Optimal load rating-based inspection planning of corroded steel girders using Markov decision process

Steel girder bridges are vulnerable to corrosion. To maintain their safety above a predefined target level, the load rating can be computed from the inspection results and guide the following maintenance actions. Optimizing inspection and maintenance based on load ratings has substantial practical and economic relevance. Load rating-based strategies can be categorized based on whether the inspection interval and replacement criteria are fixed or flexible. Existing studies focus on fixed inspection intervals throughout the service life. In general, their results are not optimal for inspection planning. To reduce life-cycle cost, aged steel girders may be inspected and repaired in an adaptive manner. To this end, a method based on Markov decision process (MDP) is proposed to compare the life-cycle cost of four load rating-based policies (i.e. uniform or adaptive non-uniform inspection interval, and fixed or adaptive replacement threshold). Load rating-based inspection planning is formulated as MDP and the optimal plans are obtained using dynamic programming. The conventional approach to discretize states cannot accurately approximate the non-stationary deterioration process, while state augmentation is successful in doing this but will increase computational cost. A comparison of two approaches is made to investigate their effects on life-cycle cost. A bridge girder under corrosion attack is used as an illustrative example. The results show that the load rating-based plan with an adaptive non-uniform inspection interval and fixed replacement threshold obtained using the state augmentation technique can be near-optimal.     

基于改进灰狼优化算法的服务功能链映射算法

随着工业互联网、车联网、元宇宙等新型互联网应用的兴起，网络的低时延、可靠性、安全性、确定性等方面的需求正面临严峻挑战。采用网络功能虚拟化技术在虚拟网络部署过程中，存在服务功能链映射效率低与部署资源开销大等问题，联合考虑节点激活成本、实例化开销，以最小化平均部署网络成本为优化目标建立了整数线性规划模型，提出基于改进灰狼优化算法的服务功能链映射（improved grey wolf optimization based service function chain mapping，IMGWO-SFCM）算法。该算法在标准灰狼优化算法基础上添加了基于无环K最短路径（K shortest path，KSP）问题算法的映射方案搜索、映射方案编码以及基于反向学习与非线性收敛改进三大策略，较好地平衡了其全局搜索及局部搜索能力，实现服务功能链映射方案的快速确定。仿真结果显示，该算法在保证更高的服务功能链请求接受率下，相较于对比算法降低了11.86%的平均部署网络成本。     

不同种源地香叶树籽的油脂含量及脂肪酸组成分析

为探明不同种源地香叶树作为油料树种的开发价值，采集了全国6省20县市的香叶树果实，对香叶树全果、果肉及籽的油脂含量及脂肪酸组成进行了分析，并采用ward法对不同种源地香叶树籽油脂肪酸进行了聚类分析。结果表明：香叶树全果、果肉以及籽的平均油脂含量分别为43.31%、42.38%及46.12%；全果油脂肪酸组成以月桂酸、油酸和癸酸为主；果肉油以油酸和棕榈酸为主；而籽油则以月桂酸和癸酸为主，月桂酸含量为53.20%~70.30%，月桂酸和癸酸总含量达76.40%~90.10%；聚类分析将不同种源地香叶树分为3大类，云南省、贵州省及广西省的香叶树属低月桂酸类型，福建省、江西省及湖南省的香叶树属中高月桂酸型。香叶树可作为生产中碳链脂肪酸的新晋树种，福建省的香叶树籽油脂含量高，且籽油中月桂酸含量高，作为中碳链脂肪酸的原料地具有明显的开发优势。     

Intensity enhancement of photoluminescent polyesters by photocrosslinking

A series of polyesters with alkylated triazole heterocyclic rings at the branches were designed and synthesized via the polycondensation reaction. The synthesized polyesters were examined with various spectroscopic methods such as Fourier transform IR, ¹H NMR and ¹³C NMR. The alkyl chain length at the branch was found to affect the thermal stability of the polyesters, which decreased with longer alkyl chain. These polyesters possessed an aggregation‐induced emission enhancement characteristic evidenced by the transformation of the clear solutions in tetrahydrofuran with weak greenish blue emission to cloudy solutions with enhanced blue emission when water was added to promote aggregation. Furthermore, enhancement in the photoluminescence intensity was observed when the polyesters underwent photocrosslinking upon UV irradiation and appeared as self‐assembled aggregates. The formation of aggregates in the water ? tetrahydrofuran solutions and after photocrosslinking was confirmed via TEM analysis. The SEM images showed that the photocrosslinked polyesters were highly porous which may enhance the π ? π stacking interaction that improved the photoluminescence intensity. © 2015 Society of Chemical Industry     

Fast retrieval of hidden data using enhanced hidden Markov model in video steganography

In the digital world, secure data communication has an important role in mass media and Internet technology. With the increase in modern malicious technologies, confidential data are exposed at a greater risk during data communication. For secured communication, recent technologies and the Internet have introduced steganography, a new way to hide data. Steganography is the growing practice of concealing data in multimedia files for secure data transfer. Nowadays, videos are more commonly chosen as cover media than other multimedia files because of the moving sequence of images and audio files. Despite its popularity, video steganography faces a significant challenge, which is a lack of a fast retrieval system of the hidden data. This study proposes a novel video steganography technique in which an enhanced hidden Markov model (EHMM) is employed to improve the speed of retrieving hidden data. EHMM mathematical formulations are used to enhance the speed of embedding and extracting secret data. The data embedding and retrieving operations were performed using the conditional states and the state transition dynamics between the video frames. The proposed EHMM is extensively evaluated using three benchmark functions, and experimental evaluations are conducted to test the speed of data retrieval using differently sized cover-videos. Results indicate that the proposed EHMM yields better results by reducing the data hiding time by 3–50%, improving the data retrieval rate by 22–77% with a minimum computational cost of 20–91%, and improving the security by 4–77% compared with state-of-the-art methods.     

A data propagation model for wireless gossiping

Wireless sensor networks require communication protocols for efficiently propagating data in a distributed fashion. The Trickle algorithm is a popular protocol serving as the basis for many of the current standard communication protocols. In this paper we develop a mathematical model describing how Trickle propagates new data across a network consisting of nodes placed on a line. The model is analyzed and asymptotic results on the hop count and end-to-end delay distributions in terms of the Trickle parameters and network density are given. Additionally, we show that by only a small extension of the Trickle algorithm the expected end-to-end delay can be greatly decreased. Lastly, we demonstrate how one can derive the exact hop count and end-to-end delay distributions for small network sizes.     

浅析有效交互技术基础上的网络远程教学

本文主要简单的介绍了网络远程教学的内容,对有效交互技术的相关内容和特点进行了分析,研究将有效交互技术引入网络远程教学中的重要性,探讨网络远程教学中交互技术应用和设计的原则,以思考在交互技术上实施网络远程教学活动的有效措施,从而保障网络远程教学质量。据此,有利于培养学生对网络远程学习的兴趣,充分发挥交互技术的作用,以提高学生的学习效果,实现网络远程教学效益最大化。     

Gender differences in the meanings associated with food hazards: A means-end chain analysis

It is a common finding that men compared to women are less concerned about food hazards and technologies. While previous literature analyzed determinants such as trust in public actors in order to explain gender differences in food risk perception, a systematic analysis of women’s and men’s cognitions (associations) and emotions (feelings) is lacking. This study focuses on the very first associations and the deeper motives and values that women and men link to three potential food hazards: mycotoxins, pesticides and irradiation. Means-end chain theory was applied and in-depth laddering interviews were conducted with 34 women and 35 men in Munich, Germany. The results reveal that food hazards threaten self-centered and socio-altruistic values of men and women alike and that ‘care for others’ is not only a motive for women.     

Synthesis of thermoresponsive block and graft copolymers via the combination of living cationic polymerization and RAFT polymerization using a vinyl ether-type RAFT agent

A novel vinyl ether-type RAFT agent, benzyl 2-(vinyloxy)ethyl carbonotrithioate (BVCT) was synthesized for various block copolymers via the combination of living cationic polymerization of vinyl ethers and reversible addition−fragmentation chain transfer (RAFT) polymerization. The novel BVCT–trifluoroacetic acid adduct play an important role to produce well-defined block copolymers, which is both as a cationogen under EtAlCl₂ initiation system in the presence of ethyl acetate for living cationic polymerization and a RAFT agent for blocks by RAFT polymerization. The resulting polymer, poly(vinyl ether)s, by living cationic polymerization had a high number average α-end functionality (≥0.9) as determined by both ¹H NMR and MALDI-TOF-MS spectrometry. In addition, this poly(vinyl ether)s worked well as a macromolecular chain transfer agent for RAFT polymerization. The RAFT polymerization of radically polymerizable monomers was conducted in toluene using 2,2′-azobis(isobutyronitrile) at 70 °C. For example, a double thermoresponsive block copolymer (MOVE₆₁-b-NIPAM₁₅₀) consisting of 2-methoxyethyl vinyl ether (MOVE) and N-isopropylacrylamide (NIPAM) was prepared via the combination of living cationic polymerization and RAFT polymerization. The block copolymer reversibly formed and deformed micellar assemblies above the phase separation temperature (T_ps) of poly(NIPAM) block in water. This BVCT is not only functioned as an initiator, but also acted as a monomer. When BVCT was copolymerized with MOVE by living cationic polymerization, followed by graft copolymerization with NIPAM via RAFT polymerization, well-defined graft copolymers (MOVE_n-co-BVCT_m)-g-NIPAM_x (n = 62–73, m = 1–9, x = 19–214) were successfully obtained. However, no micelle formed in water above T_ps of poly(NIPAM) graft chain unlike the case of block copolymers.     

Synthesis of low molecular weight polyethylenes and polyethylene mimics with controlled chain structures

The controlled synthesis of narrowly distributed low molecular weight polymers with functionalization possibilities is of great industrial interests. Although living polymerization allows for control over polymer architecture, the production of low molecular weight polymers with low polydispersities via living polymerization systems is challenged by the use of large amounts of catalysts and broadening in molecular weight distribution. This review addresses the synthesis of narrowly distributed, functional, low molecular weight polyethylene and polyethylene mimics. The review is structured for quick identification of relevant systems for the production of specific polymer architectures with specific cost, efficiency, and safety concerns.