EDS analysis of Portland ash cement degradation in an aggressive environment

The behaviour of Portland cement with and without 30% fly ash addition in aggressive solutions was studied. This paper considers the sulphate corrosion of the hardened cement paste. The cement paste test samples were prepared, cured in water for 21 day and then exposed to the influence of aggressive environment (10% (NH₄SO₄ solution). The measurements of several properties were carried out and the results were analyzed.

The image of the surface composition and morphology of the cement paste test samples was made by scanning electron microscopy (SEM). Concentration gradient of sulphate ions in cement paste depth was obtained by energy‐dispersive analysis (EDS).     

Characterization of phosphogypsum wastes associated with phosphoric acid and fertilizers production

The present work is directed to characterize the phosphogypsum (PG) wastes associated with phosphoric acid produced by the wet process in industrial facility for the production of fertilizers and chemicals in Egypt. The PG waste samples were characterized in terms of spectroscopic analysis (X-ray diffraction, X-ray fluorescence, IR spectra) and radiometric analysis (γ- and α-measurements). The γ-ray measurements showed that the average activity concentrations are 140 ± 12.6, 459 ± 36.7, 323 ± 28.4, 8.3 ± 0.76 and 64.3 ± 4.1 Bq/kg for U-238, Ra-226, Pb-210, Th-232 and K-40, respectively. The α-particle measurements of uranium isotopes showed that the average activity concentrations of U-238, U-235 and U-234 were 153 ± 9.8, 7 ± 0.38, 152 ± 10.4 Bq/kg, respectively. The average radiochemical recovery (%) of the destructive α-particle measurements is ∼70% with a resolution (FWHM) of ∼30 keV. Activity ratios of U-238/Ra-226 and U-238/Pb-210 were less than unity (i.e., <1) and equal to 0.31 ± 0.02 and 0.47 ± 0.16, respectively. The isotopic ratios of U-238/U-235 and U-238/U-234 (in PG and PR samples) were close to the normal values of ∼21.7 and ∼1, respectively and are not affected by the wet processing of phosphate rock (PR). The obtained results of PG waste samples were compared with phosphate rock (PR) samples. The radiation hazard indices are namely, radium activity index (Ra-Eq > 370 Bq/kg), total absorbed gamma dose rate (D_γr > 5 nGy/h) and radon emanation fraction (Rn-EF > 20%). Uncertainty of the sample counting was 95% confidence level of σ. The results indicated the necessity to find suitable routes to decrease and/or redistribute the radionuclide of environmental interest (i.e., Ra-226) in PG wastes, consequently to reduce its radiation impacts in the surrounding environment.     

论小城镇核心竞争力的构建和提升

小城镇作为中国城镇化进程的重要组成部分,对于我国城镇发展的作用举足轻重.研究我国小城镇的核心竞争力问题,有助于加深对小城镇经济发展的认识,帮助政府部门从更高的层次制定小城镇经济发展战略.本文界定了小城镇核心竞争力的概念,探讨了培育和提升小城镇经济核心竞争力的重要意义,并从自然环境、人文环境、基础设施、软件环境、创新能力及产业集群等方面对小城镇核心竞争力的构成进行分析;针对小城镇核心竞争力的构建和提升,提出了优化小城镇发展环境,完善小城镇创新体系,增强小城镇产业集群的发展等建议;得出了发展小城镇经济的关键是要增强其竞争力,而要保持小城镇经济持续的竞争优势,关键在于小城镇经济核心竞争力的培育和提升的结论,为促进我国小城镇经济的持续、快速发展及核心竞争力的构建与提升提供参考和借鉴.     

长株潭城市群核心区大气环境承载力初探

对长株潭城市群核心区大气环境质量现状进行了分析,评价了长株潭城市群核心区大气环境承载力,分析了长株潭核心区大气环境承载力发展趋势,提出了提高长株潭核心区大气环境承载力利用水平的建议。     

对社会主义核心价值体系建设几个问题的探讨

从阐述相关基本概念入手,系统分析人类社会核心价值体系的嬗变历程和社会主义核心价值体系的科学内涵;阐述了建设社会主义核心价值体系的历史必然性,进而提出了弘扬和践行社会主义核心价值体系的方法和途径。     

电子产品共振频率检测方法研究

本文介绍了电子产品共振频率检测方法,主要有目测法、正弦扫描法、随机振动法和模态分析法,并结合工程案例对几种方法进行描述。     

Application of an early warning indicator and CaO to maximize the time–space-yield of an completely mixed waste digester using rape seed oil as co-substrate

In order to increase the organic loading rate (OLR) and hereby the performance of biogas plants an early warning indicator (EWI-VFA/Ca) was applied in a laboratory-scale biogas digester to control process stability and to steer additive dosing. As soon as the EWI-VFA/Ca indicated the change from stable to instable process conditions, calcium oxide was charged as a countermeasure to raise the pH and to bind long-chain fatty acids (LCFAs) by formation of aggregates. An interval of eight days between two increases of the OLR, which corresponded to 38% of the hydraulic residence time (HRT), was sufficient for process adaptation. An OLR increase by a factor of three within six weeks was successfully used for biogas production. The OLR was increased to 9.5 kg volatile solids (VS) m^?3 d^?1 with up to 87% of fat. The high loading rates affected neither the microbial community negatively nor the biogas production process. Despite the increase of the organic load to high rates, methane production yielded almost its optimum, amounting to 0.9 m³ (kg VS)^?1. Beneath several uncharacterized members of the phylum Firmicutes mostly belonging to the family Clostridiaceae, a Syntrophomonas-like organism was identified that is known to live in a syntrophic relationship to methanogenic archaea. Within the methanogenic group, microorganisms affiliated to Methanosarcina, Methanoculleus and Methanobacterium dominated the community.     

火灾下空心混凝土楼板内温度场分析模型及算法

计算火灾下空心混凝土楼板内温度场的关键是计算空腔内的热量传递。假设火灾过程中空腔内气体压力为常数,空气流动引起的热量损失忽略不计,空腔内的热量传递通过壁面辐射和空气传导实现。基于奥本海姆网络法,本文提出了计算空心混凝土楼板空腔内辐射热流的算法,推导了矩阵形式的空腔内有效辐射方程,考虑到系数矩阵的对称性,采用LDLT分解法求解有效辐射方程。利用空腔边界上的有效辐射热流,计算空腔边界上单元的温度节点荷载。这种方法已经嵌入作者开发的温度场分析软件TFIELD之中,用TFIELD对底面按ISO834曲线进行加热的空心混凝土楼板进行计算,结果表明,本文算法十分有效,对研究空心混凝土楼板的抗火性能具有积极意义。     

Chlorination-induced cellular damage and recovery in marine microalga, Chlorella salina

Power plants employ chlorination for controlling biofouling in the cooling water system. Phytoplankton drawn into the cooling water system could be impacted by chemical stress induced by the oxidizing biocide. It is likely that microalgae, being sensitive to chlorine, could suffer damage to their cellular structure and function. In this study, we present data on the effect of in-use concentrations of chlorine on the unicellular microalga, Chlorella salina. Chlorophyll autofluorescence was measured in terms of mean fluorescence intensity per cell for rapid assessment of toxicity. Viability of the cells exposed to chlorine was determined by fluorescein diacetate staining. Functionality of the photosynthetic machinery was assessed by gross primary productivity. Results from the study, which combined confocal laser scanning microscopy with image analysis, showed a significant dose-dependant reduction in chlorophyll autofluorescence, esterase activity and gross primary productivity in chlorine-treated cells. Interestingly, the cells injured by chlorination could not recover in terms of autofluorescence, esterase activity or productivity even after 18 h incubation in healthy media. Among the test points evaluated, esterase activity appeared to be sensitive for determining the chlorination-induced impact. Our results demonstrate that low-dose chlorination causes significant decrease in chlorophyll autofluorescence, intracellular esterase activity and primary productivity in Chlorella cells.     

光纤传导可见光降解亚甲基蓝

针对浓度大、色度高的印染废水难以处理的情况,选用加入光纤的光催化体系进行研究。采用溶胶凝胶法制备了Ag+/TiO2粉体光催化剂,用固体紫外可见光谱、X射线衍射对其进行表征。选用亚甲基蓝溶液作为目标降解物,评价了Ag+/TiO2在可见光下的光催化活性。分别考察了加入石英芯侧光光纤与塑料侧光光纤反应体系下,催化剂量、光纤数量、光照强度和pH值等因素对亚甲基蓝降解实验的影响。结果表明,选用20 mg/L的亚甲基蓝,采用催化剂量为11.67 g/L,500根侧光光纤,300 W的外部光源,pH值约为11时,光催化降解效果最佳,均能达到90%以上。