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Sustainable low melting temperature bicomponent polyester fibers that can be circularly recycled were developed. The potentially biobased poly(hexamethylene terephthalate) (PHT), acting as the low ...

The cable-stayed fastening-hanging cantilever construction method has been widely used in the construction of arch bridges. Hanging cables’ parametric vibration frequently appears during the cantilever construction stage of arch rings. However, there is a lack of research on hanging cables’ parametric vibration as well as its control strategies for inerter dampers. Although Runge-Kutta method can achieve the transient response of cables’ parametric vibration under arbitrarily support excitation, it might not achieve the large-amplitude solution due to inappropriate initial conditions. Therefore, parametric vibration equation of hanging cable with parallel inerter damper was established and solved both by Runge-Kutta method and method of multiple scales(MMS). The steady-state solution of hanging cables calculated by Runge-Kutta method and its dependence on initial conditions were discussed and analyzed. Numerical stability of Runge-Kutta solution was also investigated by analyzing the phase portraits of multiple-scale solution. Besides, the influence of inerter damper on Runge-Kutta solutions’ numerical stability and initial condition dependence was discussed and explained. Finally, a general method to determine initial conditions of Runge-Kutta method was proposed to achieve large-amplitude solution of hanging cables’ parametric vibration under arbitrary support excitation. The results indicate that different initial conditions cause Runge-Kutta’s transient amplitude to develop along different phase trajectories, and finally to converge to different steady-state solutions. The inerter damper changes the critical phase trajectory of cable-inerter system, which shifts the region of reasonable initial conditions. Runge-Kutta steady-state solutions with inerter damper, solved by the initial conditions for no inerter damper case, may be the small-amplitude solutions, which may lead to overestimation of the control effect of inerter dampers. This study provides a general method to determine initial conditions of Runge-Kutta method for cables’ parametric vibration, which provides a reference for future parametric vibration studies.

To account for the influence of winglet’s arrangement length and installing position along the longitudinal direction of bridge deck, as well as actuators quantities on flutter control effect, a three-dimensional model of deck-winglet system was been derived in state space domain, and a model reduction method was also discussed to enhance control efficiency. Then, a suspension bridge with a main span of 3[Formula: see text]000[Formula: see text]m was used to investigate the control effect of active winglets, and to explore the influence of winglet length and actuator quantity on flutter control effect. Finally, the flutter and buffeting performance of winglet itself was investigated. The simulation results shows that the modes involved in flutter analysis should be determined according to mode-energy participation ratio. When installing a pair of winglets whose width is 10% of bridge deck, the critical wind speed of bridge deck may be twice of a non-controlled condition. In addition, the critical wind speed increases by increasing the length of winglets and actuator quantity. However, the critical wind speed may remain constant once the winglet length and actuator quantity exceed a critical value. By ensuring the critical wind speed of winglet itself is higher than bridge deck, winglet’s width should be less than 10% of bridge deck’s width, and the independent length winglet is proposed to be shorter than 15% of the length of center span of bridge deck.

A rigid diol with a cyclic acetal structure was synthesized by facile acetalation of fructose-based 5-hydroxymethyl furfural (HMF) and partly bio-based di-trimethylolpropane (di-TMP). This diol (Monomer T) was copolymerized with potentially bio-based flexible polytetrahydrofuran and diisocyanates to prepare thermoplastic poly(cycloacetal-urethane)s. A modified one-step solution polymerization protocol resulted in relatively high molecular weights (Mn ∼ 41.5–98.9 kDa). All the obtained poly(cycloacetal-urethane)s were amorphous with tuneable glass transition temperatures up to 104 °C. Thermogravimetric analysis indicated that these polymers were thermally stable up to 253 °C and had a relatively high pyrolysis char residue, which may indicate potential inherent flame resistance. Melt rheology measurements were performed to determine a suitable processing window between 165–186 °C, after which the polymer was successfully melt-spun into ∼150 meters of homogeneous fibres at 185 °C. The resulting fibres could be readily hydrolysed under acidic conditions, resulting in partial recovery of the original chemical building blocks.

This paper reviews various active control measures used for controlling the wind-induced vibration, which is a problem of great concern for long-span suspension bridges. Firstly, a brief discussion of passive control measures and their limitations is presented. Then, the development of active aerodynamic control and active mechanical control is comprehensively reviewed to present the characteristics and limitations of numerous control devices with emphasis on the control surfaces adopted for active aerodynamic control. Particularly, the existing challenges and suggestions for future studies are proposed for various countermeasures, especially for the control surfaces used in active control. It is expected that the information provided in this article will facilitate further research in the area of vibration control for long-span suspension bridges under various wind conditions.

The present paper combined the natural environment excitation technology (NExT) with the eigen system realization algorithm (ERA) to identify the modal parameters of a suspension bridge. Firstly, the critical parameters in NExt–ERA, such as record length, window length, and ranks of the Hankel matrix, and their influence on identification accuracy have been discussed. Subsequently, based on the acceleration series obtained from the Xihoumen Bridge Health Monitoring System, 3015 sets of modal frequencies and modal damping ratios of the Xihoumen Bridge were identified under 7 sets of wind speeds by the NExt–ERA. Finally, the probability distribution and confidence interval of the structural modal damping ratios were analyzed. Besides, the dependence of identified frequencies damping ratios on wind speed was also discussed. The results show that at the same wind speed, the mean value, and variance of the torsional and lateral mode damping ratios are larger than those of the vertical mode, but this difference gradually decreases with the increment of wind speed. The modal damping ratios along three directions under different wind speeds all follow the generalized extreme value distribution, but wind speed affects the tailing properties of probability distribution of the vertical and torsional mode damping ratios. The estimated damping ratios could provide references for structural design and vibration control of similar long-span bridges.

In order to study the parametric vibration of stayed cables in a long cantilever bridge for a sightseeing platform, nonlinear parametric vibration equations of the stayed cables excited by the vibration of bridge deck and tower are derived. Then, a second-order differential equation is transformed into a first-order ordinary differential equation, which is solved by using the Runge–Kutta method. A finite element model of cables was also built to verify the solution of the Runge–Kutta method. Then, the inherent dynamic characteristics of the full structure and all the cables with different lengths were analyzed to discuss the potential risk of parametric vibration. The longest and shortest cables were taken as examples to explore their nonlinear vibration performance. The effects of damping ratio, excitation position, and amplitude on cables’ nonlinear vibration performance were investigated. The results show that it will be more efficient and convenient to use the Runge–Kutta method to calculate cables’ nonlinear vibration amplitude without loss of accuracy. In addition, short cables have more resonance zones compared to long cables. Especially, with the cable length shortening, the dominant frequencies of the dynamic response and its amplitude increase significantly, and the number of resonance zones also increases. However, excessive excitation amplitude will also cause multiple resonance zones in the cable. The parametric analysis results show that it is effective and efficient to mitigate the nonlinear vibration by adjusting the frequency relationship between the bridge and the cables, rather than by increasing the damping ratio.

Magnetic Mg-Al-O@Fe3O4 micro particles were synthesized by coating nanosized Mg-Al double oxides onto Fe3O4 micro particles. The formed hierarchical structure gave Mg-Al-O@Fe3O4 micro particles a high active surface area, which enabled these micro particles to work efficiently as a catalyst in the glycolysis of poly(ethylene terephthalate) (PET). The bis(hydroxyethyl) terephthalate (BHET) yield reached above 80 mol% in the presence of 0.5 wt% of Mg-Al-O@Fe3O4 micro catalyst in the reaction system within 90 min at 240 °C. After the reaction, Mg-Al-O@Fe3O4 micro catalyst was easily retrieved by a magnetic decantation and can be repetitively used for two times with a high catalytic efficiency. After that, the deactivated Mg-Al-O@Fe3O4 micro catalyst can be regenerated by heat treatment. The regenerated Mg-Al-O@Fe3O4 micro catalyst displays a comparable catalytic performance as that of the virgin catalyst. In addition, the Mg-Al double oxides and Fe3O4 micro particles are low-cost and environmentally benign. Therefore, the Mg-Al-O@Fe3O4 micro catalyst may contribute to an economically and environmentally improved large-scale circular recycling of PET fiber waste.

This paper investigated the relationship between the morphology of corrosion pits and the stress concentration factor. Several images of corroded wire with different corrosion durations were obtained based on corrosion-accelerated test under the coupling effect of alternating load and salt-spray environment, then the morphology and size of pits were identified by the maximum entropy threshold segmentation method. A finite-element model of high-strength wire with corrosion pits was constructed and analyzed to explore the stress concentration factor close to the corrosion pits. Subsequently, a Bayesian prediction model of the stress concentration effect on wires with corrosion pits was proposed. In conclusion, the morphology of corrosion pits was described as “ellipsoidal”, with its length and width obeying the lognormal distribution and its depth obeying the Weibull distribution. Bayesian analysis indicated that the stress concentration factors around a corrosion pit were affected by the length–width and width-depth ratios of the pit. The stress concentration effect close to corrosion pits with narrow or deep appearance was more dramatic than that of other pits.

A tremendous amount of polyester textile waste is discarded every year, which has caused a serious problem for the environment. In this study, the feasibility of circular recycling of polyester textile waste is investigated through a glycolysis process in the presence of environmentally friendly Mg–Al double oxides pellets as catalyst. Even though the catalytic performance of Mg–Al double oxides pellets is slightly lower than their granules at 240 °C, pellets were used as they benefit from a good recyclability. The pellet catalysts could be cycled three times without losing structural integrity or catalytic activity in the glycolysis of (poly(ethylene terephthalate)(PET)). However, to restore the catalytic activity after three cycles, the catalyst was regenerated through a heat treatment after the glycolysis reaction. After that the catalyst showed a comparable catalytic activity as that of virgin catalyst. In the glycolysis process, the monomer bis(hydroxyethyl) terephthalate (BHET) is generated and recovered. The molar yield of BHET was in the reaction over 80 mol%. From the recovered BHET, regenerated PET (r-PET) with an intrinsic viscosity (IV) of 0.67 was synthesized. The r-PET showed a very good spinnability in the melt spinning test. The quality of the obtained r-PET fibers was comparable to virgin PET fibers.

Polyvinylidene fluoride (PVDF) fibers with a high amount of phase crystal structure were prepared by melt spinning. With this technique, the cold drawing process is critical and efficient when aiming for a high amount of phase. During the cold drawing process, more than 80% of the originally formed phase crystal structure was converted into the phase structure. In addition, the incorporation of 0.01 wt % of amino-modified double wall carbon nanotube (NH2-DWCNT) could further enhance the phase content in the PVDF fibers. FTIR and DSC studies showed that the addition of NH2-DWCNT to PVDF fibers could increase both the total crystallinity and phase fraction in PVDF. The addition of nanoclay was found to be less efficient in this respect

This paper presents a new analysis framework for predicting the internal buffeting forces in bridge components under skew wind. A linear regressive model between the internal buffeting force and deformation under normal wind is derived based on mathematical statistical theory. Applying this regression model under normal wind and the time history of buffeting displacement under skew wind with different yaw angles in wind tunnel tests, internal buffeting forces in bridge components can be obtained directly, without using the complex theory of buffeting analysis under skew wind. A self-anchored suspension bridge with a main span of 260 m and a steel arch bridge with a main span of 450 m are selected as case studies to illustrate the application of this linear regressive framework. The results show that the regressive model between internal buffeting force and displacement may be of high significance and can also be applied in the skew wind case with proper regressands, and the most unfavorable internal buffeting forces often occur under yaw wind.

Melt spinning of nanoclay (NA)/polypropylene (PP) composites into textile fibers is studied. The synthetic NA Perkalite F100 is prone to be exfoliated in PP matrix. With the help of a maleic anhydride-grafted low-molecular-weight PP as compatibilizer (Epolene E43), a highly exfoliated PP/NA composite was successfully prepared. However, the prepared PP/NA composite shows a poor spinnability because of the phase separation between Epolene E43 and PP matrix. The combination of two different groups of compatibilizers, which are Polybond 1001 (acrylic acid-grafted PP) for the dispersion of NA and Epolene G3216 (maleic anhydride-grafted PP-based copolymer) for the exfoliation of NA, can solve this problem. The PP/NA composite prepared by these two compatibilizers can be smoothly spun into fiber at the NA concentration below 1.9 wt%, which is found to be the percolation concentration of formation of NA network structure in PP matrix.

The chemical structure of polymers obtained through enzyme-catalyzed reactions can be controlled by the addition of chemical structure-controlling templates. Examples are reviewed and discussed. Although this concept is applied successfully, it seems to be limited to polymerization reactions which are initiated by certain oxidoreductases (for example peroxidases or laccases). This conclusion is based on the consideration of (i) selected examples of enzymatic in vitropolymerizations and (ii) some of the key features of the biosynthesis of biopolymers.

In dilute aqueous solution at pH = 4.3 in the presence of 0.1 M sodium dihydrogen phosphate, AOT (bis-(2-ethylhexyl)sulfosuccinate) was found to form vesicles. The average diameter of the vesicles was adjusted to about 70 nm by polycarbonate membrane extrusion. The vesicles were applied as chemical structure-controlling templates for the horseradish peroxidase/H2O2-triggered polymerization of aniline to yield the green emeraldine salt form of polyaniline. The enzyme-containing vesicular reaction system was optimized with respect to obtaining a reaction product with high absorbance in the NIR region of the spectrum which is known to be a characteristic property of the conductive emeraldine salt form of polyaniline. The reaction system was analyzed by cryo transmission electron microscopy, 1H NMR, UV/VIS/NIR, circular dichroism and fluorescence measurements. The peroxidase was found to be bound to the vesicles leading to an initiation of the reaction preferentially on the vesicles surface and not in the bulk aqueous solution. Before the reaction was started by H2O2 addition, the anilinium cations were found to only weakly interact with the surface of the vesicles. After polymerization, a stable suspension containing vesicles which were coated with polyaniline was obtained. The reaction product was isolated and analyzed by FTIR measurements. With respect to the vesicle system used previously, SDBS/decanoic acid (1:1) (Z. Guo, H. Ruegger, R. Kissner, T. Ishikawa, M. Willeke and P. Walde, Langmuir, 2009, 25, 11390–11405), the AOT system has several advantages for further explorations of this type of in situ formation of conductive vesicle-based polymer capsules.

We demonstrate that the catalyst Perkalite F100 efficiently works as a nanocatalyst in the depolymerization of poly(ethylene terephthalate) (PET). After depolymerization of PET in the presence of ethylene glycol and the Perkalite nanocatalyst, the main product obtained was bis(2-hydroxylethyl) terephthalate (BHET) with high purity, as confirmed by Fourier transform infrared spectroscopy and NMR. The BHET monomers could serve directly as starting materials in a further polymerization into PET with a virgin quality and contribute to a solution for the disposal of PET polymers. Compared with the direct glycolysis of PET, the addition of a predegradation step was shown to reduce the reaction time needed to reach the depolymerization equilibrium. The addition of the predegradation step also allowed lower reaction temperatures. Therefore, the strategy to include a predegradation step before depolymerization is suitable for increasing the efficiency of the glycolysis reaction of PET into BHET monomers. Funding details: MISTRA, Stiftelsen för Miljöstrategisk Forskning; Funding text: This work was financially supported by Mistra, the Swedish Foundation for Strategic Environmental Research.

The enzymatic polymerization of aniline to polyaniline (PANI) with Trametes versicolor laccase (TvL) as catalyst and dioxygen (O-2) as oxidant was investigated in an aqueous medium containing unilamellar vesicles with an average diameter of about 80 nm formed from AOT (=sodium bis(2-ethylhexyl) sulfosuccinate). Compared to the same reaction carried out with horseradish peroxidase isoenzyme C (HRPC) as catalyst and hydrogen peroxide (H2O2) as oxidant, notable differences were found in the kinetics of the reaction, as well as in the characteristics of the PANI obtained. Under comparable optimal conditions, which are pH 3.5 for TvL/O-2 and pH 4.3 for HRPC/H2O2, the reaction with TvL/O-2 was much slower than with HRPC/H2O2, i.e. approximate to 27 days vs. 1 day reaction time to reach equilibrium with >90% yield at 25 degrees C. Although in both cases, aniline monomer coupling occurred mainly via the carbon atom in para position of aniline, UV-vis-NIR absorption and EPR measurements indicate that the reaction with TvL/O-2 yielded mainly overoxidized products (with lambda(max) = 730 nm). These products had a lower amount of unpaired electrons if compared with the products obtained with HRPC/H2O2 (with lambda(max) approximate to 1000 nm, which is characteristic for the polaron state of PANI-ES, the emeraldine salt form of PANI). Similarly to previous findings with HRPC/H2O2, enzyme inactivation occurred during the polymerization also in the case of TvL/O-2. Since the aqueous PANI-vesicle suspensions obtained are of high colloidal stability, they can be used directly as ink in a conventional thermal inkjet printer for printing on paper or on surface treated polyimide films. Printed PANI-ES patterns on paper changed colour from green (emeraldine salt) to blue (emeraldine base) upon exposure to ammonia gas, demonstrating the expected ammonia sensing properties. (C) 2013 Elsevier Inc. All rights reserved

In this paper, the traditional fault location methods are analyzed, especially the C-type traveling wave location method; and a new composite method was presented which is based on traveling wave DC theory. The new method integrates the C-type of traveling wave location method with DC signal injection one. The aim is to combine different location methods to improve the accuracy of fault location. The new fault location method has two steps, the first step is determining the fault distance accurately by C-type of traveling wave location method; the second one is locating the fault branch by DC signal injection method. After theoretical analysis, ATP simulation, the composite location method is irrelevant to limits of the network dissymmetry, distributed capacitance and line parameter, can accurately determine the distribution network single-phase-to-earth fault location.

The feasibility of using surfactant vesicles as soft templates for the peroxidase-triggered polymerization of aniline was investigated. It was found that mixed anionic vesicles (diameter approximately 80 nm) composed of sodium dodecylbenzenesulfonate (SDBS) and decanoic acid (1:1, molar ratio) are promising templates. In the presence of the vesicles and horseradish peroxidase/hydrogen peroxide (H2O2) as initiator system, aniline polymerizes under optimized conditions at pH=4.3 to the desired conductive emeraldine form of polyaniline (PANI). The optimal polymerization conditions were elaborated, and some of the chemical and physicochemical aspects of the reaction system were investigated. After addition of aniline and peroxidase to the vesicles, aniline is only loosely associated with the vesicles, as shown by NOESY-NMR and zeta potential measurements. In contrast, the peroxidase strongly binds to the vesicle surface, as shown by fluorescence measurements using TNS (2-(p-toluidino)naphthalene-6-sulfonate) as vesicle membrane probe. This binding of the enzyme to the vesicle surface indicates that the polymerization reaction is initiated predominantly on the surface of the vesicles. Cryo-transmission electron microscopy indicates that the polymerization product remains associated with the vesicles on their surface. For short reaction times (30 s

On the basis of introducing the rural distribution networks of single-phase-to-earth fault location method, a composite of fault location method of single-phase earth fault about rural distribution network is presented which integrate C-type of traveling wave location method with DC signal injection method. There are two steps in this method, in which firstly the fault distance is accurately located by C-type of traveling wave location method; then the fault branch is located by DC signal injection method. The proposed composite location method gives full play to the advantage of high location speed of traveling wave location method and that of low location error of DC signal injection method and has a good application prospect.

The mechanism of the horseradish peroxidase (HRP)–H2O2-catalysed polymerisation of aniline in the presence of AOT vesicles was investigated. AOT (= bis-(2-ethylhexyl)sulfosuccinate) served as vesicle-forming surfactant and dopant for obtaining at pH = 4.3 and room temperature within 24 h under optimal reaction conditions the green emeraldine salt form of polyaniline in 90–95% yield. Based on UV/VIS/NIR and EPR measurements carried out during the polymerisation reaction, and based on changes in aniline and H2O2 concentrations and HRP activity, a mechanism is proposed. According to this “radical cation mechanism” chain growth occurs on the vesicle surface through addition of aniline radical cations to the growing polymer chain. H2O2 plays two essential roles, to oxidise the heme group of HRP, and to oxidise the growing polymer chain for allowing the stepwise addition of new aniline radical cations. The entire reaction can be divided into three kinetically distinct phases. In the first rapid phase (5–10 min), the actual polymer formation takes place to yield the emeraldine salt form of polyaniline in its bipolaron state. In the second and third slower phases (1–2 days) the bipolarons transform into polarons with unpaired electrons. During the reaction, the HRP activity is decreasing until the enzyme becomes inactive after polymer formation. Reactions carried out with partially deuterated anilines were analysed by 2H magic-angle spinning (MAS) NMR spectroscopy to demonstrate the regioselectivity of the chain growth: para-coupling of the aniline units clearly dominates. Association of the formed polyaniline with the vesicle membrane is evident from cryo-TEM and SANS measurements.