جستجوی مقالات مرتبط با کلیدواژه « s process » در نشریات گروه « عمران »

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.

Every country with any level of development seeks further development. In this article, by presenting an innovative method derived from the concept of work and its relationship with power and the direction of its application, a new approach to development indicators and especially the Inclusive Development Index (IDI) is proposed. This method is a development on IDI that takes economic, social and environmental aspects into account.For this work, countries were grouped based on their IDI pattern and analyzed to quantify the compatibility of national resources used with planned development strategies. The results obtained for each country provide an insight into whether the use of additional resources can further improve the development index or the need to revise or change the planned strategies before taking any further action.Subsequently, based on the water and green growth model that is proposed for institutional evaluation and analysis of policy instruments, the projects of Iran's water sector were evaluated. This analysis was done based on questionnaires answered by university and industry experts. The final result reveals the need to review the strategies and programs of the country's water sector.

Nowadays, the close competition of airline companies in attracting passengers has made it very important for planners and policymakers in this field to investigate the psychological issues and the differences in the passengers' views. Different airline companies seek to examine the ideals and values of passengers in order to identify their strengths and weaknesses in order to maintain their position in the competitive market or promote it with correct and accurate planning. In this study, various factors affecting satisfaction from the passengers' point of view are examined using survey data and logistic regression modeling. The factors examined in this study include characteristics such as age and gender, loyalty to the airline, and the level of satisfaction with the quality of various services such as food and internet services, baggage handling services, and online ticket booking. In addition, the effect of variables related to each flight, such as distance and delays, are also investigated on passenger satisfaction. The modeling results of this research show the importance and significance of the variables of type of travel (personal or business), type of passenger (loyal or not loyal to the company), class of travel (Eco or Eco Plus or business), the level of satisfaction with baggage handling and the level of satisfaction with the boarding process. This study has shown the high sensitivity of passengers to the process of getting on the plane and also to baggage handling.

 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.

Currently the only unit for the production of phosphoric acid by wet chemical method in the country is Arya Phosphoric Jonub Company with the production capacity of 381 thousand tons per year of phosphoric acid solution with a concentration of 50%. Due to the widespread need for this acid in the country, the need to design and build a new unit for the production of phosphoric acid is strongly felt. Designing and constructing industries require knowing the theoretical foundations and having practical and experimental perspectives in accordance with the prevailing economic and cultural conditions and the existing technical knowledge of society, in order to achieve production goals. Technical study and optimization of phosphoric acid production conditions by dihydrate method is done in line with these goals. The discussion of process optimization is always fraught with many difficulties and complexities. One of the most important challenges ahead is access to process information such as purity of raw materials, temperature limits, pressure and flows rate, limitation of the use of equations and laws of transfer phenomena. In this project, we have tried to design and simulate a phosphoric acid production unit according to the needs of the country and the soil used in this unit, using the powerful Aspen Plus software. Various experiments were performed on the sample received from the National Iranian Copper Industries Company and based on the results of these analyses, the process was designed and simulated. Finally, the simulation results were presented.

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.

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.

The purpose of the present study was to evaluate and compare the impact of "sanctions" and "mismanagement" on the implementation process of the National Petroleum Zones Company's facilities. The present study was applied in terms of deductive-inductive method and in terms of purpose. The statistical population includes all managers, deputies and experts of the National Iranian Oil Company (NIOC), including 200 people. The sample size was 131 using Cochran formula. The research instrument was a researcher-made questionnaire. AHP technique was used in this study. Also by paired comparisons and AHP method using Expert Choice software. For this purpose, using the hierarchical approach, the hierarchical tree was first formed using this method, then the alternatives were evaluated according to the criteria and then the factors based on the objective function were investigated and then using The hierarchical approach was first to form a hierarchy tree, and then to examine the options examined to evaluate and compare the impact of sanctions and mismanagement on the implementation process of the National South Oil Company's facility design projects, and to manage managers' knowledge, human resources management, and trans-organizational factors, respectively. , Ethical Behavior of Managers, Science and Ph Innovation, finance and banking, economics, logistics and commodities had a major impact on the implementation process of the National South Oil Company's facilities. Further mismanagement of the sanctions also affects the process of implementation of the National Petroleum Company's facilities.

In the past two decades, using different methods and techniques for the implementation and management of construction projects has increased dramatically. Not only has the success rate of projects had appropriate progress, but also we have faced with schedule delays, increased costs, poor quality and increased number of claims and litigation. Nowadays major concern of many project managers is to complete the project on time and on budget in complex environment. Maybe we find out some environmental factors that impact on it, while the project managers do not consider that in critical situation. This research introduces the complex environment of construction projects and explains different types of complexity in order to achieve those factors. The main purpose of this paper is to identify complexity factors of project time management within the PMBOK process. In addition to proving complex and chaotic environment of project time management, we introduce these factors. Effective Parameters will be recognized and we should consider those in project planning and control, those are ignored in most of the projects and cause difficulty. Clarifying the problem and significant impacts on the implementation process will be represented the appropriate approach on project time management.

This study investigates the capability of cement-SiO2 nanoparticles (CNS) mixture to the promotion of stabilization/solidification (S/S) process of heavy metal (HM) contaminated soils. For this purpose, artificially contaminated soil samples were first prepared by mixing kaolinite with nickel (Ni) and then a set of tests were performed to assess the effectiveness of the CNS treatment. The results indicate that the addition of cement markedly increases the HM retention of soil; however, the TCLP tests show that leaching of cement treated samples leads to return a part of pollutants to soil pore fluid. The cement and Ni interaction has a destructive impact on particles solidification which adversely affects the strength development and compressibility of the cement-stabilized specimens. At same condition, the CNS blend is more efficient in immobilizing Ni and modifying the soil engineering properties as compared to sole cement. Based on the physicochemical, XRD and SEM tests, the better performance of CNS agent is mainly associated with the more and faster growth of cement compounds, reducing the adverse effect of heavy metal precipitation on the hydration reactions and increasing the particle density. The study concluded that with the consideration of EPA criteria, an optimum cement content of 0.5 wt% per one cmol/kg.soil of HM within 28 days of curing can successfully remediate the Ni contaminated soils. The incorporation of SiO2 nanoparticles into the binder system improves the microstructure and geomechanical performance of stabilized materials and causes a significant reduction in the cement consumption (up to 35%) and time of curing (up to 3 times)

Discharging wastewater effluent to surface water or groundwater is so dangerous for environment, while it includes nutrient. As the phosphorus and nitrogen combinations in the aquatic environments have harmful impacts (mainly the poisonousness of ammonia, overgrowth of aquatic plants, groundwater pollute to nitrate and diseases caused by drinking the polluted water, and also eutrophication, resulting in frequent outbreaks of algal blooms and threatening the reliable supply of drinking water resources), some limitations were imposed on the consistency of these combinations in the entry waste. So nowadays removal of these combinations must be considered in designing of the treatment plants and also systems designed for treating the municipal wastewater must be able to remove nitrogen and phosphorus combinations to reach the standard limit. Therefore, in order to good performance of the aerobic-anaerobic A2/O method, it is proposed in this research and a study in advanced treatment of municipal wastewater using the A2/O method to remove nitrogen and phosphorus in the pilot scale in Ekbatan WWTP has been done.
In this research, firstly the principals of biological removal of nitrogen and phosphorus, and secondly the basis of designing biological treatment plants have been investigated. Then for laboratorial studies, an A2/O pilot has been made. This pilot consists of anaerobic, anoxic and aeration tanks and also sedimentation tank. The volume of these 4 tanks are 40, 60, 170 and 120 L, respectively. In order to simulate the real condition, this pilot has been set up in Ekbatan plant and the experiments were done to observe the effect of hydraulic residence time on nitrate, ammonia and phosphorus removal and also the effect of oxic mixed liquor recycling ratio on nitrate removal has been conducted. In order to observe the nitrate, ammonia and phosphorus removal process efficiency, the experiments were done in a period of three months and in 5 aeration hydraulic residence times, 4, 6, 8, 10 and 12 hours. In these experiments, the returned sludge was 25% and the oxic mixed liquor recycling ratio was 75%. After determining the best hydraulic residence time, experiments continued in 5 different oxic mixed liquor recycling ratios, 75%,150%, 225%, 300% and 375%.
It was concluded that at aeration hydraulic residence time of 8 hours, 96% COD , 95% ammonia and 79% phosphorus (effluent: 9 mg/L COD, 0.87 mg/L ammonia, 2.1 mg/L phosphorus, 18.7 mg/L nitrate) removal were achieved and that was the best HRT. Furthermore, according to the mixed liquor recycling ratio experiments, when the oxic mixed liquor recycling ratio was about 180 - 200%, optimum removing nitrate has been occurred. Although the mixed liquor recycling ratio of 225 - 275% resulted better efficiency for nitrate removal, it is not proposed, because effluent limitations in Iran for the nitrate is up to 10 mg/l which it is resulted in the mixed liquor recycling ratio of 180 -200%, and the other reason is that, with increasing the oxic mixed liquor recycling ratio, energy costs will increase, too.

Results of any dynamic analysis are clearly influenced by the type of the selected acceleration records as the use of inappropriate records can lead to a misunderstanding of the real behavior of structures against earthquakes. For compatibility of accelerograms various criteria including similarity of focal mechanism and magnitude, the same distance from the epicenter, and finally the same soil type of recording stations has been mentioned. Even with respect to these criteria, referencing to databases of earthquakes results in finding several hundreds and sometimes several thousands of apparently suitable accelerograms. Additional measures should be considered to minimize the number of appropriate records. In this paper a three-step screening process is presented during which the number of selected records is quickly reduced from a few thousands to a few number. The finally selected records are the most appropriate for the studied structure regarding the chosen requirements.
In the first stage, called the coarse sieve, ground motion parameters and geological parameters are used to select the records. In the second stage, known as the intermediate sieve, a suit of earthquake records that are more similar in terms of spectral parameters are extracted and in the third and last stage, known as the fine sieve, the final records are selected with studying the spectral shapes of the records. It is shown that the proposed selection method results in a much less scatter in the nonlinear structural responses among the selected earthquakes resulting in an enhanced confidence in the safety of the designed structure.

This work comprises the study of asphalt mixtures produced with cork and rubber granulates as partial aggregate substitutes. Although these alternative materials are considered waste¡ they might contribute to reduce tyre–road interaction noise and therefore¡ to promote pavements’ sustainability. However¡ their incorporation into asphalt mixtures must not compromise their mechanical performance. Thus¡ as a first step to the subject¡ laboratory tests were conducted on two asphalt mixtures containing rubber or cork granulates and their performance was compared to that of a conventional mixture. Promising results were obtained for the alternative mixtures¡ making them ready for testing their acoustic performance.

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.

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.