全尺寸交流500 kV输电杆塔复合横担的雷电闪络特性

架空输电线路(OTL)一直以来都是电力传输的主要方式。随着输电电压和输电容量的迅速提高,输电杆塔的尺寸也随之增加,造成土地资源的大量占用。考虑到线路复合绝缘子的优异性能,复合横担有望成为这一问题的解决方案。在本文中,作者制备了一个安装有复合横担的全尺寸交流(AC)500 kV输电杆塔,并施加了不同极性的雷电过电压。借助高速相机记录了流注-先导放电的过程,确认了闪络的主要路径。通过测量闪络电压并根据空气密度和湿度对结果进行修正,证实了放电的极性效应。继而,根据杆塔结构和闪络特性计算了杆塔的耐雷水平。基于全尺寸试验的结果与分析,确认了复合横担的可行性,并提出了结构优化方案。

Equipment selection knowledge base system for industrial styrene process

Equipment selection for industrial process usually requires the extensive participation of industrial experts and technologists, which causes a serious waste of resources. This work presents an equipment selection knowledge base system for industrial styrene process(S-ESKBS) based on the ontology technology. This structure includes a low-level knowledge base and a top-level interactive application. As the core part of the S-ESKBS, the low-level knowledge base consists of the equipment selection ontology library, equipment selection rule set and Pellet inference engine. The top-level interactive application is implemented using S-ESKBS, including the parsing storage layer, inference query layer and client application layer. Case studies for the industrial styrene process equipment selection of an analytical column and an alkylation reactor are demonstrated to show the characteristics and implementability of the S-ESKBS.

ZIF-7@carbon composites as multifunctional interlayer for rapid and durable Li-S performance

The notorious"shuttle effect"of polysulfide during charge-discharge process induces grievous capacity fading,while the sluggish polysulfide conversion kinetics significantly hinders the development of practically viable lithium-sulfur(Li-S)batteries.In this study,a novel ZIF-7@carbon composite with ZIF-7 sheets vertically rooted on carbon cloth was developed as multifunctional interlayer to address these issues.The composite shows directional layered structure with outstanding compactness,and thus can provide massive active sites for accelerated redox reactions.The pore channels are perpendicular to the square surface,resulting in extremely high utilization of one-dimensional channels.Therefore,this structure can not only maintain the structural stability during the charge-discharge process by providing enough space for volume expansion,but also contribute to efficient exposure and utilization of active sites for the physical/chemical adsorption and catalytic conversion of polysulfide.As a result,Li-S batteries with the as-developed interlayer deliver a considerable areal capacity of 4.75 mAh cm^(-2) at an elevated sulfur loading of 5.5 mg cm^(-2),and an impressive cyclability with an extremely low capacity-fading rate of merely 0.04%per cycle over 500 cycles at 1 C.

Local Discontinuous Galerkin Scheme for Space Fractional Allen–Cahn Equation

This paper is concerned with the efficient numerical solution for a space fractional Allen–Cahn(AC)equation.Based on the features of the fractional derivative,we design and analyze a semi-discrete local discontinuous Galerkin(LDG)scheme for the initial-boundary problem of the space fractional AC equation.We prove the optimal convergence rates of the semi-discrete LDG approximation for smooth solutions.Finally,we test the accuracy and efficiency of the designed numerical scheme on a uniform grid by three examples.Numerical simulations show that the space fractional AC equation displays abundant dynamical behaviors.

Recycling valuable cobalt from spent lithium ion batteries for controllably designing a novel sea-urchin-like cobalt nitride-graphene hybrid catalyst: Towards efficient overall water splitting

Along with the continuous consumption in lithium-ion batteries (LIBs), the price of cobalt is inevitably going up in recent years. Therefore, recycling valuable Co element from spent devices, and boosting its service efficiency are becoming two indispensable approaches to promote the utilization of Co in various energy conversion/storage devices. Herein, we realize the recovery of Co from spent LIBs and synthesize a three–dimensional (3D) sea-urchin-like cobalt nitride composite material (labeled as CoN-Gr-2), which is used as a bi-functional catalyst for water splitting. Benefiting from the intrinsic high conductivity, larger surface area and unique 3D sea–urchin–like architecture, CoN-Gr-2 shows an excellent electron transfer efficiency, highly exposed active sites as well as the superior mass transport capacity. The CoN-Gr-2 catalyst exhibits low overpotentials of 128.9 mV and 280 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which are comparable to the commercial 20 wt% Pt/C and RuO_(2) catalysts. Moreover, when adopting CoN-Gr-2 as both anode and cathode materials for overall water splitting (in 1.0 M KOH electrolyte), the assembled cell achieves a current density of 10 mA cm^(−2) at 1.61 V, which almost close to that of Pt/C||RuO_(2) benchmark (1.60 V), demonstrating its superior water-splitting efficiency. Meanwhile, the CoN catalysts exhibit strong chemical interaction with the Gr support, suppressing the aggregation of CoN catalysts and maintains their high activity during HER and OER reactions. So, the cell exhibits a high current retention of 97.3% after 40 h. This work successfully develops an industrial chain from recycling Co wastes in spent energy devices to controllably designing 3D sea-urchin-like CoN-Gr with high water splitting efficiency. Therefore, it could further promote the efficient utilization of valuable Co element in various energy devices.

Rational design of Co nano-dots embedded three-dimensional graphene gel as multifunctional sulfur cathode for fast sulfur conversion kinetics

Lithium-sulfur(Li-S)batteries hold great promises to serve as next-generation energy storage devices because of their high theoretical energy density and environmental benignity.However,the shuttle effect of the soluble lithium polysulfides(LiPS)and intrinsic insulating nature of sulfur lead to low sulfur utilization and coulombic efficiency,leading to poor cycling performance.The impeded charge transportation and retard LiPS catalytic conversion also endows the Li-S batteries with sluggish redox reaction,leading to unsatisfied rate capability.In this study,Co-based MOF material ZIF-67 is used as the precursor to prepare Co nano-dots decorated three-dimensional graphene aerogel as sulfur immobilizer.This porous architecture establishes a highly conductive interconnected framework for fast charge/mass transportation.The exposed Co nano-dots serve as active sites to strongly trap LiPS,which endows CoNDs@G with low decomposition energy barrier for fast LiPS conversion reaction and promote the completely Li2 S catalytic transformation.Li-S cells based on the Co-NDs@G cathode exhibits excellent cyclability and a high capacity retention rate of 91.1%in 100 cycles.This strategy offers a new direction to design sulfur immobilizer for accelerated LiPS conversion kinetics of Li-S batteries.

Inhibiting liquid permeation into silicone rubber by superhydrophobic coating for prolonged service life

Liquid permeation into silicone rubber(SR)may lead to the degradation or complete failure of the composite insulators.Aiming to inhibit liquid permeation,two kinds of superhydrophobic coatings are applied to the SR surface.The liquid permeation properties of SR with different types of liquids are investigated,and the Langmuir diffusion model is applied to analyse the experimental data.The results show that the composite superhydrophobic coating can effectively inhibit liquid permeation by reducing the contact area between the surface and liquid,and the stable structure of the composite coating can maintain the performance after the liquid permeation and effusion.However,the nano‐particle coating without the polymer binder experiences severe performance degradation during the immersion test,and it cannot restrain the liquid permeation anymore after it loses the superhydrophobicity.As a validation of the effective protection,the insulation resistivity change was measured.The resistivity decreases sharply for the pristine SR after water permeation;however,the decrease is much smaller for the coated SR.The current study not only provides new insight into the liquid permeation properties of SR with different surface wettability but also suggests an effective measure to prevent liquid permeation into SR.

Monthly survey of N-nitrosamine yield in a conventional water treatment plant in North China

A sampling campaign was conducted monthly to investigate the occurrence of N-nitrosamines at a conventional water treatment plant in one city in North China.The yield of N-nitrosamines in the treated water indicated precursors changed greatly after the source water switching.Average concentrations of N-nitrosodimethylamine（NDMA）,N-nitrosomorpholine（NMOR）,and N-nitrosopyrrolidine（NPYR） in the finished water were6.9,3.3,and 3.1 ng/L,respectively,from June to October when the Luan River water was used as source water,while those of NDMA,N-nitrosomethylethylamine（NMEA）,and NPYR in the finished water were 10.1,4.9,and 4.7 ng/L,respectively,from November to next April when the Yellow River was used.NDMA concentration in the finished water was frequently over the 10 ng/L,i.e.,the notification level of California,USA,which indicated a considerable threat to public health.Weak correlations were observed between N-nitrosamine yield and typical water quality parameters except for the dissolved organic nitrogen.

A red water occurrence in drinking water distribution systems caused by changes in water source in Beijing, China： mechanism analysis and control measures

A red water phenomenon occurred in several communities few days after the change of water source in Beijing, China in 2008. In this study, the origin of this problem, the mechanism of iron release and various control measures were investigated. The results indicated that a significant increase in sulphate concentration as a result of the new water source was the cause of the red water phenomenon. The mechanism of iron release was found that the high-concentration sulphate in the new water source disrupted the stable shell of scale on the inner pipe and led to the release of iron compounds. Experiments showed that the iron release rate in the new source water within pipe section was over 11-fold higher than that occurring within the local source water. The recovery of tap water quality lasted several months despite ameliora- tive measures being implemented, including adding phosphate, reducing the overall proportion of the new water source, elevating the pH and alkalinity, and utilizing free chlorine as a disinfectant instead of chloramine. Adding phosphate was more effective and more practical than the other measures. The iron release rate was decreased after the addition of 1.5 mg. L-1 orthophosphate- P, tripolyphosphate-P and hexametaphosphate-P by 68%, 83% and 87%, respectively. Elevating the pH and alkalinity also reduced the iron release rate by 50%. However, the iron release rate did not decreased after replacing chloramine by 0.5-0.8 mg. L-1 of free chlorine as disinfectant.

Using loose nanofiltration membrane for lake water treatment:A pilot study

Nanofiltration(NF)using loose membranes has a high application potential for advanced treatment of drinking water by selectively removing contaminants from the water,while membrane fouling remains one of the biggest problems of the process.This paper reported a seven-month pilot study of using a loose NF membrane to treat a sand filtration effluent which had a relatively high turbidity(∼0.4 NTU)and high concentrations of organic matter(up to 5 mg/L as TOC),hardness and sulfate.Results showed that the membrane demonstrated a high rejection of TOC(by<90%)and a moderately high rejection of two pesticides(54%–82%)while a moderate rejection of both calcium and magnesium(∼45%)and a low rejection of total dissolved solids(∼27%).The membrane elements suffered from severe membrane fouling,with the membrane permeance decreased by 70%after 85 days operation.The membrane fouling was dominated by organic fouling,while biological fouling was moderate.Inorganic fouling was mainly caused by deposition of aluminum-bearing substances.Though inorganic foulants were minor contents on membrane,their contribution to overall membrane fouling was substantial.Membrane fouling was not uniform on membrane.While contents of organic and inorganic foulants were the highest at the inlet and outlet region,respectively,the severity of membrane fouling increased from the inlet to the outlet region of membrane element with a difference higher than 30%.While alkaline cleaning was not effective in removing the membrane foulants,the use of ethylenediamine tetraacetate(EDTA)at alkaline conditions could effectively restore the membrane permeance.

Improvement of the assimilable organic carbon （AOC） analytical method for reclaimed water

Microbial growth is an issue of concern that may cause hygienic and aesthetic problems during the transportation and usage of reclaimed water. Assimilable organic carbon （AOC） is an important parameter which determines the heterotrophic bacterial growth potential of water. Pseudomonas fluorescens P17 and Spirillum sp. NOX are widely used to measure AOC in drinking water. The AOC values of various reclaimed water samples determined by P 17 and NOX were compared with those determined by the new strains isolated from reclaimed water in this study. It showed that the conventional test strains were not suitable for AOC measurement of reclaimed water in certain cases. In addition to P17 and NOX, Stenotrophomonas sp. Z J2, Pseudomonas saponi- phila G3 and Enterobacter sp. G6, were selected as test strains for AOC measurement of reclaimed water. Key aspects of the bioassay including inoculum cell density, incubation temperature, incubation time and the pH of samples were evaluated for the newly selected test strains. Higher inoculum density （104 CFU.mL-1） and higher incubation temperature （25℃） could reduce the time required for the tests. The AOC results of various collected samples showed the advantages of the method proposed based on those five strains in evaluating the biologic stability of reclaimed water.

Review on corrosion and corrosion scale formation upon unlined cast iron pipes in drinking water distribution systems

The qualified finished water from water treatment plants(WTPs) may become discolored and deteriorated during transportation in drinking water distribution systems(DWDSs), which affected tap water quality seriously. This water stability problem often occurs due to pipe corrosion and the destabilization of corrosion scales. This paper provides a comprehensive review of pipe corrosion in DWDSs, including corrosion process, corrosion scale formation, influencing factors and monitoring technologies utilized in DWDSs. In terms of corrosion process, corrosion occurrence, development mechanisms, currently applied assays, and indices used to determine the corrosion possibility are summarized, as well as the chemical and bacterial influences. In terms of scale formation, explanations for the nature of corrosion and scale formation mechanisms are discussed and its typical multilayered structure is illustrated. Furthermore, the influences of water quality and microbial activity on scale transformation are comprehensively discussed. Corrosion-related bacteria at the genus level and their associated corrosion mechanism are also summarized. This review helps deepen the current understanding of pipe corrosion and scale formation in DWDSs, providing guidance for water supply utilities to ensure effective measures to maintain water quality stability and guarantee drinking water safety.

Water quality induced corrosion of stainless steel valves during long-term service in a reverse osmosis system

The current study analyzes the contribution of 10 water quality parameters(including pH,turbidity,conductivity,total dissolved solids(TDS),hardness,total organic carbon(TOC),alkalinity,calcium ions,chlorides and sulfates) to corrosion extent of stainless steel valves taken from different locations in a reverse osmosis system of a reclaimed water plant.The valves were in service for 5 years.Raman spectroscopy and X-ray photoelectron spectroscopy analyses are conducted to quantify corrosion products on different valves under various water quality conditions.On that basis,bivariate and multivariate regression analyses between the 10 water quality parameters and the corrosion extent of valve specimens(represented by metal loss percentage(MLP) values) are carried out to check the contribution of those water quality parameters to MLP.The results indicate that the proportions of metal oxides as corrosion products vary according to the corrosion extent of the valves.Although no linear correlation is founds all 10 water quality parameters except for pH show a significant positive correlation with the MLP values of the valve specimens.Moreover,results of multivariate regression suggest that the variation of MLP can be explained by turbidity,TDS,TOC and sulfates.A positive contribution of turbidity,TDS and TOC to MLP is observed,whereas the contribution of sulfates is negative.The results from the current work help to identify the reasons for water quality-induced failure of stainless steel equipment in RO systems.

Effect of different molecular weight organic components on the increase of microbial growth potential of secondary effluent by ozonation

Ozonation has been widely applied in advanced wastewater treatment. In this study, the effect of ozonation on assimilable organic carbon （AOC） levels in secondary effluents was investigated, and AOC variation of different molecular weight （MW） organic components was analyzed. Although the removal efflciencies were 47%-76% and 94%-100% for UV2s4 and color at ozone dosage of 10 mg/L, dissolved organic carbon （DOC） in secondary effluents was hardly removed by ozonation. The AOC levels increased by 70%-780% at an ozone dosage range of 1-10 mg/L. AOC increased significantly in the instantaneous ozone demand phase, and the increase in AOC was correlated to the decrease in UV254 during ozonation. The results of MW distribution showed that, ozonation led to the transformation of larger molecules into smaller ones, but the increase in low MW （〈1 kDa） fraction did not contribute much to AOC production. The change of high MW （〉100 kDa and 10-100 kDa） fractions itself during ozonation was the main reason for the increase of AOC levels. Furthermore, the oxidation of organic matters with high MWs （〉 100 kDa and 10-100 kDa） resulted in more AOC production than those with low MWs （1-10 kDa and 〈1 kDa）. The results indicated that removing large molecules in secondary effluents could limit the increase of AOC during ozonation.

Decision Support System for emergency scheduling of raw water supply systems with multiple sources

A hydraulic model-based emergency schedul- ing Decision Support System （DSS） is designed to eliminate the impact of sudden contamination incidents occurring upstream in raw water supply systems with multiple sources. The DSS consists of four functional modules, including water quality prediction, system safety assessment, emergency strategy inference and scheduling optimization. The work flow of the DSS is as follows. First, the water quality variations on specific cross-sections are calculated given the pollution information. Next, a comprehensive evaluation on the safety of the current system is conducted using the outputs in the first module. This will assist in the assessment of whether the system is in danger of failure, taking both the impact of pollution and system capacity into account. If there is a severe impact of contamination on the reliability of the system, a fuzzy logic based inference module is employed to generate reason- able strategies including technical measures. Otherwise, a Genetic Algorithm （GA）-based optimization model will be used to find the least-cost scheduling plan. The proposed DSS has been applied to a coastal city in South China during a saline tide period as validation. Through scenario analysis, it is demonstrated that this DSS tool is instrumental in emergency scheduling for the water company to quickly and effectively respond to sudden contamination incidents.

Stainless steel corrosion scale formed in reclaimed water： Characteristics, model for scale growth and metal element release

Stainless steels generally have extremely good corrosion resistance, but are still susceptible to pitting corrosion. As a result, corrosion scales can form on the surface of stainless steel after extended exposure to aggressive aqueous environments. Corrosion scales play an important role in affecting water quality. These research results showed that interior regions of stainless steel corrosion scales have a high percentage of chromium phases. We reveal the morphology, micro-structure and physicochemical characteristics of stainless steel corrosion scales. Stainless steel corrosion scale is identified as a podiforrn chromite deposit according to these characteristics, which is unlike deposit formed during iron corrosion. A conceptual model to explain the formation and growth of stainless steel corrosion scale is proposed based on its composition and structure. The scale growth process involves pitting corrosion on the stainless steel surface and the consecutive generation and homogeneous deposition of corrosion products, which is governed by a series of chemical and electrochemical reactions. This model shows the role of corrosion scales in the mechanism of iron and chromium release from pitting corroded stainless steel materials. The formation of corrosion scale is strongly related to water quality parameters. The presence of HCIO results in higher ferric content inside the scales. Cl- and SO2- ions in reclaimed water play an important role in corrosion pitting of stainless steel and promote the formation of scales.

Comparison of different combined treatment processes to address the source water with high concentration of natural organic matter during snowmelt period

The source water in one forest region of the Northeast China had very high natural organic matter（NOM） concentration and heavy color during snowmelt period. The efficiency of five combined treatment processes was compared to address the high concentration of NOM and the mechanisms were also analyzed. Conventional treatment can hardly remove dissolved organic carbon（DOC） in the source water. KMn O4pre-oxidization could improve the DOC removal to 22.0%. Post activated carbon adsorption improved the DOC removal of conventional treatment to 28.8%. The non-sufficient NOM removal could be attributed to the dominance of large molecular weight organic matters in raw water, which cannot be adsorbed by the micropore upon activated carbon. O3＋ activated carbon treatment are another available technology for eliminating the color and UV254 in water. However, its performance of DOC removal was only 36.4%, which could not satisfy the requirement for organic matter. The limited ozone dosage is not sufficient to mineralize the high concentration of NOM. Magnetic ion-exchange resin combined with conventional treatment could remove 96.2%of color, 96.0% of UV254 and 87.1% of DOC, enabling effluents to meet the drinking water quality standard. The high removal efficiency could be explained by the negative charge on the surface of NOM which benefits the static adsorption of NOM on the anion exchange resin. The results indicated that magnetic ion-exchange resin combined with conventional treatment is the best available technology to remove high concentration of NOM.

Non-destructive thermal ageing evaluation of P(VDF-HFP)film based on broadband dielectric response

Capacitors and sensors based on polymer dielectric materials are key components in electrical systems and electronic devices.Considering the temperature rise during operation,an effective evaluation method for the thermal ageing of polymer matrix is urgently needed.P(VDF-HFP)film with a thickness of 20μm is manufactured by solution casting and a thermal ageing experiment up to 1000 h is conducted.Dielectric responses of wide ranges of temperatures and frequencies are measured for samples with different ageing durations.The universal relaxation law and Dissado–Hill dielectric response model are applied to further investigate the results.The characteristics of individual processes are obtained,which demonstrate that the main chain relaxation following the Vogel−Fulcher−Tammann equation and side chain relaxation following the Arrhenius equation both remain unchanged after thermal ageing.However,the activation energies of those two processes change significantly during the process and show different variation trends.The activation energy of the side chain relaxation gets larger monotonically due to the influence of annealing and the breaking of crystalline region.As a result,a non-destructive evaluation method for the thermal ageing of P(VDF-HFP)is proposed accordingly.

Aniline Induced Domino Ring Contraction Process on the Rim of an Open-Cage Fullerene with Carbonyl, Imino and lactone Moieties

Functional groups on the rim of open-cage fullerenes usually exhibit different reactivity from those in classical organic molecules due to the unique spherical structure of fullerenes.The present work shows a sequence of lactone opening,imino hydrolysis,aminal formation and imine formation processes during the reaction of aniline with the open-cage compound 1 with functional groups including lactone on the rim of the orifice.Single crystal X-ray diffraction analysis confirmed the structure of the product.