?

The role of thiol/disulphide exchanges during acid gelation of preheated milk was studied with milk samples with or without N‐ethylmaleimide (NEM), a thiol‐blocking agent, and acidified to pH 4 by the addition of glucono‐delta‐lactone at 20 °C. Active or total thiol groups, particle size with light scattering measurements in a dissociating solvent or by SDS‐agarose electrophoresis were determined on acidified milk samples. Diffusing wave spectroscopy and rheology in low strain were applied during acidification of sample, while rheology in large strain was applied on final acid gels. The only effect of the presence of NEM was a reduced firmness of acid gels as measured at large strain and a reduced tendency to form large aggregates at pH<5.5. In conclusions, thiol/disulphide exchanges during acidification of milk played only a minor role in the building of acid gel networks from heated milk.