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721.
Significant iron release from cast iron pipes in water distribution systems (WDSs), which usually occurs during the source water switch period, is a great concern of water utilities because of the potential occurrence of “red water” and customer complaints. This study developed a new method which combined in-situ water stagnation experiments with mathematical models and numerical simulations to predict the iron release caused by source water switch. In-situ water stagnation experiments were conducted to determine the total iron accumulation in nine cast iron pipes in-service in Beijing when switching the local water to treated Danjiangkou Reservior water. Results showed that the difference in the concentration increment of total iron in 24 hr (ΔCITI,24), i.e. short-term iron release, caused by source water switch was mainly dependent on the difference in the key quality parameters (pH, hardness, nitrate, Larson Ratio and dissolved oxygen (DO)) between the two source waters. The iron release rate (RFe) after switch, i.e. long-term iron release, was closely related to the pipe properties as well as the DO and total residual chlorine (TRC) concentrations. Mathematical models of ΔCITI,24 and RFe were developed to quantitatively reveal the relationship between iron release and the key quality parameters. The RFe model could successfully combine with EPANET-MSX, a numerical simulator of water quality for WDSs to extend the iron release modeling from pipe level to network level. The new method is applicable to predicting iron release during source water switch, thus facilitating water utilities to take preventive actions to avoid “red water”. 相似文献
722.
723.
利用造纸污泥灰和生活污泥灰替代部分水泥制备胶凝材料,研究了污泥灰掺量对污泥灰-水泥胶凝体系力学性能的影响,采用X射线衍射、红外光谱、扫描电镜和能谱分析手段对胶凝体系水化产物的矿物组成、化学结构及微观形貌进行研究。结果表明,随着污泥灰掺量增加,胶凝体系抗压强度不断降低,当污泥灰掺量超过40%,试样3 d抗压强度比小于5%。当水泥掺量一定,提高造纸污泥灰的掺加比例有利于胶凝体系早期强度的增长,生活污泥灰可有效提高试样后期强度,但掺量不宜过多。随造纸污泥灰掺量提高,水化产物中氢氧化钙和C—S—H凝胶生成量增大,氢氧化钙晶体由片状发育为板状,紧紧包裹于C—S—H凝胶层状结构中,造纸污泥灰中含有的文石型Ca CO3晶体具有较高的力学强度,可桥接于水化试样微观裂隙两侧,阻碍裂隙的扩展,进而提高胶凝体系的力学强度。 相似文献
724.
Babatunde Ogunfowora 《组织行为杂志》2013,34(8):1105-1123
The present study examined the consequences of a dispersion‐based conceptualization of unit‐level abusive supervision or abusive supervision variability. Abusive supervision variability was proposed to negatively affect a number of employee attitudes and behaviors through the mediating effects of interpersonal justice climate strength. The results revealed significant cross‐level effects such that abusive supervision variability was negatively related to individual perceptions of leader ethicality, organizational ethicality, leader satisfaction, and affective organizational commitment. These effects remained robust after controlling for individual‐level abusive supervision. Abusive supervision variability was also positively related to the frequency with which unit members as a whole engaged in counterproductive work behaviors. Last, the results revealed partial support for the mediating effects of interpersonal justice climate strength. In sum, the findings highlight the importance of examining abusive supervision at both the individual and unit levels of analyses. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
725.
Banibrata Das Tirthankar Ghosh Somnath Gangopadhyay 《International journal of occupational safety and ergonomics》2013,19(4):531-540
AbstractSixty female prawn seed collectors and 60 female control subjects from Sajenakhali and Sandeshkhali blocks of Sunderbans, West Bengal, India, were randomly selected to evaluate and compare musculoskeletal disorders and physiological stress. The control group was engaged in domestic work involving minimum hand-intensive activities. The modified Nordic musculoskeletal questionnaire and rapid entire body assessment were used. Most subjects suffered from discomfort in different body parts, especially in the lower back (98%), knees (88%), shoulders (75%), ankles (70%) and feet (67%). This study reveals that female prawn seed collectors suffer from significant physiological load and extreme physiological stress due to prolonged working hours in a standing posture and excessive work pressure. Consequently, all these factors affect female prawn seed collectors ‘ health and work performance. 相似文献
726.
Lanyards are still important and common components of personal systems protecting against falls from a height. Experience with dynamic strength tests of lanyards indicates that test methods based on EN and ISO standards do not make objective assessment possible. This paper presents the results of theoretical and laboratory investigations of the performance of adjustable lanyards during fall arrest. The obtained results indicate that methods of testing and assessment based on those standards demonstrate considerable shortcomings when applied to low elongation lanyards. The assumptions for improved requirements and test methods of lanyards made of e.g., steel wire and aramid ropes are also presented. 相似文献
727.
Alexander Ziv Ruwim Berkowicz Eugene Genikhovich Finn Palmgren Ekaterina Yakovleva 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):297-310
Since October 1998 two DOAS instruments were installed at the level of the first floor and at the top of a building located in St. Petersburg at Pestelya Street. The collected datacovers the time period of December 1998–March 2001, and include concentrations of benzene, toluene, NO and NO2, ozone and SO2. There is also an additional information about the traffic intensity and meteorological conditions. The results of the analysis of this data set, using the OSPM model, are presented here with the goal to understand the features of the air pollution dispersion in this street canyon and to analyse the information about the emission factors of the vehicles. In particular, the model results are used for the solution of the inverse problem of reconstructing the emission factors from measured concentrations. The results obtained indicate that most of the concentrations are well inside the Russian standards with the only exception of NO2 (mean and 98-th percentile are equal to 57.8 and 119.2 g m-3 for the street level). The same values for benzene are 18.5 and 62.6, respectively. Emission estimates show that there is a possibility that the NOx and benzene basic emission factors recommended by the Russian national guidelines could result in overestimating the traffic emissions. These considerations are supplemented with the model sensitivity tests carried out in connection with the problem of predictability of NO2 concentrations in the street canyon. Tests indicate that NO2 concentrations are not very sensitive to NOx emissions because of the usually low urban background ozone levels. 相似文献
728.
Rachana?Malviya Rubina?ChaudharyEmail author 《Journal of Material Cycles and Waste Management》2004,6(2):147-152
The sludge from a steel processing unit bearing zinc, lead, iron, and manganese was solidified with ordinary Portland cement. The waste was stabilized in the specimens with a waste/binder ratio range of 0.16–4.0. On the basis of the available leaching and unconfined compressive strength, the performance of the solidified/stabilized waste was compared for different numbers of curing days. It was found that curing up to 28 days resulted in a performance improvement, as shown by less leaching of heavy metals and the increased unconfined compressive strength of the specimen. The treatment effectiveness of the solidification/stabilization process was assessed for the metals Pb, Zn, Fe, and Mn, and was found to be 89%, 95%, 74%, and 90%, respectively, for an optimum ratio of 4.0 after 28 days of curing. 相似文献
729.
在安全生产系统中,生产事故是由于系统的控制力失控,而导致控制力失控是由于系统的创新力不足,即控制力与创新力的双重不足使安全生产事故成为必然。但由于安全生产系统中控制力与创新力二者的相互作用关系,两力在耦合演进中可以在更高层次上达到协调统一,从而有效避免生产事故。因而探讨两力协调统一的途径与方式对从根本上遏制生产事故,实现安全生产有重要的意义。 相似文献
730.
Utilisation of high volumes of limestone quarry wastes in concrete industry (self-compacting concrete case) 总被引:2,自引:0,他引:2
In limestone quarries, considerable amounts of limestone powders are being produced as by-products of stone crushers. High amounts of powders are being collected and utilisation of this by-product is a big problem from the aspects of disposal, environmental pollution and health hazards. In conventional concrete, the introduction of high volumes of limestone quarry dust to concrete mixes is limited due to its negative effects on water demand and strength of concrete. However, these fines can be efficiently utilised as viscosity enhancer particularly in special concrete (like self-compacting concrete—SCC) applications. Thus, the successful utilisation of this quarry dust in SCC could turn this material into a valuable resource.In this paper the usability of a quarry dust limestone powder in self-compacting paste and concrete applications was investigated. In the first part, the physical and mechanical properties of cement pastes incorporating quarry waste limestone powder (QLP) and a powder produced by direct grinding of limestone (PLP) were compared. In the second part, the performance of quarry waste limestone powder in SCC applications were tested and discussed. Results showed that, it is possible to successfully utilise high amounts of quarry waste limestone powder in producing normal-strength SCCs. Among its observed mechanical advantages, employment of quarry waste limestone powders improved the economical feasibility of SCC production. 相似文献