جستجوی مقالات مرتبط با کلیدواژه "فرآیند s" در نشریات گروه "عمران"

In the present paper, the uncertainty analysis for the activated sludge part in the wastewater treatment plant (WWTP) was done using stochastic differential equation (SDE) equations. Euler-Maruyama method was selected for the numerical solution of the It ̂o integral and the results were compared and analyzed with observational data.

The cement-based stabilization/solidification (S/S) method is widely used in modifying soils polluted by heavy metals (HMs), although it may face technical, economic, and environmental limitations. Therefore, the present work was designed to investigate the effectiveness of a type of geopolymer based on the steel slag (SGP) and its combination with microparticles of zeolite (SGPZ), compared to cement (as a traditional additive), in enhancing the stability of S/S products. In so doing, different percentages (0 to 250 mg/g-soil) of SGP, SGPZ, and sole cement were separately added to the S/S samples containing different concentrations of lead (including 5000, 10000, 20000 and 40000 mg/kg-soil). After adequate curing (up to 28 days), a set of macro and micro scale experiments were performed to assess the long-term performance of the amended soil samples using a laboratory accelerated aging procedure that simulated 25, 50, 75 and 100 years of exposure to the acid rain and wet and dry (W-D) cycles in the field. It was found that, while low amounts of cement (PC) would greatly reduce the initial bioavailability of pollution in the pore fluid of soil, increasing the contact time of the PC-treated specimens upon harsh conditions, especially in the presence of high level of Pb, would dramatically diminish the efficiency of the precipitation mechanism as well as the degree of encapsulation process which play a significant role in increasing the ability of S/S sample to release the toxic ions stabilized/solidified previously. At simulated 100 years, the toxicity characteristic leaching procedure leached Pb from the PC-treated sample with 250 mg/g-soil binder would exceed the permitted threshold of pollution leaching (≥ 5 mg/L) by 508%, indicating that meeting the S/S regulation limits requires a large consumption of cement. The study showed that, unlike treatment conditions with the same level of PC, the use of novel cement-free S/S binders (especially SGPZ) would significantly limit the negative influences of the environmental changes on HM remobilization risks. In addition, the mechanical characteristics of those series of samples were sometimes up to 1.4 times higher than that of the soil modified with cement alone. Based on the X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images, this enhancement can be mainly due to i) reduction in the adverse HM-binder interactions, ii) intensification in the level of hydration reactions, iii) formation of secondary complex hydrated phases (e.g., Hydrotalcite: Mg6Al2CO3(OH)16.4H2O), and iv) creation of a three-dimensional network of solidification in the system containing geopolymer, wrapping the matrix of S/S products against the structure disintegration upon contact to the aggressive environments. Therefore, under the destroying impacts of acid attack and W-D scenario, adding 25% SGPZ composite could pass the S/S regulation limits. In general, based on the obtained results, the use of geopolymer (especially containing zeolite) is suggested as an effective and environmentally friendly alternative for sustainable soil improvement, even with the high contents of HM ions. Following the USEPA and UKAE standards to achieve the safe S/S performance, the optimal dosage of GP binder was determined to be approximately 6 mg/g-soil per 1 g/kg of lead in the sample.

 The removal and treatment of sludge from municipal wastewater treatment plants is important due to environmental factors, so there is a significant incentive to discover and develop strategic plans to reduce excess sludge production in sewage treatment processes. Activated sludge system is used as the main biological process for municipal and industrial wastewater treatment and an excess sludge production rate in this process is between 15-100 liters per kilogram of removed BOD5. One of The usages an anaerobic reactor in the activated sludge system known as the Cannibal process that is one of the conventional methods used to reduce the sludge production rate at the sewage treatment line, which has low operating costs and relative simplicity to process design. The system's overall reducing efficiency is generally up to 50%. The purpose of this process is less production of sludge and also improvement of wastewater quality. In order to achieve reduction in excess sludge production, different mechanisms are considered which include microbial predation, uncoupling metabolism, endogenous metabolism and lysis-cryptic growth. The microbial predation mechanism is one of the important mechanisms in the cannibal process that is a suitable choice for reduction of excess sludge because of its low strategic cost and environmental compatibility. The objective of this research is the applicability of Quorum quenching (QQ) phenomenon in a conventional Cannibal process for enhancing the microbial predation mechanism to improve the efficiency of reducing sludge and other effective sludge parameters. Quorum sensing system is a new method of managing social behavior of microbial Population. The decomposition of Acyl Homosserine Lactones (AHL) is the most usable and practical way for creating disturbance in Quorum sensing system. For increasing the free bacteria population, Quorum quenching agent is used in the aerobic tank. These enhance microbial predation and show decrease in Extracellular Polymeric Substances (EPS). So far many bacteria with QQ feature are reported in biological wastewater treatment reactors. The basis of this project was designed in two laboratory phases and the reactors were operated with synthetic wastewater. In the first phase, the cannibal process was used in the form of a laboratory reactor, and in the second phase, by installing a separate aeration reactor and adding the Rhodococcus sp.BH4 bacteria, a quorum quenching bacteria, in a polymeric structure of alginate and introduced as QQ beads. The modified Cannibal process was designed. Microbial predation mechanism is one the methods that increase population of eukaryotic predators by changing the microbial structure of activated sludge system; by this method, efficiency of reduction of excess sludge production is increased. The results showed that the presence of QQ grains led to an increase in the number of eukaryotic species. The yield coefficient (Yobs) in the modified Cannibal and the control Cannibal was 0.389 and 0.092, respectively, with a significant decrease of 77%. Also, the results of EPS, which indicates the proper functioning of this system, has been analyzed and investigated. The applied QQ primary treatment enhances the Microbial predation mechanism in Cannibal system, significantly improve the efficiency of this system, and biological excess sludge notably is decreased.

To eliminate the defects of merely systematic materialistic attitudes, one can refer to the divine systematic thinking and benefit from the transcendental teachings of Islam. Non-linear thinking and dynamic view of phenomena and consequences is the neglected point of managers' decisions in businesses and commercial and non-commercial organizations. The employees of the organization always seek to know the results of their performance and are interested in monitoring their performance changes. In all the organizations of the world, managers and organizational leaders seek to improve and improve the performance of their organizations. Organizational performance is an indicator that measures how an organization or institution achieves its goals. With the aim of investigating and evaluating organizational performance through systemic thinking, this article reviews the viewpoints of managerial and organizational performance evaluation criteria, indicators and types of performance evaluation models. The results showed that the design and selection of performance evaluation indicators is one of the basic phases in the design of the organizational performance management system. In the performance evaluation process, the organization excellence model (EFQM) is a self-evaluation process and a comprehensive systematic method to identify the organization's strengths and improvement points. As a result, the organization compares itself with the best in the world or national class.

A critical research area overlooked in previous studies on nano-silica material is the understanding of how its physical characteristics influence its final behavior as a composite when added to the asphalt binder. This study aimed to understand the feasibility of modifying the nanosilica with asphalt binder based on the asphalt binder characteristics. 60/70 penetration grade asphalt cement was prepared by adding (2%, 4% and 6%) of nanosilica by weight of asphalt. Properties of nanosilica material and asphalt cement were first examined. To prepare the modified asphalt binder was heated at 140C, blended by mechanical mixer at a speed of 2000 rpm for different mixing durations (30 to 60) minute. The modified asphalt binder was examined for rheological properties including penetration grade, softening point temperature, penetration index, Brookfield rotational viscosity and ductility test. Results shows that the modified asphalt binder stiffness increases based on rheological properties and sensitivity of temperature decreases with increasing nanosilica percentage. A 4 % nano silica by asphalt weight enhanced the conventional properties of the modified asphalt binder and became proper in hot weather conditions. While ductility of modified asphalt decreases with increasing nano silica percentage, due to stiffness and agglomeration increased. Finally, longer mixing time to more than 60 min had an adverse effect on the ductility property and lead to agglomeration of nanosilica modified asphalt binder.

One of the main causes of damage to dams, especially earth dams is the overtopping which may cause huge human losses and financial damages. Fuse plug is used as a safety valve to protect dams against catastrophic damages of overtopping. The increasing outbreak of floods and their huge and sometimes irrecoverable damages has incentivized dam experts and designers for more studies on the most effective and economical spillway construction. The attempt is towards letting higher amounts of water run through spillways. One approach is using an auxiliary spillway beside the main spillway. Fuse plug can be used as an economical auxiliary or emergency spillway. Fuse plug structure consist of embankment body and pilot channel. Fuse plugs are designed with the same details and ingredients of many earth and rockfill dams. In terms of the material of their body, fuse plugs are categorized as either homogeneous or non-homogeneous. As a result of the embankment erosion, the waterway opens up. When the flood is over, the embankment is reconstructed. The fuse plug operation is totally automatic and does not require human intervention. At other times, fuse plug should be stable and have reliability coefficients equal to those of earth dams. In this experimental research, the effect of the body grain size of embankment fuse plug on the failure and washout mechanism of non-cohesive homogeneous fuse plug is evaluated. The water level upstream of fuse plug is kept constant throughout the overtopping and failure processes, the tests thereby simulating the failure of embankment fuse plug impounding a very large upstream reservoir. The failure trend and mechanism, rate of embankment sediment washout and the output hydrograph of overtopping are addressed. The breach shape and failure mechanism can be used as a guide to interpret the extent of grain size effect and failure progress. The mechanisms of embankment breach due to overtopping can be categorized into 2D and 3D processes. 3D mechanism consists of both lateral and vertical erosions, whereas 2D mechanism only consists of vertical erosion. In this research, both types of erosions were observed. Initially 3D mechanism is observed and breach expansion continued until the breach reached the flume walls. Then after the 2D mechanism failure was observed. Also the equation obtained for describing non-dimensional embankment crest in 2D process by non-dimensional time and non-dimensional grain size. The mean rate of washout in test No.2 is the highest and an analysis similar to the mean rate of washout materials can be generalized to the washout period, which given the uniformity of the total volume of materials, is a rational generalization. The important point in the optimal performance of the fuse plug during the time of destruction is the volume of more outlet water in a shorter time period at the level desired by the designer. The material used in the embankment body with d* equal to 0.004, taking into account the results obtained, including the minimum water level behind the structure, reducing drained water, preventing structural instability due to the piping and the higher total erosion rate is an appropriate choice for building an embankment plug fuse in the range of test parameters.

Ingredients in agricultural pesticides are a group of chemicals and synthetics that are widely used in the industry. The constant entry of these substances into water resources produces very high levels of pollution, which poses a threat to aquatic environments and their organisms. Among the pesticides used in agriculture are organophosphorus, carbamate and pyrithioide pesticides. Organophosphorus and carbamates have the highest levels of consumption to deal with plant pests. In this study, the photocatalyst was synthesized by ball mills method. In this method, oxide and iron oxide nanoparticles were rotated in half steel compartment (40.5 g of oxide and 80 g of iron oxide) for 12 hours in a high-energy satellite mill at 300 rpm. The weight ratio of the catalyst to 10 mm spheres is 1:20 and for each 15 min rotation, 5 min rest and a total of 16 h cyclical rotation was performed in the device to complete the nanocomposite synthesis process. Heat treatment was carried out for 1 hour by a muffle furnace at 700 ° C. Also, this nanocomposite were characterized with the analysis of XRD, XRF, DRS and FTIR. The XRD analysis showed the hexagonal structure of nanocomposite with using of Debay-Scherer relationship, the crystals size of ZnO/α-Fe2O3 nanocomposite was calculated about 10.66 nm. SEM images showed the Fe2O3 nanoparticle Placement between ZnO nanoparticle. Result of DRS revealed that band gaps of the ZnO and Balmiled iron oxide and heated was 1.878 eV. By FTIR analysis, peaks of Zn-O and Fe-O were observed in the nanocomposite. According to EDX analysis for the weight values of Zn and Fe and O of ZnO/α-Fe2O3 nanocomposite was 5.30% and 55.8%. According to XRF analysis, the weight values of Zn and Fe in ZnO/α-Fe2O3 nanocomposites were 77.33% and 61.13%, respectively. The photocatalytic activity of the synthesized ZnO/α-Fe2O3 nanocomposite under UV irradiation was analyzed by two 8 watts UVC lamps for mineralization of organic carbamate pollutants from agricultural wastewater. In this design ZnO/α-Fe2O3 nanocomposite concentration, pH and radiation time were considered as effective quantitative variables and the type of catalyst consumed as effective qualitative variables. Reaction rate reached best at 0.0043 min-1 in the best conditions, including modified oxide and catalyst concentration of 1 gr/l and two 8W UV lamps and pH = 8 for 3 hours.

The purpose of this study was to compare the performance of Fe2+ activated persulfate and electro-persulfate process in Acid Blue 25 removal from aqueous solution. For this reason, the effects of different parameters including pH, dye, sodium persulfate and ferrous sulfate concentrations were investigated. The removal efficiency of 92% at the time of 60 min was obtained at pH= 3, dye concentration= 50 mg/L, sodium persulfate concentration= 500 mg/L and Fe (II) sulfate concentration= 100 mg/L for Fe2+ activated persulfate system and the removal efficiency of 95% at pH= 5, dye concentration = 200 mg/L, sodium persulfate concentration = 500 mg/L and ferrous sulfate concentration = 100 mg/L for electro-persulfate system by means of graphite materials as the neutral electrodes. COD removal efficiency in Fe2+ activated persulfate and electro-persulfate in the mentioned conditions were 90% and 89% in 180 minutes, respectively. Moreover, the result of process kinetics showed that using electrochemical process improved the reaction velocity from 0.0016 to 0.0487 mg/L/min. The comparison between these two-process showed that using electrochemical process improved dye removal efficiency by 4 times.

Industrial and economic development along with changes in lifestyle over recent decades in most countries has resulted in considerable growth of different waste. Since biodegradable organic materials constitute approximately 60% of the total municipal solid waste in developing countries, leachate treatment is considered as a big concern for solid waste management in these areas. Application of biological processes is one of common method in leachate treatment. However, due to presence of refractory pollutants, biological process alone cannot treat leachate on its own. In order to enhance the quality of leachate to the discharge standards, post treatment of biologically treated leachate is essential. One appropriate solution for complementary treatment of leachate and removal of refractory materials is the application of advanced oxidation rocesses. The Fenton process is one of homogenous advanced oxidation processes has been applied for leachate treatment. However, this method is time-consuming and expensive. In order to improve the performance and reagent utilization efficiency, in this paper microwave enhanced Fenton process was utilized for post-treatment of composting leachate. Batch laboratory scaled experiments were employed on effluent of leachate treatment plant of a composting factory in Iran. Initial experiments were conducted and then the effects of variables were determined separately by one factor at a time (OFAT) method. The effects of factors such as pH, ratio of concentration of H2O2 to initial COD, ratio of concentration of H2O2 to Fe2+, and Microwave irradiation power on the microwave enhanced Fenton process efficiency were investigated. According to obtained results the maximum removal efficiency of Microwave enhanced Fenton process was obtained at pH=3, ratio of H2O2 concentration to initial COD equals to 3.75, ratio of H2O2 concentration to Fe2+ concentration of 3, and Microwave irradiation power of 170W. The experimental results indicated that, under this optimum conditions, the removal of COD, total nitrogen, color, and turbidity were 72%, 70%, 75% and 88% respectively. Results of this research addresses that, applied process is unable to reduce organic load of the leachate in a way that it could be discharge in receiving environment. However, the ratio of BOD5/COD was elevated from 0.01 to 0.25, representing substantial improvement in biodegradability. By so doing, a common biological process such as activated sludge could be hopefully utilized to reduce remaining organic load to the limits set by the standard.

Nowadays, the evaluation of reliability and availability is one of the most important criteria in all engineering sciences .Due to the increasing of dependency of the life into the electrical energy, the availability of power system is very important for consumers. To achieve this issue, each of the main components of the power system must have adequate reliability. In this paper, reliability evaluation of the pumped storage plants using Markov process is carried out. For this purpose, at first an overview of the structure and the usage of the pumped storage plants is presented. Then, the main concepts of the Markov process model are reviewed and the appropriate model for reliability evaluation of a pumped storage plant is presented. Using the presented model and according to existing equipment, various indicators of reliability and also the possibilities of failure mode, full and half capacity of the plant are reported and sensitivity analysis is carried out to evaluate the effect of repair and failure rates of equipments on reliability of the plant.

Reliability analysis of steel structures subject to seawater corrosion is of considerable interest for coastal and offshore marine steel structures. These are often very expensive and have high consequential costs and implications should failure occur. Since corrosion of steel structures causes deterioration of structural strength, usually gradually with time, safety assessment is of considerable importance for new structures (those in the design stage) and also for those which are already in operation.
Marine corrosion is a complex phenomenon and subject to various influencing factors each of which has its own inherent uncertainty. In any safety assessment, in principle, the uncertainty of each factor should be studied and taken into account. Since such an action is too difficult, in practice some test programs are normally conducted and all uncertainties caused by different factors are assumed to be included in the relevant corrosion measurements.
In addition, in any corrosion reliability analysis for steel structures exposed to seawater, two different models must be taken into consideration: (1) A physical model indicating general corrosion behaviour as a function of exposure time and (2) A stochastic model describing probabilistic treatment of uncertainties observed in real corrosion data. The first has been traditionally treated by invoking a simple power law and in particular a linear relationship. However, using realistic long-term data, validity of such a model has recently been challenged. The second model (i.e. probabilistic modelling of corrosion process) has been dealt with in literature in different approaches, including either taking the corrosion annual rate as a random variable or proposing a stochastic process such as Gamma process. This is usually proposed as a general structural deterioration process. The second approach provides, doubtlessly, better treatment of corrosion uncertainties; however it can be shown unfortunately that the Gamma process is unable to reflect the corrosion uncertainties in some circumstances.
In this paper, two sets of corrosion data collected in different seawaters around the world with different temperatures are used. This requires processing of data in such a way that the data sets remain consistent with each other and that outcome is data that can be considered as belonging to one statistical population. Herein, first, a simple algorithm is proposed to transform the whole data to one common temperature. Second, a novel Markov-chain based model is developed which meets long term second-order corrosion statistics (i.e. means and standard deviations of corrosion losses). It is based on a corrosion model that previously has been calibrated extensively to field observations of corrosion and to literature-reported realistic data. Although actual long-term field observations of marine corrosion of steel are scarce, it is shown that particularly for the standard deviation the new model is well capable to be consistent with the long-term data.
It is noted that herein, only the corrosion data collected in marine immersion zones are considered (i.e. those taken in splash zones and atmospheric zones are not considered). Further, only general corrosion (i.e. not pitting corrosion) is accounted for herein. These issues, obviously, have to be addressed separately.

Increasing the maritime transportation market and using the container have led the large volume of containers to the seaports. Considering the long time presence of containers in the country's seaports and the traditional structure of container transportation, not only can cause high fuel consumption but also increase the diverse environmental pollution, traffic congestion and road accidents. Therefore constructing the dry ports or internal logistics ports is one way that has successful experiences in other countries. The idea of dry port's presence in the special distance from the seaports has reduced many of the problems have been created for the seaports. However, the optimum location of dry ports has to be determined, like all service centers, and correct extension of them has valuable achievements. The main objective of this study is locating the site for construction of dry ports in the country. On the other hand locating of them is eclipsed of different and sometimes contradictory quantitative and qualitative criteria. Due to the Analysis Hierarchical Process is one of the most comprehensive systems for multiple criteria decision making techniques and this method has enough ability to consider various quantitative and qualitative criteria, so in this study it was used to determine the weights of criteria and alternatives and after the ranking of options, the results were compared. In this study, field research and library resources has utilized for determining of effective measures in the dry port's locating. Then these factors were divided to benefits and cost factors and weight of them was determined with using of a questionnaire and binary comparison. Finally, the incremental benefit/cost analysis was used for the ranking of alternatives in order to construct the dry ports.

The growing rate in solid wastes production leads to considerable generation of leachate. Leachate is defined as the aqueous effluent generated as a consequence of precipitation percolation through wastes، biochemical processes in wastes body and the inherent water content of wastes themselves. Since the leachate contains significant amount of organic and inorganic compounds، it is not allowed to be directly discharge to the environment. Conventional treatment techniques to remove organic matters from leachate include physical، chemical and biological processes. Most of these techniques are non-destructive and do not solve the environmental problems because the wastes are simply transferred from water to another phase creating secondary wastes pollution. Biological method was regarded as the most efficient and cheapest process to eliminate organic materials from leachate. However، biological process cannot usually remove refractory substances. Therefore، the effluent values of the organic content do not meet the standards of the treated wastewater with respect to persistent contaminants. Due to limited biodegradability، the treatment of leachate، apart from biological methods necessitates the application of other methods، which complement and support the main process. Advanced oxidation process has been intensively studied in the past decade to improve the removal of these large refractory organic molecules or to transform them into more easily biodegradable substances. Among them photocatalytic process is one of the appropriate methods for final treatment of these kinds of waste. In this study، application of photocatalytic process via UV light and TiO2 Nano particles immobilized on concrete surface in post-treatment of composting leachate was investigated. This investigation was conducted in laboratory scale and batch mode. A biological pre-treated leachates sample which contains some macromolecular organic substances that were resistant to biological degradation were collected from the effluent of leachate treatment facility، of Gorgan composting plant (Golestan، Iran). UV-C lamps with different power in the range of 8-107 W at a constant distance of 10 cm from the surface of the leachate were used as the source of irradiation. Pervious concrete was constructed using LECA lightweight aggregates with the dimension of 30*10*10 cm. Immobilization of TiO2 on concrete surface was done by using concrete sealer. In order to investigate the effect of each parameter individually، some experiments were carried out. The results showed that the presence of nanoparticles and UV radiation alone did not significantly affect on the COD removal. According to the conducted experiments the maximum COD removal of 62% was achieved after 20 hr radiation with 7. 5 mW. Cm-2 intensity in pH value of 5 and in presence of 60 g. m-2 of TiO2 coated on concrete. According to Iranian environmental standards and with regard to organic loading of leachate، removal efficiency of this process was in such a way that it could be directly discharged into the environment.

In risk allocation process, it is not correct to pass the whole responsibility of some risks to the contractor. The reason is that some defensive strategies such as lowering the work quality and lodging claim and litigation may be implemented by the contractor that may increase the project cost and duration. It is therefore necessary to share the responsibility of these risks between contracting partiesandin the other words to perform the risk allocation process quantitatively. In the negotiation process performing to determine the percentage of risk allocated to each of the contracting parties, there exists a willing to cooperate and reach an agreement in spite of the existed conflicts in the revenues of these parties. In this research, the game theory that is the study of mathematical models of conflict and cooperation between intelligent rational decision-makers is used for quantitative risk allocation. The proposed model presents a powerful tool that satisfies desirable criteria such as efficiency and fairness and the equitable percentage of risk allocation is determined. To evaluate the capabilities and performance of the proposed model, it is implemented in sample project and the risk allocation percentage between the client and contractor is determined for one of the identified risks.