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101.
In keyhole plasma arc welding (PAW), the formation of the keyhole involves complicated thermo-physical mechanism. The shape and dimensions of the keyhole directly determine the heat deposition along the thickness direction of the test plates, the penetration depth and the weld bead quality. Based on analysis of the forces acting on the weld pool, a keyhole model is established according to the force-balance condition on the keyhole wall. The shape and dimensions of quasi-steady state keyhole are numerically predicted. The keyhole shape and size are used to calibrate some distribution parameters of the combined volumetric heat source which takes into consideration the geometrical feature of welds with larger ratio of penetration depth to width and volumetric distribution characteristic of the plasma heat intensity along the plate thickness direction. The temperature fields on stainless steel plates are numerically simulated. The calculated fusion line at the transverse cross-section of PAW welds are compared with the experimental measurements. It is found that the predicted results are in agreement with the experimental data. 相似文献
102.
Congrui Deng Guochen Wang Kan Huang Qingyan Fu Jia Chen Juntao Huo Qianbiao Zhao Yusen Duan Yanfen Lin Fan Yang Wenjie Zhang Hao Li Jian Xu Xiaofei Qin Na Zhao 《环境科学学报(英文版)》2022,34(12):115-127
The coronavirus (COVID-19) pandemic is disrupting the world from many aspects. In this study, the impact of emission variations on PM2.5-bound elemental species and health risks associated to inhalation exposure has been analyzed based on real-time measurements at a remote coastal site in Shanghai during the pandemic. Most trace elemental species decreased significantly and displayed almost no diel peaks during the lockdown. After the lockdown, they rebounded rapidly, of which V and Ni even exceeded the levels before the lockdown, suggesting the recovery of both inland and shipping activities. Five sources were identified based on receptor modeling. Coal combustion accounted for more than 70% of the measured elemental concentrations before and during the lockdown. Shipping emissions, fugitive/mineral dust, and waste incineration all showed elevated contributions after the lockdown. The total non-carcinogenic risk (HQ) for the target elements exceeded the risk threshold for both children and adults with chloride as the predominant species contributing to HQ. Whereas, the total carcinogenic risk (TR) for adults was above the acceptable level and much higher than that for children. Waste incineration was the largest contributor to HQ, while manufacture processing and coal combustion were the main sources of TR. Lockdown control measures were beneficial for lowering the carcinogenic risk while unexpectedly increased the non-carcinogenic risk. From the perspective of health effects, priorities of control measures should be given to waste incineration, manufacture processing, and coal combustion. A balanced way should be reached between both lowering the levels of air pollutants and their health risks. 相似文献
103.
为了解山西省城市居民对室内空气质量安全的认知情况和室内空气质量现状,在山西省太原、大同、晋城和吕梁随机选取786户居民进行问卷调查,并对有检测意愿的86户居民进行室内甲醛含量检测.结果表明,山西省居民室内空气质量安全认知得分15.37,得分率为51%;山西省居民平均室内甲醛浓度(0.197 mg/m3)超过国家标准(0.1 mg/m3);四市中太原市的情况最好.山西省居民在室内空气质量安全方面的认知水平和室内空气质量都不高,为保障山西省居民健康,应对山西省城市居民进行室内空气质量安全知识的普及. 相似文献
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105.
以广东省21个地级市为研究对象,根据低碳发展理念与目标,结合广东省的低碳发展路径,选取与低碳城市发展密切相关的14个基础指标,构建广东省低碳城市评价指标体系进行综合评价。结果表明:(1)广东省低碳城市评价较好的城市主要有广州、深圳、珠海、佛山、惠州等。(2)参与评价的城市得分均较高,整体上具备良好发展势头。(3)排名越靠后的城市,制约指标越多,新能源与可再生能源比例是广东省低碳发展最受制约的指标。(4)单位土地面积碳排放量指标各城市间的反差最大,主要是由于各城市的市域面积不一,能源消费与经济发展不平均而造成的。 相似文献
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107.
Abstract The aim of this study was to investigate the mechanism of cadmium (Cd) adsorbed by microalgae Chlamydomonas reinhardtii (C.reinhardtii). The kinetic and adsorption isotherm of the process could be well described by mathematical models. Chemical modification experiments and Fourier transform infrared spectra indicated that carboxyl and amine groups were the important functional groups for adsorption of Cd. The maximum contribution of physical adsorption in the overall adsorption process was evaluated as 5.5%. These results indicated that chemisorption was the dominating mechanism of Cd biosorption by C.reinhardtii. 相似文献
108.
Li Songqing Raza Ali Si Ruishi Huo Xuexi 《Environmental science and pollution research international》2022,29(59):89014-89028
Environmental Science and Pollution Research - Recently, The literature has directed concern towards the consumption-based carbon emission (CCE), which is adjusted for trade. This study aims to... 相似文献
109.
Microcystis aeruginosa is a common aquatic toxin-producing cyanobacterium. This study explores M. aeruginosa biomass recovery using bioflocculation. Bioflocculants produced by Klebsiella pneumoniae significantly enhanced aquatic M. aeruginosa flocculation efficiency. Under neutral and acidic conditions, flocculation efficiency reached 90%, whereas flocculation efficiency was 75% under alkaline conditions. M. aeruginosa flocculation was ion dependent, and Ca2+ was determined to be the most effective cationic inducer. Negatively charged proteoglycans were identified as the being the functional components in the flocculants. Optimal conditions for M. aeruginosa flocculation were determined using response surface methodology and are as follows: (1) K. pneumoniae bioflocculant dose, 13.3?mg/L; (2) flocculation time, 1.6 hours; and (3) pH?=?5 for flocculation of 109 cells per litre. Bioflocculation using K. pneumoniae represents a promising method to control development of M. aeruginosa blooms. Further in-field investigations are necessary to fully assess its potential. 相似文献
110.
Juntao HUO Xiaohui LU Xinning WANG Hong CHEN Xingnan YE Song Gao Deborah S. Gross Jianmin CHEN Xin YANG 《Frontiers of Environmental Science & Engineering》2016,10(2):244-252
Fresh straw burning (SB) particles were generated in the laboratory by the combustion of rice straw and corn straw. The chemical composition and mixing state of the fresh SB particles were investigated by an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS). Based on the mass spectral patterns, the SB particles were clustered into four major types: Salt, Organic Carbon (OC), Elemental Carbon (EC), and internally mixed particles of EC and OC (EC-OC). In addition, particles containing ash, polycyclic aromatic hydrocarbons, heavy metals or nicotine were also observed. Physical and chemical changes of the SB particles immediately after the emission were analyzed with highly time-resolved data. During the aging processes, the average particle size increased steadily. Freshly emitted organic compounds were gradually oxidized to more oxygenated compounds in the OC-containing particles. Meanwhile, an important displacement reaction (2KCl+ S O 4 2 − → K2SO4 + 2Cl−) was observed. The marker ions for SB particles were optimized and applied to identify the SB particles in the ambient atmosphere. The fluctuation of the number fraction of ambient SB particles sorted by ATOFMS agrees well with that of water soluble K+ measured by an online ion chromatography, demonstrating that the optimized marker ions could be good tracers for SB particles in field measurements. 相似文献