Estimation of maximum scour depths at upstream of front and rear piers for two in-line circular columns

Previous investigations indicate that scour around bridge piers is one of the most important factors for the failure of waterway bridges. Hence, it is essential to determine the accurate scour depth around the bridge piers. Most of the previous studies were based on scour around a single pier; however, in practice, new bridges are usually wide and then piers comprise two circular piers aligned in the flow direction that together support the loading of the structure. In this study, the effect on maximum scour depth of the spacing between two piers aligned in the flow direction was investigated experimentally under clear water scour conditions. The results show that the maximum scour depth at upstream of the front pier occurs when the spacing between the two piers is 2.5 times the diameter of the pier. Two semi empirical equations have been developed to predict the maximum scour depth at upstream of both front and rear piers as a function of the spacing between the piers, in terms of a pier-spacing factor. If the new equations for the pier-spacing factor are used with some of the existing equations for scour at a single pier, the predicted scouring depths are in good agreement with observed results. The S/M equation exhibited the best performance among the various equations tested and was recommended for use in prediction of the equilibrium scour depth. The findings of this study can be used to facilitate the positioning of piers when scouring is a design concern.     

Effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria: Soot-ceria contact and interfacial oxygen evolution

Ceria is widely used as a catalyst for soot combustion, but effects of Zr substitution on the reaction mechanism is ambiguous. The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria. The nanostructured CeO₂, Ce_0.92Zr_0.08O₂, and Ce_0.84Zr_0.16O₂ composed of 5–6 nm crystallites display T_m-CO2 (the temperature at maximum CO₂ yield) at 383, 355, and 375°C under 10 vol.% O₂/N₂, respectively. The size of agglomerate decreases from 165.5 to 51.9–57.3 nm, which is beneficial for the soot-ceria contact. Moreover, Zr increases the amount of surface oxygen vacancies, generating more active oxygen (O₂^? and O^?) for soot oxidation. Thus, the activities of Ce_0.92Zr_0.08O₂ and Ce_0.84Zr_0.16O₂ in soot combustion are better than that of CeO₂. Although oxygen vacancies promote the migration of lattice O^2?, the enriched surface Zr also inhibits the mobility of lattice O^2?. Therefore, the T_m-CO2 of Ce_0.84Zr_0.16O₂ is higher than that of Ce_0.92Zr_0.08O₂. Based on reaction kinetic study, soot in direct contact with ceria preferentially decomposes with low activation energy, while the oxidation of isolated soot occurs through diffusion with high activation energy. The obtained findings provide new understanding on the soot combustion over nanoceria.     

Control of TAME reactive distillation using Non-Dominated Sorting Genetic Algorithm-II

The control system performs poor in characteristics and even it becomes unstable, if improper values of the controller tuning constants are used. So it becomes necessary to tune the controller parameters to achieve good control performance with the proper choice of tuning constants. Many control problems involve simultaneous optimization of multiple variables that competing with each other. In this paper, the Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) has been successfully applied to optimization of dynamic state of t-amyl-methyl-ether (TAME) reactive distillation process. This paper presents the tuning of Proportional-Integral-Derivative (PID) controllers by minimizing of two objective functions (overshoot and Integral of Absolute Error (IAE)) through the NSGA-II. Results show that genetic algorithm is more suitable method for optimal control of the TAME reactive distillation columns than traditional methods such as Tyreus-Luyben.     

Spatial and temporal variability of fluoride concentrations in groundwater resources of Larestan and Gerash regions in Iran from 2003 to 2010

Environmental Geochemistry and Health - There is discrepancy about intervals of fluoride monitoring in groundwater resources by Iranian authorities. Spatial and temporal variability of fluoride in...     

Major Health Risk Factors in Iranian Hand-Woven Carpet Industry

This paper reviews the role and importance of small-scale industries together with the issue of occupational health problems and their causes in Iranian hand-woven carpet industry as a typical informal small-scale industry in an industrially developing country. The objective ofthis paper is to review health risk factors and related occupational health and ergonomic problems in the carpet industry. Since the overwhelming majority of weavers’ health problems originate from ergonomic risk factors, it is concluded that any improvement program in this industry should focus on ergonomic aspects. To assess ergonomic conditions in weaving workshops, a checklist has been developed and an ergonomics index indicating the ergonomic conditions of the workshop has been proposed. To test and verify the checklist, 50 weaving workshops were visited and their ergonomic conditions were assessed. Based on the results some modifications were made and the checklist was shown to be an effective tool.     

Postural Loading Assessment in Assembly Workers of an Iranian Telecommunication Manufacturing Company

Background. Changes in industries and work practices have coincided with work-related musculoskeletal disorders (MSDs). This study was conducted to determine the prevalence of MSDs and to assess postural loading in assembly workers of an Iranian telecommunication manufacturing company. Methods. Data were collected from 193 randomly selected workers in 4 units of the company. The Nordic musculoskeletal disorders questionnaire and the UBC ergonomic checklist were used as data collection tools. Loading on the upper body assessment (LUBA) was used to assess postural loading. Results. Lower back symptoms were the most prevalent problems among the workers (67.9%). LUBA showed that most assembly workers (94.3%) had experienced considerable and high postural loading (postural load index, PLI > 5). Regression analyses revealed that lighting, rotation, contact stress, repetition, gender and age were factors associated with symptoms. Conclusion. Work-related MSDs occurred at a high rate among workers. Postural loading requires consideration. Any ergonomic intervention should focus on eliminating ergonomic factors associated with symptoms.     

Multiple dimensions of work-related risk factors and their relationship to work ability among industrial workers in Iran

Objectives. The present study was designed to investigate the simultaneous effects of physical, psychosocial and other work-related risk factors on the work ability index (WAI) score among industrial workers. Methods. This study used a cross-sectional design with a questionnaire survey. A total of 280 workers were included in the study. Data were collected using three questionnaires including the Persian version of the WAI, the Persian version of the job content questionnaire and an author-developed measure (to assess work-related factors, health-related factors and socio-demographic characteristics). Results. The majority of the participants were young, but they had poor WAI scores (mean 37.3?±?6.4) and 44.3% of them had poor or moderate work ability. Occupational accidents and injuries were found to be the strongest predictors of WAI scores. Additionally, there was a strong association between WAI scores and supervisor support, skill discretion, occupational training, sleep quality, work nature and educational level. Conclusions. Intervention programs should focus on improving supervisor support, sleep quality, job skills and knowledge and on decreasing physical and mental work demands. Additionally, implementing a comprehensive occupational health and ergonomics program for controlling and reducing hazardous working environments and occupational injury rates should be considered.     

Three-dimensional analysis of coherent turbulent flow structure around a single circular bridge pier

The coherent turbulent flow around a single circular bridge pier and its effects on the bed scouring pattern is investigated in this study. The coherent turbulent flow and associated shear stresses play a major role in sediment entrainment from the bed particularly around a bridge pier where complex vortex structures exist. The conventional two-dimensional quadrant analysis of the bursting process is unable to define sediment entrainment, particularly where fully three-dimensional flow structures exist. In this paper, three-dimensional octant analysis was used to improve understanding of the role of bursting events in the process of particle entrainment. In this study, the three-dimensional velocity of flow was measured at 102 points near the bed of an open channel using an Acoustic Doppler Velocity meter (Micro-ADV). The pattern of bed scouring was measured during the experiment. The velocity data were analysed using the Markov process to investigate the sequential occurrence of bursting events and to determine the transition probability of the bursting events. The results showed that external sweep and internal ejection events were an effective mechanism for sediment entrainment around a single circular bridge pier. The results are useful in understanding scour patterns around bridge piers.     

Evaluation of potential toxic effects of occupational inhalation exposure to licorice root dust

Licorice, a plant indigenous to southern Europe, the Middle East, and northern China, exhibits several pharmacological properties, including estrogenic, anti-tumoral, anti-inflammatory, anti-allergenic, and anti-tussive activities. Prolonged use of licorice is known to produce headaches, hypertension, cardiac arrhythmias, edema, lethargy, dyspnea, sodium retention and loss of potassium in humans. However, to date, the potential adverse health effects due to occupational inhalation exposure of licorice root dust remains unknown. This study was, therefore, undertaken to address this issue. In this cross-sectional study, individuals (30 workers) occupationally exposed to licorice root dust at a licorice producing plant in Shiraz, Iran were recruited. Similarly, 30 healthy male unexposed employees at a telecommunications industry, with identical demographic and socioeconomic status, without any past or current exposure to licorice dust or habitual ingestion of this compound, served as the referent group. Systolic and diastolic blood pressures were measured. Further, individuals underwent electrocardiography, clinical examination and blood chemistry tests. To assess the extent to which subjects were exposed to licorice root dust, atmospheric concentrations of this compound were also measured in the plant. There were no differences in age, weight, height and duration of exposure to licorice dust or length of employment between exposed and referent groups. Atmospheric measurement of licorice dust showed that concentration exceeded the permissible limit of 5 mg m^?3. Systolic and diastolic blood pressures of exposed subjects were significantly higher than those of the referent group. Similarly, blood analysis revealed that serum concentrations of potassium and platelet counts were significantly lower in exposed subjects than in referent individuals. Questionnaire data demonstrated that symptoms such as headaches, lethargy, and vertigo were more common in exposed subjects. No abnormal changes were noted in the electrocardiographs of exposed or referent subjects. Our findings provide evidence that inhalation exposure to high concentrations of licorice dust is associated with an increased prevalence of headache, lethargy, and vertigo, as well as hypertension and hypokalemia. None of these changes resulted in increased morbidity and mortality in exposed workers.     

Hazardous waste management in educational and research centers: a case study

The hazardous waste management (HWM) practice at Tehran University of Medical Sciences Central Campus, Iran, was investigated in this study. Four schools were selected and the required information such as type and amount of wastes, temporary storage methods, waste discharge frequency, and final waste disposal methods using sampling, questionnaires, interviews with laboratory staff, and reference to available documents were gathered. The quantity of hazardous waste generation per year excluding the uncontrolled wastewater was found to be 2.072 tons per year. The obtained results show that wastes having features of being infectious, toxic, ignitable, carcinogenic, corrosive, and reactive were present at 32%, 28%, 16%, 14%, 8%, and 2%, respectively. In the central campus, hazardous solid wastes managed with household solid wastes and hazardous liquid waste were discharged into the sinks without any kind of control; improper HWM practices are evident from the point of waste production to final disposal.