Search

The injection of seawater into a hydrocarbon reservoir (seawater flooding), as an oil recovery method, triggers microbial reservoir souring, through which microorganisms consume sulfate ions and produce hydrogen sulfide, which is hazardous, corrosive, and detrimental to the environment if enters production wells. A strategy to mitigate this problem is to add nitrate or nitrite to the injection seawater, also known as nitrate or nitrite treatment. This study investigates nitrate treatment in a simulated real-world sector scale hydrocarbon reservoir in the Danish North Sea through a non-isothermal multi-phase multi-component bio-chemical model and field observations. The common expectation is that the higher the concentration of nitrate or nitrite in the injection seawater the less hydrogen sulfide production. However, the results of this study show that slowing down the microorganisms (or mitigation through nitrate treatment) may cause higher hydrogen sulfide production from production wells. Put differently, not only the total amount of hydrogen sulfide generated inside the reservoir matters, but also the location of the generation zone and its distance from production wells matter. Therefore, it is possible that insufficient amounts of nitrate cause the generation zone to move toward the production wells. Hence, more hydrogen sulfide is produced during the lifetime of the reservoir. Moreover, considering laboratory and field scale measurements, in the presence of coupled multi-physics processes, the growth rates at the field scale are significantly lower than those observed in the laboratory experiments, under in-situ conditions, utilizing actual reservoir fluid samples.

Purpose Design of small disc-type permanent magnet (PM) brushed DC motors for servomechanisms is challenging. The purpose of this paper is to propose a special coreless double-sided structure. This easy to manufacture motor has two set of shifted concentrated windings on both sides of the rotor. All of the coils in each winding are simply connected in series. A simple arcless commutator, which shares the features of both the usual commutators and slip rings, is connected to each winding at only two points. Design/methodology/approach By replacing the PMs with an equivalent current density, main design equations of the motor have been derived through the solving of scalar Poisson equation. A radial division technique has been used to take the radial variations into account. This provides the ability of considering various shapes of coils and PMs. A novel iterative algorithm has been proposed to design a motor with high torque capability, compared to other coreless counterparts. Some design variables are obtained based on an independent optimization problem, which maximizes the active portion of windings. The other variables are calculated in such a way that the design requirements are satisfied. Findings The feasibility and capability of the new structure have been proved by prototyping a sample motor. Comparing the design outputs with the results of the 3D finite element analysis and experimental tests shows a good agreement. This verifies the accuracy of the proposed design method. Originality/value A new structure for PM brushed DC motors and a novel algorithm for its design has been developed.

An increasing number of wildfire disasters occurred in recent years in the U.S. Here, we demonstrate that cumulative primary human exposure – population residing within large wildfires’ perimeters – was 594,850 people from 2000-2019 across the Contiguous U.S. (CONUS), 82% of which occurred in the Western U.S. Primary population exposure increased by 125% in CONUS in the past two decades, noting large uncertainty ranges. We show that population dynamics from 2000-2019 alone accounted for 24% of the observed increase rate in human exposure, whereas increased wildfire extent drove a majority of the observed trends. Additionally, we document widespread exposure of roads (412,155 km) and transmission powerlines (14,835 km) to large wildfires in CONUS, with an increased rate of 58% and 70% from 2000-2019, respectively. Our findings highlight the benefits of mitigation and adaptation efforts to help societies cope with wildfires.

Shared socio-economic pathways (SSP) scenario analysis is concerned with developing climate change adaptation strategies that perform well across a wide range of plausible future socio-economic and climate change conditions. However, downscaled/localized SSP scenarios, most relevant for regional climate adaptation, are poorly understood in terms of their deep uncertainties and how these scenarios can contribute to the development of robust regional policies in coupled human-water systems. In the present study, we propose a new framework that integrates a multi-scenario multi-objective (meta-criteria) optimization analysis of a set of downscaled/localized SSP storylines with the robust decision-making concept to find optimal robust solutions under deep uncertainty concerning regional climate adaptation. By developing an integrated dynamic simulation-optimization model, potential policy alternatives are investigated, and their robustness evaluated based on four key objectives: farm income, groundwater depletion, soil salinity, and reliability. Scenario-based multi-objective optimization for multiple SSP scenarios is merged into a robust optimization problem and evaluated in parallel. The proposed framework is applied to study potential robust solutions for vulnerabilities of a real-world human-water system in Pakistan's Rechna Doab region that has multiple stakeholders and conflicting objectives. The results revealed Pareto optimal solutions that are both optimally feasible and robustly efficient. The socio-environmental conditions of SSPs have a significant influence on the estimated robustness. The candidate solutions under scenario SSP1 are remarkably comparable to those offered by scenario SSP5, which was deemed to be the best among the SSPs evaluated. SSP3 was the least desirable of the SSP scenarios examined and solutions resulted in undesirable soil salinity, groundwater depletion, and reliability values. By incorporating SSP narratives and quantitative scenario analysis, the proposed framework revealed advantages for integrated dynamic modelling of human-water systems with a high level of uncertainty and complex interconnections to discover robust climate change adaptation solutions.

This article proposes a method to design a three-stage induction coilgun system using the finite-element method (FEM). The system is designed to launch a 21.5 kg projectile. The method which is used to calculate the mutual inductance and the mutual inductance gradient between the two coils is expressed. Furthermore, the variation of mutual inductance and its gradient with respect to the distance between the two coils is indicated. The system parameters (i.e., coil currents, mutual inductance, mutual inductance gradient, force, velocity, and magnetic field distribution) are calculated and analyzed utilizing ANSYS Maxwell software. To verify the performance of the initial design, its analytical model is developed and validated in MATLAB software. The results of the analytical model are compared with the results obtained from the FEM method, and it is shown that they are well-matched in all waveforms. Besides, the efficiency of the system is improved through optimization by applying a genetic algorithm (GA). In this way, the efficiency of the system is enhanced from 29% to 36.6% and also the muzzle velocity is increased from 128 to 143 m/s. This method can be used to design a large-scale multistage induction coilgun (MSIC) for launching massive projectiles and reach high velocities.

Water Distribution System (WDS) are strategic infrastructures in all countries. In recent decades, several optimization-based frameworks have been developed to detect potential contaminant events through risk mitigation strategies using the optimal placement of water quality sensors. However, outcomes of the optimization models may not sufficiently represent the priorities of involved stakeholders in real-world case studies where conflicts of interest arise. Therefore, conflict resolution frameworks that consider stakeholder engagement are needed to enhance the security of a WDS through an agreed-upon layout of an optimal number of sensors. In this study, according to the uncertain nature of input contamination into the network, a Fuzzy Transformation Method (FTM) and a Monte-Carlo Simulation (MCS) were employed to address uncertainties in the EPANET simulation model. A fuzzy-based NSGA-II optimization model was developed to determine trade-offs among targets of stakeholders. Social Choice Theories (SCTs) was used to specify the compromise solutions on each trade-off curve. Using the possibility degree method, the obtained fuzzy intervals were ranked based on each stakeholder’s point of view. Finally, the most appropriate SCTs were introduced through a negotiation method (unanimity fallback bargaining) at each confidence level. The application of the proposed methodology was evaluated in the WDS of the city of Lamerd in Fars, Iran. The capability of the proposed methodology in selecting socio-optimal sensor placement was compared with the results of previous studies. The obtained results demonstrated that the proposed framework yielded a reliable outcome and enhance the decision-making condition for stakeholders to improve the security of a WDS.

The dummy load is an essential part of Loran transmitter whose role is paramount in local positioning applications. The duty of the dummy load is to provide the equivalent impedance of the antenna to connect to the Loran transmitter when the antenna is disconnected. For the realization of the dummy load with specified impedance values, the inductance of the self-loading section is designed precisely. In this regard, this paper deals with inductance matrix and equivalent inductance calculations, corresponding to stranded and solid cables. Inductance matrix components, consisting of mutual and self-inductance, are calculated analytically and then are validated by the finite element method (FEM). The divergence of analytical calculations from FEM results is investigated as coil pitch changes. In addition to inductance, parasitic capacitances will be taken into consideration to determine the equivalent circuit of Loran transmitter inductor. With regard to the calculated inductance matrix and parasitic capacitances, the ladder equivalent circuit of the inductor will be presented.

In this paper, a double-layer half-cycle generator (HCG) has been designed and built. The proposed HCG creates sinusoidal flow with 400 A peak and 5 µs pulse width which feeds RLC load with 100 kHz work frequency, within resonance mode. Previous HCGs have been designed based on saturable reactor (SR). It should be noted that SR is a nonlinear element, and it will be distanced from its desirable performance upon change of temperature and under impact; however, a double-layer HCG has been proposed with no such defects. In proposed HCG, thyristor has been used instead of SR which is controllable, and it has none of aforementioned problems. Also, when SR is eliminated, its reverse retrieval needs no minority carriers. This way, sweep-out circuit may be also eliminated. From among other advantages of proposed HCG, reduction in number of circuit layers may be referred to, comparing to previous HCG. This results in reduction in number of equipment which in turn optimizes proposed HCG, in terms of volume and manufacturing costs. Finally, proposed HCG has been simulated in Matlab, while it has been implemented practically. Comparing simulation results and laboratory sample confirms correctness of relationships, in analytical design of HCG.

In this paper, a waveguide consisting of a core of As2Se3 chalcogenide glass and the upper and lower claddings of MgF2 with two zero-dispersion wavelengths (ZDW) has been proposed. By optimization of the dimensions of the core and the claddings, their effects on the dispersion curve have been investigated and a suitable structure with a flat dispersion curve, an effective mode area of ​​1.6 μm2 in a pump wavelength of 2.8 μm, and hence, a nonlinear coefficient greater than 34 w−1 m−1 has been obtained. A broadband supercontinuum in a wavelength range of 1.5 μm to 15 μm has been generated by applying an input pulse with duration of 100 fs and a maximum power of 2 kw to this waveguide. Due to the large width of the supercontinuum generated (SCG), the short length of the waveguide (maximum 5 mm), and a low input power, this structure is suitable for use in optical integrated circuits and its various applications.

Sedimentation ponds (SPs) are nature-based solutions (NBSs) for sustainable stormwater management. SPs control the quantity and quality of runoff and promote biodiversity. Hence, the optimal design of SPs is crucial for ecosystems resilience in urban and natural environments. This study aims to optimize the design of roadside SPs in terms of location and surface area, considering the resilience to stressors such as climate changes and pollution load variations. Accordingly, the highway runoff in a new 22 km highway (E18 Arendal-Tvedestrand) in southern Norway was simulated by the storm water management model (SWMM). The quantity and quality (BOD and TSS values) of highway runoff in all probable scenarios of existing uncertainties were estimated for potential outfall points using the repeated execution model of SWMM coded in MATLAB®. The scenarios were defined based on applying best management practices (BMPs), including grass swale and infiltration trench in different sections of the road that work before SPs, climatic (rainfall quantity estimated by the LARS-WG model), and modeling uncertainties (buildup and washoff coefficients). The generated dataset was then applied to assess the resilience of sedimentation ponds in potential outfalls to climate change and pollution load shocks. The resiliency was quantified for three metrics, including the quantity and quality of receiving runoff to sedimentation ponds and biodiversity in ponds over 25 years (2020-2045). The biodiversity index was defined based on Shannon's Entropy computed from field observation in 12 highway sedimentation ponds across Norway. Using this procedure, it was determined that the proper arrangement of BMPs along the road and the optimal design of ponds enhance the resilience of SPs by 40% over time. This study makes important contributions to stormwater management, the resilient design of NBS, and achieving UN SDG6 (Clean water and sanitation).

In this paper, with dispersion engineering, two waveguides with silicon core and SiO2 cladding are proposed to generation the supercontinuum spectrum and optical frequency combs. By injecting a pulse with a peak power of 800 (W) and a pulse duration of 50 (fs), the output supercontinuum spectrum is obtained from a wavelength of 1100 (nm) to 4000 (nm). Also, by applying a maximum power of 1 KW and a pulse width of 100 (fs), optical frequency combs based on a supercontinuum with a broadband frequency combs have been obtained. Our proposed structure has good potential for engineering and achieving flatness dispersion which there are two zero dispersion wavelengths at 1890 (nm) and 2850 (nm). This flat dispersion can be very useful to achieve the desired output spectrum. Due to the materials used and the flat structure of the proposed waveguides, these waveguides can be used for integrated optical circuits as well as applications in optical communications, spectroscopy, and sensors.

Hydrogen storage is a key component in realization of an emission free future. Depleted hydrocarbon reservoirs offer a low cost medium for large-scale hydrogen storage. While the effect of hydrogen in triggering some chemical and biochemical reactions has stablished some screening criteria to choose a suitable underground storage site according to reservoir geochemistry, there is no screening criteria based on the effect of variables such as pressure, temperature and composition of the residual hydrocarbon on hydrogen recovery. In this work, we first investigate the cost required for hydrogen compression in terms of the work required for compressors. Then we investigate the effect of reservoir pressure, storage pressure, reservoir temperature and residual composition on hydrogen recovery. Our results show that on one hand the work required for pressurizing hydrogen does not increase linearly with pressure, and on the other hand, hydrogen recovery increases with storage pressure. Additionally, Hydrogen recovery was shown to decrease by increase in reservoir initial pressure before hydrogen storage. Therefore, it seems that hydrogen storage will be more efficient if it is conducted at the highest possible pressure in a reservoir with low initial pressure (either a shallow reservoir, or a depleted reservoir). Our results did not show any strong relationship between hydrogen recovery and temperature. Hydrogen recovery showed to increase slightly with increase in residual hydrocarbon density. However, the effect of residual hydrocarbon was observed to be significant on purity of the produced hydrogen. In this sense, depleted black oil reservoirs seem to be the best and dry gas reservoirs the worst choice.

In this study, a new DC–DC single-input–dual-output (SIDO) converter is proposed which is able to step up and share the input voltage between the output terminals with constant duty cycle for whole ranges of duty cycles. Due to the fact that the voltage stresses on the semiconductors of the proposed converter are considerably low, the proposed converter can be applied in both low- and high-power applications. This topology can be used instead of two boost converters, which have very improved conversion ratios in comparison with the recently presented step-up converters. The proposed configuration can be used in many applications such as renewable energy sources and diode-clamped inverter in the grid-tied systems. In this paper, steady-state and small-signal analyses of the SIDO converter are presented and the simulation and experimental results are extracted and compared. In practical applications that SIDO is needed, using single-input–single-output can be a solution, resulting high cost. To reduce the costs, this study proposes a novel topology, which has reduced components and can step up the input voltage into two separate ports. Finally, a prototype circuit with 42 V input and 510 V/372 W and 730 V/381 W outputs are built to validate the theoretical analysis.

This article intends to design, simulate, and implement a dummy load coil, a very significant element, in the Loran transmitter system. In order to ensure the impedance matching, the solenoid coil is designed with an inductance range from 200 to 300 $\mu \text{H}$ . Analytical and finite-element methods are deployed as the most common practice solutions to calculate and simulate the coil inductance. The results obtained from these two methods are compared, and their accuracy and effectiveness are analyzed based on the experimentally implemented coil. Furthermore, a new method is devised to calculate the inductance of the solenoid coil containing numerous wire strands.

A magnetohydrodynamic (MHD) thruster is a type of electric motors which moves electrically conductive fluids without any mechanical moving parts. In this study, a linear-type MHD thruster is compared with a helical-type MHD thruster that has the same channel length and volume. For this purpose, two analytical models are used to predict the behaviors of these two types of marine MHD thrusters. The analytical model used for the helical thruster is validated by comparison to the experimental data obtained by other researchers. To validate the analytical model used for the linear thruster, a thruster prototype is manufactured and tested. The results show that although the solenoid magnet of the helical-type thruster is much easier to get a higher magnetic flux density than the saddle-shaped magnet of the linear-type thruster, the efficiency and propulsion force density of the linear-type thruster are much better than those of the helical-type one. Therefore, the linear-type thrusters cannot be ignored simply because of the complexity of their coils.

A new ripple base signal flow graph (R-SFG) modelling method was proposed to accurately model and analyse a family of switching DC–DC converter. The performance of some DC–DC converters such as single-inductor multi-output converters is dependent on inductor current ripples. This makes the conventional modelling methods cannot fully predict the overall behaviour of converter. From this family and in this study, a single-inductor dual-output (SIDO) boost/boost converter has been modelled based on proposed R-SFG method. The simplicity and systematic procedure presented in this work showed that the R-SFG could be a good alternative for modelling switching converter with complicated structures and with high inductor current ripple. In the new R-SFG method, the effects of inductor current ripple have been considered to develop the conventional signal flow graph modelling method. In this work, a comparative study between two modelling methods has been carried out in a SIDO converter. A step-by-step direct mathematical manipulation was used to calculate the DC–DC transfer function of SIDO converter. The experimental results were included to show the validity of the obtained models. The experimental results showed that the maximum R-SFG modelling error was about 5% over the wide range of inductor current ripple.

A magnetohydrodynamic (MHD) thruster is a type of electric motor which does not have mechanical moving parts and directly converts electrical energy into mechanical energy. In this paper, a multiphysics numerical simulation has been performed to investigate the phenomena occurred in the channel of marine MHD thrusters. In this simulation, all electric, magnetic, and fluid flow fields have been considered 3-D. For this purpose, a marine MHD thruster model with saddle-shaped coils is selected, and its dimensions are determined. Then, this thruster is simulated numerically, and its electromagnetic and fluid flow parameters are studied. In this simulation, the effects of seawater electrolysis and end loss are taken into account. An experimental setup is established to validate the results obtained from the numerical simulation. The results reveal that the nonuniformities of the electric and magnetic fields along the channel have a great impact on the performance of the thruster. Unlike the results obtained in the previous studies, it is shown that the velocity near the electrodes is higher than that near the sidewalls arisen from the higher electromagnetic force close to the electrodes.