Search results for: modeling process

Authors: Mehrdad Abkenari, Orod Zarrinkafsh, Mohsen Ramezan Shirazi

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Construction projects initiate in complicated dynamic environments and, due to the close relationships between project parameters and the unknown outer environment, they are faced with several uncertainties and risks. Success in time, cost and quality in large scale construction projects is uncertain in consequence of technological constraints, large number of stakeholders, too much time required, great capital requirements and poor definition of the extent and scope of the project. Projects that are faced with such environments and uncertainties can be well managed through utilization of the concept of risk management in project’s life cycle. Although the concept of risk is dependent on the opinion and idea of management, it suggests the risks of not achieving the project objectives as well. Furthermore, project’s risk analysis discusses the risks of development of inappropriate reactions. Since evaluation and prioritization of construction projects has been a difficult task, the network structure is considered to be an appropriate approach to analyze complex systems; therefore, we have used this structure for analyzing and modeling the issue. On the other hand, we face inadequacy of data in deterministic circumstances, and additionally the expert’s opinions are usually mathematically vague and are introduced in the form of linguistic variables instead of numerical expression. Owing to the fact that fuzzy logic is used for expressing the vagueness and uncertainty, formulation of expert’s opinion in the form of fuzzy numbers can be an appropriate approach. In other words, the evaluation and prioritization of construction projects on the basis of risk factors in real world is a complicated issue with lots of ambiguous qualitative characteristics. In this study, evaluated and prioritization the risk parameters and factors with fuzzy logy method by combination of three method DEMATEL (Decision Making Trial and Evaluation), ANP (Analytic Network Process) and TOPSIS (Technique for Order-Preference by Similarity Ideal Solution) on Construction Management.

Keywords: fuzzy logy, risk, prioritization, assessment

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Authors: Mustapha Kamel Mihoubi, Hocine Dahmani

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The purpose of work is to study the phenomenon of agitation of storm waves at basin caused by different directions of waves relative to the current provision thrown numerical model based on the equation in shallow water using Boussinesq model MIKE 21 BW. According to the diminishing effect of penetration of a wave optimal solution will be available to be reproduced in reduced model. Another alternative arrangement throws will be proposed to reduce the agitation and the effects of the swell reflection caused by the penetration of waves in the harbor.

Keywords: agitation, Boussinesq equations, combination, harbor

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Authors: Mohamed Sadok Bensalem, Soulef Amamria, Khaled Lazzez, Mohamed Ghanmi

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The southern-central Tunisian Atlas presents a typical example of external zone. It occupies a particular position in the North African chains: firstly, it is the eastern limit of atlassicstructures; secondly, it is the edges between the belts structures to the north and the stable Saharan platform in the south. The evolution of deformation studyis based on several methods such as classical or numerical methods. The principals parameters controlling the genesis of folds in the southern central Tunisian Atlas are; the reactivation of pre-existing faults during later compressive phase, the evolution of decollement level, and the relation between thin and thick-skinned. One of the more principal characters of the southern-central Tunisian Atlas is the variation of belts structures directions determined by: NE-SW direction named the attlassic direction in Tunisia, the NW-SE direction carried along the Gafsa fault (the oriental limit of southern atlassic accident), and the E-W direction defined in the southern Tunisian Atlas. This variation of direction is the result of an important variation of deformation during different tectonics phases. A classical modeling of the Jebel ElKebar anticline, based on faults throw of the pre-existing faults and its reactivation during compressive phases, shows the importance of extensional deformation, particular during Aptian-Albian period, comparing with that of later compression (Alpine phases). A numerical modeling, based on the software Rampe E.M. 1.5.0, applied on the anticline of Jebel Orbata confirms the interpretation of “fault related fold” with decollement level within the Triassic successions. The other important parameter of evolution of deformation is the vertical migration of decollement level; indeed, more than the decollement level is in the recent series, most that the deformation is accentuated. The evolution of deformation is marked the development of duplex structure in Jebel AtTaghli (eastern limit of Jebel Orbata). Consequently, the evolution of deformation is proportional to the depth of the decollement level, the most important deformation is in the higher successions; thus is associated to the thin-skinned deformation; the decollement level permit the passive transfer of deformation in the cover.

Keywords: evolution of deformation, pre-existing faults, decollement level, thin-skinned

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Authors: Jihene Jebeniani

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We proposed an approach combining both the techniques of experimental economy and the flexibility of discrete choice models in order to test the loss aversion. Our main objective was to test the loss aversion of the Cumulative Prospect Theory (CPT). We developed an experimental laboratory in the context of the financial investments that aimed to analyze the attitude towards the risk of the investors. The study uses the lotteries and is basing on econometric modeling. The estimated model was the ordered probit.

Keywords: risk aversion, behavioral finance, experimental economic, lotteries, cumulative prospect theory

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Authors: Mahalakshmi Vivekanandan S.

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As per the recent changes happening in the global policies, climate-related changes and the impact it causes across every sector are viewed as green swan events – in essence, climate-related changes can often happen and lead to risk and a lot of uncertainty, but needs to be mitigated instead of considering them as black swan events. This brings about a question on how this risk can be computed so that the financial institutions can plan to mitigate it. Climate-related changes impact all risk types – credit risk, market risk, operational risk, liquidity risk, reputational risk and other risk types. And the models required to compute this has to consider the different industrial needs of the counterparty, as well as the factors that are contributing to this – be it in the form of different risk drivers, or the different transmission channels or the different approaches and the granular form of data availability. This brings out the suggestion that the climate-related changes, though it affects Pillar I risks, will be a Pillar II risk. This has to be modeled specifically based on the financial institution’s actual exposure to different industries instead of generalizing the risk charge. And this will have to be considered as the additional capital to be met by the financial institution in addition to their Pillar I risks, as well as the existing Pillar II risks. In this paper, the author presents a risk assessment framework to model and assess climate change risks - for both credit and market risks. This framework helps in assessing the different scenarios and how the different transition risks affect the risk associated with the different parties. This research paper delves into the topic of the increase in the concentration of greenhouse gases that in turn cause global warming. It then considers the various scenarios of having the different risk drivers impacting the Credit and market risk of an institution by understanding the transmission channels and also considering the transition risk. The paper then focuses on the industry that’s fast seeing a disruption: the automobile industry. The paper uses the framework to show how the climate changes and the change to the relevant policies have impacted the entire financial institution. Appropriate statistical models for forecasting, anomaly detection and scenario modeling are built to demonstrate how the framework can be used by the relevant agencies to understand their financial risks. The paper also focuses on the climate risk calculation for the Pillar II Capital calculations and how it will make sense for the bank to maintain this in addition to their regular Pillar I and Pillar II capital.

Keywords: capital calculation, climate risk, credit risk, pillar ii risk, scenario modeling

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Authors: Huda Al Shuaily, Karen Renaud

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Databases comprise the foundation of most software systems. System developers inevitably write code to query these databases. The de facto language for querying is SQL and this, consequently, is the default language taught by higher education institutions. There is evidence that learners find it hard to master SQL, harder than mastering other programming languages such as Java. Educators do not agree about explanations for this seeming anomaly. Further investigation may well reveal the reasons. In this paper, we report on our investigations into how novices learn SQL, the actual problems they experience when writing SQL, as well as the differences between expert and novice SQL query writers. We conclude by presenting a model of SQL learning that should inform the instructional material design process better to support the SQL learning process.

Keywords: pattern, SQL, learning, model

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Authors: Dunwen Zuo, Yongfang Deng, Bo Song

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An attempt is made here to measure the forces of three directions, under conditions of different feed speeds, different tilt angles of tool and without or with the pin on the tool, by using octagonal ring dynamometer in the AA2024 aluminum FSJ (Friction Stir Joining) process, and investigate how four main factors influence forces in the FSJ process. It is found that, high feed speed lead to small feed force and small lateral force, but high feed speed leads to large feed force in the stable joining stage of process. As the rotational speed increasing, the time of axial force drop from the maximum to the minimum required increased in the push-up process. In the stable joining stage, the rotational speed has little effect on the feed force; large rotational speed leads to small lateral force and axial force. The maximum axial force increases as the tilt angle of tool increases at the downward movement stage. At the moment of start feeding, as tilt angle of tool increases, the amplitudes of the axial force increasing become large. In the stable joining stage, with the increase of tilt angle of tool, the axial force is increased, the lateral force is decreased, and the feed force almost unchanged. The tool with pin will decrease axial force in the downward movement stage. The feed force and lateral force will increase, but the axial force will reduced in the stable joining stage by using the tool with pin compare to by using the tool without pin.

Keywords: FSJ, force factor, AA2024 aluminum, friction stir joining

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Authors: Thien Bach Nguyen, Nhu-Van Nguyen, Phi-Minh Nguyen, Minh Hien Dao

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The external store safe separation evaluation process implementing CFD and MIL-HDBK-1763 is proposed to support the evaluation and compliance of the external store safe separation with the extensive using CFD and the criteria from MIL-HDBK-1763. The criteria of safe separation are researched and investigated for the various standards and handbooks such as MIL-HDBK-1763, MIL-HDBK-244A, AGARD-AG-202 and AGARD-AG-300 to acquire the appropriate and tailored values and limits for the typical applications of external carriages and aircraft fighters. The CFD and 6DOF simulations are extensively used in ANSYS 2023 R1 Software for verification and validation of moving unstructured meshes and solvers by calibrating the position, aerodynamic forces and moments of the existing air-to-ground missile models. The verified CFD and 6DoF simulation separation process is applied and implemented for the investigation of the typical munition separation phenomena and compliance with the tailored requirements of MIL-HDBK-1763. The prediction of munition trajectory parameters under aircraft aerodynamics interference and specified rack unit consideration after munition separation is provided and complied with the tailored requirements to support the safe separation evaluation of improved and newly external store munition before the flight test performed. The proposed process demonstrates the effectiveness and reliability in providing the understanding of the complicated store separation and the reduction of flight test sorties during the improved and new munition development projects by extensively using the CFD and tailoring the existing standards.

Keywords: external store separation, MIL-HDBK-1763, CFD, moving meshes, flight test data, munition.

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Authors: R. Berrached, H. Ait Mahamed, A. Iddou

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Water pollution is nowadays a serious problem, due to the increasing scarcity of water and thus to the impact induced by such pollution on the human health. Various techniques are made use of to deal with water pollution. Among the most used ones, some can be enumerated: the bacterian bed, the activated sludge, lagoons as biological processes and coagulation-flocculation as a physic-chemical process. These processes are very expensive and a decreasing in efficiency treatment with the increase of the initial pollutants concentration. This is the reason why research has been reoriented towards the use of adsorption process as an alternative solution instead of the other traditional processes. In our study, we have tempted to explore the characteristics of hydroxides of Al and Fe to purify contaminated water by two industrial dyes SBL blue and SRL-150 orange. Results have shown the efficiency of the two materials on the blue SBL dye.

Keywords: metallic hydroxydes, dyes, purification, adsorption

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Authors: Gabriel Quintero

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This paper presents the result of the implementation of a series of algorithms intended to be used for representing in most of the 3D geographic software, even Google Earth, the subsurface formations properties combining 2D charts or 3D plots over a 3D background, allowing everyone to use them, no matter the economic size of the company for which they work. Besides the existence of complex and expensive specialized software for modeling subsurface formations based on the same information provided to this one, the use of this open source development shows a higher and easier usability and good results, limiting the rendered properties and polygons to a basic set of charts and tubes.

Keywords: chart, earth, formations, subsurface, visualization

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Authors: Senthil Kumar Anantharaman

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Providing telecommunications based network services in developing countries like India which has a population of 1.5 billion people, so that these services reach every individual, is one of the greatest challenges the country has been facing in its journey towards economic growth and development. With growing number of telecommunications service providers in the country, a constant challenge that has been faced by these providers is in providing not only quality but also delightful customer experience while simultaneously generating enhanced revenues and profits. Thus, the role played by process improvement methodologies like Six Sigma cannot be undermined and specifically in telecom service provider based operations, it has provided substantial benefits. Therefore, it advantages are quite comparable to its applications and advantages in other sectors like manufacturing, financial services, information technology-based services and Healthcare services. One of the key reasons that this methodology has been able to reap great benefits in telecommunications sector is that this methodology has been combined with many of its competing process improvement techniques like Theory of Constraints, Lean and Kaizen to give the maximum benefit to the service providers thereby creating a winning combination of organized process improvement methods for operational excellence thereby leading to business excellence. This paper discusses about some of the key projects and areas in the end to end ‘Quote to Cash’ process at big three Indian telecommunication companies that have been highly assisted by applying Six Sigma along with other process improvement techniques. While the telecommunication companies which we have considered, is primarily in India and run by both private operators and government based setups, the methodology can be applied equally well in any other part of developing countries around the world having similar context. This study also compares the enhanced revenues that can arise out of appropriate opportunities in emerging market scenarios, that Six Sigma as a philosophy and methodology can provide if applied with vigour and robustness. Finally, the paper also comes out with a winning framework in combining Six Sigma methodology with Kaizen, Lean and Theory of Constraints that will enhance both the top-line as well as the bottom-line while providing the customers a delightful experience.

Keywords: emerging markets, lean, process improvement, six sigma, telecommunications, theory of constraints

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Authors: Gezahegn Gizaw

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The FDRE Tourism Training Institute organizes forums for debates, best practices exchange and focus group discussions to forge a sustainable and growing tourism sector while minimizing negative impacts on the environment, communities, and cultures. This study aimed at applying empirical research method to identify and quantify relative importance of success factors and individual engagement indicators that were identified in these forums. Response to the 12-question survey was collected from a total of 437 respondents in academic training institutes (212), business executive and employee (204) and non-academic government offices (21). Overall, capacity building was perceived as the most important driver of success for stakeholder engagement. Business executive and employee category rated capacity building as the most important driver of success (53%), followed by decision-making process (27%) and community participation (20%). Among educators and students, both capacity building and decision-making process were perceived as the most important factors (40% of respondents), whereas community participation was perceived as the most important success factor only by 20% of respondents. Individual engagement score in capacity building, decision-making process and community participation showed highest variability by educational level of participants (variance of 3.4% - 5.2%, p<0.001). Individual engagement score in capacity building was highly correlated to perceived benefit of training on improved efficiency, job security, higher customer satisfaction and self-esteem. On the other hand, individual engagement score in decision making process was highly correlated to its perceived benefit on lowering business costs, improving ability to meet the needs of a target market, job security, self-esteem and more teamwork. The study provides a set of recommendations that help educators, business executives and policy makers to maximize the individual and synergetic effect of training, decision making process on sustainability and growth of the tourism sector in Ethiopia.

Keywords: engagement score, driver of success, capacity building, tourism

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Authors: Emmanuel Billy

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This work is in the CABRISS project (H2020 projects) which aims at developing innovative cost-effective methods for the extraction of materials from the different sources of PV waste: Si based panels, thin film panels or Si water diluted slurries. Aluminum, silicon, indium, and silver will especially be extracted from these wastes in order to constitute materials feedstock which can be used later in a closed-loop process. The extraction of metals from silicon solar cells is often an energy-intensive process. It requires either smelting or leaching at elevated temperature, or the use of large quantities of strong acids or bases that require energy to produce. The energy input equates to a significant cost and an associated CO2 footprint, both of which it would be desirable to reduce. Thus there is a need to develop more energy-efficient and environmentally-compatible processes. Thus, ‘ionometallurgy’ could offer a new set of environmentally-benign process for metallurgy. This work demonstrates that ionic liquids provide one such method since they can be used to dissolve and recover silver. The overall process associates leaching, recovery and the possibility to re-use the solution in closed-loop process. This study aims to evaluate and compare different ionic liquids to leach and recover silver. An electrochemical analysis is first implemented to define the best system for the Ag dissolution. Effects of temperature, concentration and oxidizing agent are evaluated by this approach. Further, a comparative study between conventional approach (nitric acid, thiourea) and the ionic liquids (Cu and Al) focused on the leaching efficiency is conducted. A specific attention has been paid to the selection of the Ionic Liquids. Electrolytes composed of chelating anions are used to facilitate the lixiviation (Cl, Br, I,), avoid problems dealing with solubility issues of metallic species and of classical additional ligands. This approach reduces the cost of the process and facilitates the re-use of the leaching medium. To define the most suitable ionic liquids, electrochemical experiments have been carried out to evaluate the oxidation potential of silver include in the crystalline solar cells. Then, chemical dissolution of metals for crystalline solar cells have been performed for the most promising ionic liquids. After the chemical dissolution, electrodeposition has been performed to recover silver under a metallic form.

Keywords: electrodeposition, ionometallurgy, leaching, recycling, silver

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Authors: N. Naz, A. D. Domenico, M. N. Huda

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Soft Robotics is a rapidly growing multidisciplinary field where robots are fabricated using highly deformable materials motivated by bioinspired designs. The high dexterity and adaptability to the external environments during contact make soft robots ideal for applications such as gripping delicate objects, locomotion, and biomedical devices. The actuation system of soft robots mainly includes fluidic, tendon-driven, and smart material actuation. Among them, Soft Pneumatic Actuator, also known as SPA, remains the most popular choice due to its flexibility, safety, easy implementation, and cost-effectiveness. However, at present, most of the fabrication of SPA is still based on traditional molding and casting techniques where the mold is 3d printed into which silicone rubber is cast and consolidated. This conventional method is time-consuming and involves intensive manual labour with the limitation of repeatability and accuracy in design. Recent advancements in direct 3d printing of different soft materials can significantly reduce the repetitive manual task with an ability to fabricate complex geometries and multicomponent designs in a single manufacturing step. The aim of this research work is to design and analyse the Soft Pneumatic Actuator (SPA) utilizing both conventional casting and modern direct 3d printing technologies. The mold of the SPA for traditional casting is 3d printed using fused deposition modeling (FDM) with the polylactic acid (PLA) thermoplastic wire. Hyperelastic soft materials such as Ecoflex-0030/0050 are cast into the mold and consolidated using a lab oven. The bending behaviour is observed experimentally with different pressures of air compressor to ensure uniform bending without any failure. For direct 3D-printing of SPA fused deposition modeling (FDM) with thermoplastic polyurethane (TPU) and stereolithography (SLA) with an elastic resin are used. The actuator is modeled using the finite element method (FEM) to analyse the nonlinear bending behaviour, stress concentration and strain distribution of different hyperelastic materials after pressurization. FEM analysis is carried out using Ansys Workbench software with a Yeon-2nd order hyperelastic material model. FEM includes long-shape deformation, contact between surfaces, and gravity influences. For mesh generation, quadratic tetrahedron, hybrid, and constant pressure mesh are used. SPA is connected to a baseplate that is in connection with the air compressor. A fixed boundary is applied on the baseplate, and static pressure is applied orthogonally to all surfaces of the internal chambers and channels with a closed continuum model. The simulated results from FEM are compared with the experimental results. The experiments are performed in a laboratory set-up where the developed SPA is connected to a compressed air source with a pressure gauge. A comparison study based on performance analysis is done between FDM and SLA printed SPA with the molded counterparts. Furthermore, the molded and 3d printed SPA has been used to develop a three-finger soft pneumatic gripper and has been tested for handling delicate objects.

Keywords: finite element method, fused deposition modeling, hyperelastic, soft pneumatic actuator

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Authors: M. Dakshayini, P. Jayarekha

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In traditional output-based education system, class room lecture and laboratory are the traditional delivery methods used during the course. Written examination and lab examination have been used as a conventional tool for evaluating student’s performance. Hence, there are certain apprehensions that the traditional education system may not efficiently prepare the students for competent professional life. This has led for the change from Traditional output-based education to Outcome-Based Education (OBE). OBE first sets the ideal programme learning outcome consecutively on increasing degree of complexity that students are expected to master. The core curriculum, teaching methodologies and assessment tools are then designed to achieve the proposed outcomes mainly focusing on what students can actually attain after they are taught. In this paper, we discuss a promising applications based learning and evaluation component involving industry collaboration to improve the quality of teaching and student learning process. Incorporation of this component definitely improves the quality of student learning in engineering education and helps the student to attain the competency as per the graduate attributes. This may also reduce the Industry-academia gap.

Keywords: outcome-based education, programme learning outcome, teaching-learning process, evaluation, industry collaboration

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Authors: H. Hammoudi, S. Bendenia, I. Batonneau-Gener, A. Khelifa

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Applying growing zeolites is due to their intrinsic physicochemical properties: a porous structure, regular, generating a large free volume, a high specific surface area, acidic properties of interest to the origin of their activity, selectivity energy and dimensional, leading to a screening phenomenon, hence the name of molecular sieves is generally attributed to them. Most of the special properties of zeolites have been valued as direct applications such as ion exchange, adsorption, separation and catalysis. Due to their crystalline structure stable, their large pore volume and their high content of cation X zeolites are widely used in the process of adsorption and separation. The acidic properties of zeolites X and interesting selectivity conferred on them their porous structure is also have potential catalysts. The study presented in this manuscript is devoted to the chemical modification of an X zeolite by cation exchange. Ion exchange of zeolite NaX by Zn 2 + cations and / or Cu 2 + is gradually conducted by following the evolution of some of its characteristics: crystallinity by XRD, micropore volume by nitrogen adsorption. Once characterized, the different samples will be used for the adsorption of propane and propylene. Particular attention is paid thereafter, on the modeling of adsorption isotherms. In this vein, various equations of adsorption isotherms and localized mobile, some taking into account the adsorbate-adsorbate interactions, are used to describe the experimental isotherms. We also used the Toth equation, a mathematical model with three parameters whose adjustment requires nonlinear regression. The last part is dedicated to the study of acid properties of Cu (x) X, Zn (x) X and CuZn (x) X, with the adsorption-desorption of pyridine followed by IR. The effect of substitution at different rates of Na + by Cu2 + cations and / or Zn 2 +, on the crystallinity and on the textural properties was treated. Some results on the morphology of the crystallites and the thermal effects during a temperature rise, obtained by scanning electron microscopy and DTA-TGA thermal analyzer, respectively, are also reported. The acidity of our different samples was also studied. Thus, the nature and strength of each type of acidity are estimated. The evaluation of these various features will provide a comparison between Cu (x) X, Zn (x) X and CuZn (x) X. One study on adsorption of C3H8 and C3H6 in NaX, Cu (x) X , Zn (x) x and CuZn (x) x has been undertaken.

Keywords: adsorption, acidity, ion exchange, zeolite

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Authors: Mohammad H. Yarmohammadian, Masoud Ferdosi, Abbas Haghshenas, Fatemeh Rezaei

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Surgical procedures aim at preserving human life and improving quality of their life. However, there are many potential risk sources that can cause serious harm to patients. For centuries, managers believed that technical competence of a surgeon is the only key to a successful surgery. But over the past decade, risks are considered in terms of process-based safety procedures, teamwork and inter departmental communication. Aims: This study aims to determine how the process- biased surgical risk management should be done in terms of project management tool named ABS (Activity Breakdown Structure). Settings and Design: This study was conducted in two stages. First, literature review and meeting with professors was done to determine principles and framework of surgical risk management. Next, responsible teams for surgical patient journey were involved in following meeting to develop the process- biased surgical risk management. Methods and Material: This study is a qualitative research in which focus groups with the inductive approach is used. Sampling was performed to achieve representativeness through intensity sampling biased on experience and seniority. Analysis Method used: context analysis of interviews and consensus themes extracted from FDG meetings discussion was the analysis tool. Results: we developed the patient journey process in 5 main phases, 24 activities and 108 tasks. Then, responsible teams, transposition and allocated places for performing determined. Some activities and tasks themes were repeated in each phases like patient identification and records review because of their importance. Conclusions: Risk management of surgical departments is significant as this facility is the hospital’s largest cost and revenue center. Good communication between surgical team and other clinical teams outside surgery department through process- biased perspective could improve safety of patient under this procedure.

Keywords: risk management, activity breakdown structure (ABS), surgical department, medical sciences

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Authors: Cigdem Safak Saglam

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Most thermal power plants use steam as working fluid in their power cycle. Therefore, in addition to fuel, water is the other main input for thermal plants. Water and steam must be highly pure in order to protect the systems from corrosion, scaling and biofouling. Pure process water is produced in water treatment plants having many several treatment methods. Treatment plant design is selected depending on raw water source and required water quality. Although working principle of fossil-fuel fired thermal power plants are same, there is no standard design and equipment arrangement valid for all thermal power plant utility systems. Besides that, there are many other technology evaluation and selection criteria for designing the most optimal water systems meeting the requirements such as local conditions, environmental restrictions, electricity and other consumables availability and transport, process water sources and scarcity, land use constraints etc. Aim of this study is explaining the adopted methodology for technology selection for process water preparation and industrial waste water treatment plant in a thermal power plant project located in Tufanbeyli, Adana Province in Turkey. Thermal power plant is fired with indigenous lignite coal extracted from adjacent lignite reserves. This paper addresses all above-mentioned factors affecting the thermal power plant water treatment facilities (demineralization + waste water treatment) design and describes the ultimate design of Tufanbeyli Thermal Power Plant Water Treatment Plant.

Keywords: thermal power plant, lignite coal, pretreatment, demineralization, electrodialysis, recycling, ash dampening

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Authors: M. Cortés, E. Vera, M. Avella

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Corrosion is an imminent process in nature, which affects all types of materials. In sewerage systems, the corrosion process caused by microorganisms, also known as biogenic sulfuric acid attack, has been studied. This affects the structural integrity of the concrete drainage pipes and the sewage treatment plants. This article is a review of research which focuses on the study of how to reduce the production of hydrogen sulfide, how to improve the resistance of concrete through the use of additives and the implementation of antimicrobial techniques to reduce bacterial growth.

Keywords: bactericides, biogenic sulfuric acid, corrosion, concrete, hydrogen sulphide, nano materials, zeolites

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Authors: Leila Mohammadi

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This paper presents the impact of persuasive communication implemented by fertility clinics websites, and how this information influences women at their decision-making for undertaking this procedure. The influential factors for women decisions to do social egg freezing (SEF) are analyzed from a framing theory perspective, with a specific focus on the impact of persuasive information on women’s decision making. This study follows a quantitative approach. A two-phase survey has been conducted to examine the interest rate to undertake SEF. In the first phase, a questionnaire was available during a month (May 2015) to women to answer whether or not they knew enough information of this process, with a total of 230 answers. The second phase took place in the two last weeks of July 2015. All the respondents were invited to a seminars called ‘All about egg freezing’ and afretwards they were requested to answer the second questionnaire. After the seminar, in which they were given an extensive amount of information about egg freezing, a total of 115 women replied the questionnaire. The collected data during this process were analyzed using descriptive statistics. Most of the respondents changed their opinion in the second questionaire which was after receiving information. Although in the first questionnaire their self-evaluation of having knowledge about this process and the implemented technologies was very high, they realized that they still need to access more information from different sources in order to be able to make a decision. The study reached the conclusion that persuasive and framed information by clinics would affect the decisions of these women. Despite the reasons women have to do egg freezing and their motivations behind it, providing people necessary information and unprejudiced data about this process (such as its positive and negative aspects, requirements, suppositions, possibilities and consequences) would help them to make a more precise and reasonable decision about what they are buying.

Keywords: decision making, fertility clinics, framing theory, persuasive information, social egg freezing

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Authors: Alexandra-Veronica Luca, Letitia Petrescu

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Steel production is a major contributor to global warming potential. An average value of 1.83 tons of CO₂ is emitted for every ton of steel produced, resulting in over 3.3 Mt of CO₂ emissions each year. The present paper is focused on the investigation and comparison of two O₂ separation methods and two CO₂ capture technologies applicable to iron and steel industry. The O₂ used in steel production comes from an Air Separation Unit (ASU) using distillation or from air separation using membranes. The CO₂ capture technologies are represented by a two-stage membrane separation process and the gas-liquid absorption using methyl di-ethanol amine (MDEA). Process modelling and simulation tools, as well as environmental tools, are used in the present study. The production capacity of the steel mill is 4,000,000 tones/year. In order to compare the two CO₂ capture technologies in terms of efficiency, performance, and sustainability, the following cases have been investigated: Case 1: steel production using O₂ from ASU and no CO₂ capture; Case 2: steel production using O₂ from ASU and gas-liquid absorption for CO₂ capture; Case 3: steel production using O₂ from ASU and membranes for CO₂ capture; Case 4: steel production using O₂ from membrane separation method and gas-liquid absorption for CO₂ capture and Case-5: steel production using membranes for air separation and CO₂ capture. The O₂ separation rate obtained in the distillation technology was about 96%, and about 33% in the membrane technology. Similarly, the O₂ purity resulting in the conventional process (i.e. distillation) is higher compared to the O₂ purity obtained in the membrane unit (e.g., 99.50% vs. 73.66%). The air flow-rate required for membrane separation is about three times higher compared to the air flow-rate for cryogenic distillation (e.g., 549,096.93 kg/h vs. 189,743.82 kg/h). A CO₂ capture rate of 93.97% was obtained in the membrane case, while the CO₂ capture rate for the gas-liquid absorption was 89.97%. A quantity of 6,626.49 kg/h CO₂ with a purity of 95.45% is separated from the total 23,352.83 kg/h flue-gas in the membrane process, while with absorption of 6,173.94 kg/h CO₂ with a purity of 98.79% is obtained from 21,902.04 kg/h flue-gas and 156,041.80 kg/h MDEA is recycled. The simulation results, performed using ChemCAD process simulator software, lead to the conclusion that membrane-based technology can be a suitable alternative for CO₂ removal for steel production. An environmental evaluation using Life Cycle Assessment (LCA) methodology was also performed. Considering the electricity consumption, the performance, and environmental indicators, Case 3 can be considered the most effective. The environmental evaluation, performed using GaBi software, shows that membrane technology can lead to lower environmental emissions if membrane production is based on benzene derived from toluene hydrodealkilation and chlorine and sodium hydroxide are produced using mixed technologies.

Keywords: CO₂ capture, gas-liquid absorption, Life Cycle Assessment, membrane separation, steel production

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Authors: A. Anbu Raj, V. Mugendiren

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Sheet metal forming is a vital manufacturing process used in automobile, aerospace, agricultural industries, etc. Incremental forming is a promising process providing a short and inexpensive way of forming complex three-dimensional parts without using die. The aim of this research is to study the forming behaviour of AA 5052, Aluminium Alloy, using incremental forming and also to study the FLD of cone shape AA 5052 Aluminium Alloy at room temperature and various annealing temperature. Initially the surface roughness and wall thickness through incremental forming on AA 5052 Aluminium Alloy sheet at room temperature is optimized by controlling the effects of forming parameters. The central composite design (CCD) was utilized to plan the experiment. The step depth, feed rate, and spindle speed were considered as input parameters in this study. The surface roughness and wall thickness were used as output response. The process performances such as average thickness and surface roughness were evaluated. The optimized results are taken for minimum surface roughness and maximum wall thickness. The optimal results are determined based on response surface methodology and the analysis of variance. Formability Limit Diagram is constructed on AA 5052 Aluminium Alloy at room temperature and various annealing temperature by using optimized process parameters from the response surface methodology. The cone has higher formability than the square pyramid and higher wall thickness distribution. Finally the FLD on cone shape and square pyramid shape at room temperature and the various annealing temperature is compared experimentally and simulated with Abaqus software.

Keywords: incremental forming, response surface methodology, optimization, wall thickness, surface roughness

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Authors: Hwang Ho Kim, Do Gyun Kim, Jin Young Choi, Sang Chul Park

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Since tire production process is very complicated, company-wide management of it is very difficult, necessitating considerable amounts of capital and labors. Thus, productivity should be enhanced and maintained competitive by developing and applying effective production plans. Among major processes for tire manufacturing, consisting of mixing component preparation, building and curing, the mixing process is an essential and important step because the main component of tire, called compound, is formed at this step. Compound as a rubber synthesis with various characteristics plays its own role required for a tire as a finished product. Meanwhile, scheduling tire mixing process is similar to flexible job shop scheduling problem (FJSSP) because various kinds of compounds have their unique orders of operations, and a set of alternative machines can be used to process each operation. In addition, setup time required for different operations may differ due to alteration of additives. In other words, each operation of mixing processes requires different setup time depending on the previous one, and this kind of feature, called sequence dependent setup time (SDST), is a very important issue in traditional scheduling problems such as flexible job shop scheduling problems. However, despite of its importance, there exist few research works dealing with the tire mixing process. Thus, in this paper, we consider the scheduling problem for tire mixing process and suggest an efficient particle swarm optimization (PSO) algorithm to minimize the makespan for completing all the required jobs belonging to the process. Specifically, we design a particle encoding scheme for the considered scheduling problem, including a processing sequence for compounds and machine allocation information for each job operation, and a method for generating a tire mixing schedule from a given particle. At each iteration, the coordination and velocity of particles are updated, and the current solution is compared with new solution. This procedure is repeated until a stopping condition is satisfied. The performance of the proposed algorithm is validated through a numerical experiment by using some small-sized problem instances expressing the tire mixing process. Furthermore, we compare the solution of the proposed algorithm with it obtained by solving a mixed integer linear programming (MILP) model developed in previous research work. As for performance measure, we define an error rate which can evaluate the difference between two solutions. As a result, we show that PSO algorithm proposed in this paper outperforms MILP model with respect to the effectiveness and efficiency. As the direction for future work, we plan to consider scheduling problems in other processes such as building, curing. We can also extend our current work by considering other performance measures such as weighted makespan or processing times affected by aging or learning effects.

Keywords: compound, error rate, flexible job shop scheduling problem, makespan, particle encoding scheme, particle swarm optimization, sequence dependent setup time, tire mixing process

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Authors: Sandip Sharma, Jayesh Ruparelia

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The present work focuses on the comparative study of ozone based advanced oxidation processes (AOPs): O3, O3/UV and O3/UV/Persulfate for mineralization of synthetic wastewater containing Reactive Black5 (RB5) dye. The effect of various parameters: pH, ozone flow rate, initial concentration of dye and intensity of UV light was analyzed to access performance efficiency of AOPs. The performance of all the three AOPs was evaluated on the basis of decolorization, % TOC removal and ozone consumption. The highest mineralization rate of 86.83% was achieved for O3/UV/Persulfate followed by 71.53% and 66.82 % for O3/UV and O3 respectively. This is attributed to the fact that Persulfate ions (S2O82-) upon activation produce sulfate radical (SO4-●) which is very strong oxidant capable of degrading a wide variety of recalcitrant organic compounds, moreover to enhance the performance of Persulfate it is activated using UV irradiation. On increasing the intensity of UV irradiation from 11W to 66W, TOC removal efficiency is increased by 59.04%. Ozone based AOPs gives better mineralization on basic conditions, at pH 12 it gives 68.81%, 60.01% and 40.32% TOC removal for O3/UV/Persulfate, O3/UV and O3 process respectively. The result also reveals that decolorization of 98.95%, 95.17% and 94.71% was achieved by O3/UV/Persulfate, O3/UV and O3 process respectively. In addition to above, ozone consumption was also considerably decreased by 17% in case of O3/UV/Persulfate, as efficiency of process is enhanced by means of activation of persulfate through UV irradiation. Thus study reveals that mineralization follows: O3/UV/Persulfate> O3/UV> O3.

Keywords: AOP, mineralization, TOC, recalcitrant organic compounds

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Authors: Awadh O. Al-Anazi

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As part of the organizational needs toward successful maintaining activities, a proper management system need to be put in place, ensuring the effectiveness of maintenance activities. The management system shall clearly describes the process of identifying, prioritizing, planning, scheduling, execution, and providing valuable feedback for all maintenance activities. Completion and accuracy of the system with proper implementation shall provide the organization with a strong platform for effective maintenance activities that are resulted in efficient outcomes toward business success. The purpose of this research was to introduce a practical tool for measuring the maintenance efficiency level within Saudi organizations. A comprehensive study was launched across many maintenance professionals throughout Saudi leading organizations. The study covered five main categories: work process, identification, planning and scheduling, execution, and performance monitoring. Each category was evaluated across many dimensions to determine its current effectiveness through a five-level scale from 'process is not there' to 'mature implementation'. Wide participation was received, responses were analyzed, and the study was concluded by highlighting major gaps and improvement opportunities within Saudi organizations. One effective implementation of the efficiency enhancement efforts was deployed in Saudi Kayan (one of Sabic affiliates). Below details describes the project outcomes: SK overall maintenance wrench time was measured at 20% (on average) from the total daily working time. The assessment indicates the appearance of several organizational gaps, such as a high amount of reactive work, poor coordination and teamwork, Unclear roles and responsibilities, as well as underutilization of resources. Multidiscipline team was assigned to design and implement an appropriate work process that is capable to govern the execution process, improve the maintenance workforce efficiency, and maximize wrench time (targeting > 50%). The enhanced work process was introduced through brainstorming and wide benchmarking, incorporated with a proper change management plan and leadership sponsorship. The project was completed in 2018. Achieved Results: SK WT was improved to 50%, which resulted in 1) reducing the Average Notification completion time. 2) reducing maintenance expenses on OT and manpower support (3.6 MSAR Actual Saving from Budget within 6 months).

Keywords: efficiency, enhancement, maintenance, work force, wrench time

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Authors: Mustafa Dogru, Ruveyda Komurlu

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Companies and professionals in the construction sector face various risks in every project depending on the characteristics, size, complexity, the location of the projects and the techniques used. Some risks’ effects may increase as the project progresses whereas new risks may emerge. Because of the ever-changing nature of the risks, risk management is a cyclical process that needs to be repeated throughout the project. Since the risks threaten the success of the project, risk management is an important part of the entire project management process. The aims of this study are to emphasize the importance of risk management in construction projects, summarize the risk identification process, and introduce a number of methods for preventing risks such as alternative design, checklists, prototyping and test-analysis-correction technique etc. Following the literature review conducted to list the techniques for preventing risks, case studies has been performed to compare and evaluate the success of the techniques in a number of completed projects with the same typology, performed domestic and international. Findings of the study suggest that controlling and minimizing the level of the risks in construction projects, taking optimal precautions for different risks, and mitigating or eliminating the effects of risks are important in order to prevent additional costs for the project. Additionally, focusing on the risks that have highest impact is the most rational way to minimize the effects of the risks on projects.

Keywords: construction projects, construction management, project management, risk management

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Authors: Mohsen Goodarzi, George Berghorn

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Despite the rapid growth in the number of green building and community development projects, the long-term performance of these projects has not yet been sufficiently evaluated from the users’ points of view. This is partially due to the lack of post-occupancy evaluation tools available for this type of project. In this study, a post-construction evaluation model is developed to evaluate the relationship between the perceived performance and satisfaction of residents in LEED-certified residential buildings and communities. To develop this evaluation model, a primary five-factor model was developed based on the existing models and residential satisfaction theories. Each factor of the model included several measures that were adopted from LEED certification systems such as LEED-BD+C New Construction, LEED-BD+C Multifamily Midrise, LEED-ND, as well as the UC Berkeley’s Center for the Built Environment survey tool. The model included four predictor variables (factors), including perceived building performance (8 measures), perceived infrastructure performance (9 measures), perceived neighborhood design (6 measures), and perceived economic performance (4 measures), and one dependent variable (factor), which was residential satisfaction (6 measures). An online survey was then conducted to collect the data from the residents of LEED-certified residential communities (n=192) and the validity of the model was tested through Confirmatory Factor Analysis (CFA). After modifying the CFA model, 26 measures, out of the initial 33 measures, were retained to enter into a Structural Equation Model (SEM) and to find the relationships between the perceived buildings performance, infrastructure performance, neighborhood design, economic performance and residential Satisfaction. The results of the SEM showed that the perceived building performance was the most influential factor in determining residential satisfaction in LEED-certified communities, followed by the perceived neighborhood design. On the other hand, perceived infrastructure performance and perceived economic performance did not show any significant relationship with residential satisfaction in these communities. This study can benefit green building researchers by providing a model for the evaluation of the long-term performance of these projects. It can also provide opportunities for green building practitioners to determine priorities for future residential development projects.

Keywords: green building, residential satisfaction, perceived performance, confirmatory factor analysis, structural equation modeling

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Authors: Dino Carpentras, Alejandro Dinkelberg, Michael Quayle

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Opinion dynamics models use an agent-based modeling approach to model people’s opinions. Model's properties are usually explored by testing the two 'degrees of freedom': the interaction rule and the network topology. The latter defines the connection, and thus the possible interaction, among agents. The interaction rule, instead, determines how agents select each other and update their own opinion. Here we show the existence of the third degree of freedom. This can be used for turning one model into each other or to change the model’s output up to 100% of its initial value. Opinion dynamics models represent the evolution of real-world opinions parsimoniously. Thus, it is fundamental to know how real-world opinion (e.g., supporting a candidate) could be turned into a number. Specifically, we want to know if, by choosing a different opinion-to-number transformation, the model’s dynamics would be preserved. This transformation is typically not addressed in opinion dynamics literature. However, it has already been studied in psychometrics, a branch of psychology. In this field, real-world opinions are converted into numbers using abstract objects called 'scales.' These scales can be converted one into the other, in the same way as we convert meters to feet. Thus, in our work, we analyze how this scale transformation may affect opinion dynamics models. We perform our analysis both using mathematical modeling and validating it via agent-based simulations. To distinguish between scale transformation and measurement error, we first analyze the case of perfect scales (i.e., no error or noise). Here we show that a scale transformation may change the model’s dynamics up to a qualitative level. Meaning that a researcher may reach a totally different conclusion, even using the same dataset just by slightly changing the way data are pre-processed. Indeed, we quantify that this effect may alter the model’s output by 100%. By using two models from the standard literature, we show that a scale transformation can transform one model into the other. This transformation is exact, and it holds for every result. Lastly, we also test the case of using real-world data (i.e., finite precision). We perform this test using a 7-points Likert scale, showing how even a small scale change may result in different predictions or a number of opinion clusters. Because of this, we think that scale transformation should be considered as a third-degree of freedom for opinion dynamics. Indeed, its properties have a strong impact both on theoretical models and for their application to real-world data.

Keywords: degrees of freedom, empirical validation, opinion scale, opinion dynamics

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Authors: Gagik Ayvazyan, Levon Hakhoyan, Surik Khudaverdyan, Laura Lakhoyan

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Black Si (b-Si) is a nano-structured Si surface formed by a self-organized, maskless process with needle-like surfaces discernible by their black color. The combination of low reflectivity and the semi-conductive properties of Si found in b-Si make it a prime candidate for application in solar cells as an antireflection surface. However, surface recombination losses significantly reduce the efficiency of b-Si solar cells. Surface passivation using suitable dielectric films can minimize these losses. Nowadays some works have demonstrated that excellent passivation of b-Si nanostructures can be reached using Al₂O₃ films. However, the negative fixed charge present in Al₂O₃ films should provide good field effect passivation only for p- and p+-type Si surfaces. HfO2 thin films have not been practically tested for passivation of b-Si. HfO₂ could provide an alternative for n- and n+- type Si surface passivation since it has been shown to exhibit positive fixed charge. Using optical simulation by Finite-Difference Time Domain (FDTD) method, the possibility of b-Si passivation by HfO2 films has been analyzed. The FDTD modeling revealed that b-Si layers with HfO₂ films effectively suppress reflection in the wavelength range 400–1000 nm and across a wide range of incidence angles. The light-trapping performance primarily depends on geometry of the needles and film thickness. With the decrease of periodicity and increase of height of the needles, the reflectance decrease significantly, and the absorption increases significantly. Increase in thickness results in an even greater decrease in the calculated reflection coefficient of model structures and, consequently, to an improvement in the antireflection characteristics in the visible range. The excellent surface passivation and low reflectance results prove the potential of using the combination of the b-Si surface and the HfO₂ film for solar cells applications.

Keywords: antireflection, black silicon, HfO₂, passivation, simulation, solar cell

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Authors: Rocio López, Miriam Tena, Montserrat Pérez, Rosario Solera

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Biotransformation of organic waste into biogas is considered an interesting alternative for the production of clean energy from renewable sources by reducing the volume and organic content of waste Anaerobic digestion is considered one of the most efficient technologies to transform waste into fertilizer and biogas in order to obtain electrical energy or biofuel within the concept of the circular economy. Currently, three types of anaerobic processes have been developed on a commercial scale: (1) single-stage process where sludge bioconversion is completed in a single chamber, (2) two-stage process where the acidogenic and methanogenic stages are separated into two chambers and, finally, (3) temperature-phase sequencing (TPAD) process that combines a thermophilic pretreatment unit prior to mesophilic anaerobic digestion. Two-stage processes can provide hydrogen and methane with easier control of the first and second stage conditions producing higher total energy recovery and substrate degradation than single-stage processes. On the other hand, co-digestion is the simultaneous anaerobic digestion of a mixture of two or more substrates. The technology is similar to anaerobic digestion but is a more attractive option as it produces increased methane yields due to the positive synergism of the mixtures in the digestion medium thus increasing the economic viability of biogas plants. The present study focuses on the energy recovery by anaerobic co-digestion of sewage sludge and waste from the aquaculture-fishing sector. The valorization is approached through the application of a temperature sequential phase process or TPAD technology (Temperature - Phased Anaerobic Digestion). Moreover, two-phase of microorganisms is considered. Thus, the selected process allows the development of a thermophilic acidogenic phase followed by a mesophilic methanogenic phase to obtain hydrogen (H₂) in the first stage and methane (CH₄) in the second stage. The combination of these technologies makes it possible to unify all the advantages of these anaerobic digestion processes individually. To achieve these objectives, a sequential study has been carried out in which the biochemical potential of hydrogen (BHP) is tested followed by a BMP test, which will allow checking the feasibility of the two-stage process. The best results obtained were high total and soluble COD yields (59.8% and 82.67%, respectively) as well as H₂ production rates of 12LH₂/kg SVadded and methane of 28.76 L CH₄/kg SVadded for TPAD.

Keywords: anaerobic co-digestion, TPAD, two-phase, BHP, BMP, sewage sludge, fish waste

Procedia PDF Downloads 156