Detailed Model Research Articles

Nonlinear Backstepping Control of Grid-Forming Converters in Presence of Grid-Following Converters and Synchronous Generators

Grids in near future are going to host synchronous generators (SGs), legacy grid-following converters (GFLCs), and relatively new grid-forming converters (GFCs), where the latter two technologies support converter-interfaced generations. This change is going to introduce new challenges – one of them is the dc-link voltage collapse issue in GFCs following the outage of a generator. As a solution, this paper proposes a nonlinear backstepping control strategy that guarantees Lyapunov stability of a reduced-order model of such systems. To this end, first a reduced model of a 6-bus system with one GFC, one GFLC, and one SG is considered to develop fundamental understanding of such systems and derive a stabilizing control strategy. Then, based on certain observations, the simplified model is extended to a multimachine system, which in turn helps developing the nonlinear control strategy in presence of bounded uncertainties. Further, a dc-link voltage tracking control is introduced to ensure controllable frequency support from GFCs. The proposed controller is decentralized in nature and requires limited communication only if neighboring buses have GFCs and/or GFLCs. Detailed phasor models of the 6-bus system and the modified 68-bus New England-New York system with 2 GFCs and 2 GFLCs are used to demonstrate the effectiveness of the proposed control strategies.

New interpretation technique for tracer well tests

Background. Tracer well tests were proposed in the last century as an approach for elaboration of detailed reservoir models. Such tests implied injecting weakly adsorbable tracers into an injection well followed by collection and analysis of samples in nearby production wells. The results were assumed to clarify well connectivity and inter-well hydraulic conductivity. However, practical application of these tests showed that the tracer penetrates into the production well much faster than predicted from estimates of the reservoir properties.Aim. To develop a new technique for interpreting the results of tracer well tests.Materials and methods. The process of tracer movement along a self-induced hydraulic fracture was simulated taking into account the mass transfer parameter. The developed algorithm for interpreting the results of tracer studies was tested in a deposit located in Western Siberia. The productive interval is located in the Jurassic interval of the Vasyugan Formation. An aqueous solution of thiocarbamide with a concentration of 9% was used as a tracer. Injection was carried out through injection well XX74 for 3 h. The mass of the injected tracer was 1 t. Measurements in six reacting production wells XX72, XX73, XX75, XX76, XX77, and XX78 were conducted for 75 days. During this time period, 516 samples were collected. In the first three days, 36 samples were extracted at equal time intervals; in the following two weeks, 90 samples were extracted also at equal time intervals; during the remaining days, measurements were conducted 2—3 times per week for each well. The results of the conducted studies were interpreted based on the developed methodology for all the wells.Results. A numerical and analytical solution of the problem of tracer slug movement along the fracture was obtained. Account was taken of the mass transfer between the fluids and the layer, as well as the dissipation of the tracer slug. This solution was used as the basis for a new technique for interpreting the results of tracer well tests, which allows a greater number of fracture parameters to be determined.Conclusion. The developed technique for determining the parameters of technogenic fractures was applied in practice. The presence of several fractures connecting injection and production wells is shown. It is established that the process of formation of such fractures in the reservoir is still ongoing.

Structural Model Update on the Patuha geothermal system, West Java, Indonesia

The Patuha geothermal field is a steam-dominated geothermal system lying on a quaternary volcanic unit in West Java Province, Indonesia. The existence of manifestations in this field is interpreted from the structure control and rock deformation that generate steam production in reservoir zone. This updated study is aimed to further describe the geometry and kinematics of the geological structures model to estimate the permeable areas. The model also will explain the link between the larger tectonic framework and the detailed structure model scale in Patuha. The analysis consists of reassessment the LiDAR data, surface structure features measurement from fieldwork, and review the updated subsurface data such as feed zones, new borehole images, and re-visit the geophysical data such as microearthquakes and gravity. The surface structural interpretation is drawn from a larger area to understand the regional tectonic framework and the relation with small detail from faults and non-tectonic features. Later, the new structural framework from surface data is correlated with subsurface data that indicates permeable features, including feed zones and conductive fractures, then coupled with the geophysical data. The latter part, which concerns validating surface fault traces using subsurface data, is currently being developed and will be included in the subsequent paper. An integrated review of the geological structure of the lineament found that a strike-slip system developed in the larger Patuha area with the main fault trending NE-SW, while the accompanying fault is en-echelon faults trending relatively NNE-SSW.

Integrated climate, land, energy, and water framework to support the Nationally Determined Contribution updating process

System models help policymakers to produce net zero decarbonization pathways. In 2019, Costa Rica launched its National Decarbonization Plan (NDP) – constructed using a detailed Open-Source energy Modelling System (OSeMOSYS-CR) model and simplified ones for non-energy sectors. The country then developed an integrated Climate, Land, Energy and Water (CLEW) model to capture synergies across sectors and guide future climate related processes. This resulted in the CLEW-CR model. In 2020, the country updated its Nationally Determined Contributions (NDCs), deploying a highly participatory process supported by the CLEW-CR model to guide the discussions with over 150 stakeholders. This paper presents the framework adopted to develop the CLEW-CR model (from data collection to scenarios creation and cost-benefit analysis) and describes its use to align its NDCs with its NDP. Over 15 different scenarios were produced to inform the country's dialogue during the updating process of its NDCs demonstrating the flexibility of this model to support multiple policy questions. This paper shows that deploying the NDC by 2030 and the NDP by 2050 would result in a net economic benefit of $55 billion – about 85 % of Costa Rica's GDP, highlighting the economic viability of Costa Rica's commitment to a sustainable future.

Virtual Practice Teaching of Civics Classes in Colleges and Universities in the Context of Big Data Technology

Abstract In this study, we successfully realized the interaction design of virtual Civics teaching scene through multiresolution hierarchical detail (LOD) model, and constructed an immersive teaching environment using texture mapping technology. Combined with the gesture recognition and training of Adaboost classifier, this paper proposes an innovative interaction model for virtual Civics and Politics teaching. Through in-depth Analysis of the virtual interactive teaching elements of Civics courses in colleges and universities, this study conducted a covariance analysis of the aspects of creativity, critical thinking, metacognition, self-efficacy, and scientific ideological reasoning. Then it explored the effects of different places of origin and types of schools on the acceptance of virtual Civics courses by the students. It was found that among the science and engineering and teacher training students, the science and engineering students paid more attention to the virtual Civics teaching (3.36 and 3.05, respectively). In addition, compared with traditional Civics teaching, virtual practice teaching significantly increased students’ motivation (3.79), proving that Civics courses incorporating virtual interaction design have significant advantages in improving learning attractiveness.

Techno-economic-environmental analysis and fluid selection of transcritical organic Rankine cycle with zeotropic mixtures

Waste heat recovery is regarded as highly efficacious in ameliorating energy and environmental problems brought on by rapid economic and societal growth. The organic Rankine cycle (ORC), specifically transcritical ORC (tORC) garners significant attention for its potential in waste heat power generation. Researchers still seek to further improve performance for tORC, such as using zeotropic mixtures. Aimed at selecting the working fluid pairs that can bring better performance for tORC, this study provides a more comprehensive performance evaluation of tORC systems by developing a novel multi-attribute integrated assessment model that encompasses techno-economic-environmental aspects. To establish this model, the detailed mathematical models of the tORC are established first and used to obtain system performance indicators. Then, a refined analytic hierarchy process to assign weights to various performance indicators to complete the multi-attribute integrated assessment model. With the utilization of the proposed model, a thorough comparative analysis of the tORC system with ten groups of zeotropic mixtures is performed. Thus, the results of the working fluid selection can be obtained. Results show that R245fa/R600 and R600/R600a are more recommended than other working fluid pairs, with R600/R600a being the preferable choice when prioritizing environmental impact. While R245fa/R1234yf has the worst thermodynamic and environmental performance and R245fa/R227ea owns the worst economic performance. In conclusion, the findings show that employing a zeotropic mixture combines the benefits of the pure working fluids that comprise it. Compared to previous studies, this study provides a more comprehensive look at the selection of working fluids for tORC systems. It can offer valuable insights for selecting the appropriate working fluid more effectively for future applications.

The construction of an alternative fuel skeleton with a simplified n-heptane / 1-butene mechanism

Diesel is an important energy in the current world development. The promotion of industrial development has also brought serious drawbacks, energy depletion, and environmental pollution. Hence, the construction of new alternative diesel fuel has become an indispensable problem. Based on the detailed mechanism model of n-heptane and 1-butene, the simplified mechanism model of n-heptane and 1-butene was constructed by using oxidation path and temperature sensitivity analysis and various mechanism simplification methods. The experimental results show that the ignition delay of the simplified mechanism and the concentration of main components meet the experimental requirements. Coupled with the two simplified mechanisms, a diesel simplified framework containing 136 components and 746 primitive reactions was constructed. The HCCI ignition time was calculated for the diesel simplified framework. The simplified framework of diesel oil can predict the ignition time of HCCI with high precision under different temperature conditions. It can accurately describe the fuel combustion process.

Black Hole Ultracompact X-Ray Binaries as Galactic Low-frequency Gravitational Wave Sources: The He Star Channel

Black hole (BH) ultracompact X-ray binaries (UCXBs) are potential Galactic low-frequency gravitational wave (GW) sources. As an alternative channel, BH UCXBs can evolve from BH+He star binaries. In this work, we perform a detailed stellar evolution model for the formation and evolution of BH UCXBs evolving from the He star channel to diagnose their detectability as low-frequency GW sources. Our calculations found that some nascent BH+He star binaries after the common-envelope (CE) phase could evolve into UCXB-LISA sources with a maximum GW frequency of ∼5 mHz, which can be detected in a distance of 10 kpc (or 100 kpc). Once BH+He star systems become UCXBs through mass transfer, they would emit X-ray luminosities of ∼1038 erg s−1, making them ideal multimessenger objects. If the initial He-star masses are ≥0.7 M ⊙, those systems are likely to experience two Roche lobe overflows, and the X-ray luminosity can reach a maximum of 3.5 × 1039 erg s−1 in the second mass-transfer stage. The initial He-star masses and initial orbital periods of progenitors of Galactic BH UCXB-LISA sources are in the range of 0.32–2.9 M ⊙ and 0.02–0.19 days, respectively. Nearly all BH+He star binaries in the above parameter space can evolve into GW sources whose chirp masses can be accurately measured. Employing a population synthesis simulation, we predict the birthrate and detection number of Galactic BH UCXB-LISA sources evolving from the He star channel are R = 2.2 × 10−6 yr−1 and 33 for an optimistic CE parameter, respectively.

An experimental and chemical kinetic simulation study of the high-temperature pyrolysis of linear C1–C5 alcohols

The high-temperature pyrolysis characteristics of C1–C5 linear alcohols, including methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol, systematically studied experimentally and the results interpreted using a detailed kinetic model. Specifically, a single-pulse shock tube coupled to a gas chromatography-mass spectrometry (GC-MS) system and a gas chromatograph (GC) is used to conduct a comprehensive experimental study on the high-temperature pyrolysis of the five alcohols, at pressures of 5 and 10 bar, in the temperature range 1000–1800 K at 1% fuel diluted by argon. Qualitative and quantitative analyses are conducted on the reactant, intermediate, and product species involved to determine species distributions as a function of temperature. A detailed chemical kinetic mechanism, NUIGMech1.3, is used to simulate the experimental data under the working conditions. The simulation results are compared with the experimental results, and it is shown that the overall trends between experiments and model predictions are relatively ideal in the comparison of all product and reactant concentrations, even though there is still a phenomenon of inaccurate prediction. Reaction pathway analysis is then conducted on the five alcohols. The present work not only provides additional experimental data for alcohols, but also provides insights into the high-temperature pyrolysis characteristics of the five fuels, which will be valuable for further development and optimization of detailed kinetic mechanisms of these alcohols and promote their practical application.

A detailed computational modelling and analysis of the effect of geometric dimensions for coil assembly to transfer power wirelessly in electric vehicles

A detailed computational modelling and analysis of the effect of geometric dimensions for coil assembly to transfer power wirelessly in electric vehicles

From prediction to measurement, an efficient method for digital human model obtainment

Digital human has been increasingly used in industry, for example in Metaverse which has been a popular topic in recent years. The existing method of obtaining digital human models are either expensive or lack of accuracy. In this paper, we discuss a novel method to reconstruct a 3D human model from 2D images captured by a monocular camera. The input of our method only requires a set of rotated human body images that can accept slight movement. First, we apply a deep learning method to predict an initial 3D human body model from multi-view human body images. Then the total detailed digital human model will be computed and optimized. The typical method requires the human body and cameras fixed to obtain a visual hull from a significant number of camera images. This could be extremely expensive and inconvenient when such an application is developed for online users. Compared to the structural lighting measurement system, our predict-optimized framework only requires several input images captured by personal equipment to provide enough accuracy and online use resolution results.

Distributed Adaptive Robust Restoration Scheme of Cyber-Physical Active Distribution System With Voltage Control

The increasing penetration of distributed generators (DGs) and the advancement of information and communication technologies (ICTs) will facilitate the transformation of the traditional passive distribution network towards a cyber-physical active distribution system (CPADS). With the increasing risks of extreme events, such as natural disasters (e.g., flooding) and cyber-physical attacks, it is critical for CPADS to formulate a restoration scheme to improve its resilience. Therefore, in this paper, a distributed adaptive robust restoration scheme with voltage/var control is presented to cope with the high-impact but low-frequency events. First, a detailed cyber-physical system model is established, including the dynamic routing and the quality-of-services (QoS) in both optical fiber networks and 5G wireless networks. Then, the interactions between the cyber system and the physical system are analyzed. Based on the cyber-physical system model, a two-stage restoration scheme with voltage/var control is proposed by coordinately scheduling different network assets in day-ahead and in real-time. The formulated problem is solved by adaptive robust optimization (ARO). To further enhance the resilience of the CPADS, a distributed restoration framework is proposed. The distributed problem is solved by the alternating direction method of multipliers (ADMM) algorithm, and the convergence of the discrete problem is ensured by introducing the alternating optimization procedure (AOP). Considering the cyber faults, a boundary variable compensation and residual relaxation mechanism is proposed in ADMM. The proposed framework and methodology are verified in the case study. The convergence and the efficiency of the proposed algorithm are verified. Compared with the state-of-art works, the advantages in load restoration capability of the proposed method are shown.

Notice of Violation of IEEE Publication Principles: An Energy-Efficient Heterogeneous Memory Architecture for Future Dark Silicon Embedded Chip-Multiprocessors

Main memories play an important role in overall energy consumption of embedded systems. Using conventional memory technologies in future designs in nanoscale era causes a drastic increase in leakage power consumption and temperature-related problems. Emerging non-volatile memory (NVM) technologies offer many desirable characteristics such as near-zero leakage power, high density and non-volatility. They can significantly mitigate the issue of memory leakage power in future embedded chip-multiprocessor (eCMP) systems. However, they suffer from challenges such as limited write endurance and high write energy consumption which restrict them for adoption in modern memory systems. In this article, we present a convex optimization model to design a 3D stacked hybrid memory architecture in order to minimize the future embedded systems energy consumption in the dark silicon era. This proposed approach satisfies endurance constraint in order to design a reliable memory system. Our convex model optimizes numbers and placement of eDRAM and STT-RAM memory banks on the memory layer to exploit the advantages of both technologies in future eCMPs. Energy consumption, the main challenge in the dark silicon era, is represented as a major target in this work and it is minimized by the detailed optimization model in order to design a dark silicon aware 3D Chip-Multiprocessor. Experimental results show that in comparison with the Baseline memory design, the proposed architecture improves the energy consumption and performance of the 3D CMP on average about 61.33 and 9 percent respectively.

Is there a black hole in the center of the Sun?

There is probably not a black hole in the center of the Sun. Despite this detail, our goal in this work to convince the reader that this question is interesting and that work studying stars with central black holes is well motivated. If primordial black holes exist then they may exist in sufficiently large numbers to explain the dark matter in the universe. While primordial black holes may form at almost any mass, the asteroid-mass window between 10−16−10−10M⊙\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$10^{-16} - 10^{-10}\\ \ extrm{M}_{\\odot }$\\end{document} remains a viable dark matter candidate and these black holes could be captured by stars upon formation. Such a star, partially powered by accretion luminosity from a microscopic black hole in its core, has been called a ‘Hawking star.’ Stellar evolution of Hawking stars is highly nontrivial and requires detailed stellar evolution models, which were developed in our recent work. We present here full evolutionary models of solar mass Hawking stars using two accretion schemes: one with a constant radiative efficiency, and one that is new in this work that uses an adaptive radiative efficiency to model the effects of photon trapping.

Kinetic Modeling of Hepatic Metabolism and Simulation of Treatment Effects.

Mathematical modeling is a promising strategy to fill the experimentally unapproachable knowledge gaps about the relative contribution of various molecular processes to cellular metabolic function. To this end, we developed detailed kinetic models of the central metabolism of different cell types, comprising multiple metabolic functionalities. We used the model to simulate metabolic changes in several cell types under different experimental settings in health and disease. In this way, we show that it is possible to decipher and characterize the relative influence of various metabolic pathways and enzymes to overall metabolic performance and phenotype.Quantitative Systems Metabolism (QSM™) allows quantitative assessment of metabolic functionality and metabolic profiling based on proteomic data. Here, we describe the technique, namely, molecular resolved kinetic modeling, underlying QSM™. We explain the necessary steps for the generation of cell-specific models to functionally interpret proteomic data and point out some unresolved challenges and open questions.

Analysis of Hail Production via Simulated Hailstone Trajectories in the 29 May 2012 Kingfisher, Oklahoma, Supercell

Abstract This study uses a new, unique dataset created by combining multi-Doppler radar wind and reflectivity analysis, diabatic Lagrangian analysis (DLA) retrievals of temperature and water substance, and a complex hail trajectory model to create millions of numerically simulated hail trajectories in the Kingfisher, Oklahoma, supercell on 29 May 2012. The DLA output variables are used to obtain a realistic, 4D depiction of the storm’s thermal and hydrometeor structure as required input to the detailed hail growth trajectory model. Hail embryos are initialized in the hail growth module every 3 min of the radar analysis period (2251–0000 UTC) to produce over 2.7 million hail trajectories. A spatial integration technique considering all trajectories is used to identify locations within the supercell where melted particles and subsevere and severe hailstones reside in their lowest and highest concentrations. It is found that hailstones are more likely to reside for longer periods closer to the downshear updraft within the midlevel mesocyclone in a region of decelerated midlevel mesocyclonic horizontal flow, termed the downshear deceleration zone (DDZ). Additionally, clusters of trajectories are analyzed using a trajectory clustering method. Trajectory clusters show there are many trajectory pathways that result in hailstones ≥ 4.5 cm, including trajectories that begin upshear of the updraft away from ideal growth conditions and trajectories that grow within the DDZ. There are also trajectory clusters with similar shapes that experience widely different environmental and hailstone characteristics along the trajectory. Significance Statement The purpose of this study is to understand how hail grew in a thunderstorm that was observed by numerous instruments. The observations were input into a hail trajectory model to simulate hail growth. We found a part of the storm near the updraft where hailstones could remain aloft longer and therefore grow larger. Most modeled severe hailstones were found in the storm in this region. However, we also found that there are many different pathways hailstones can take to become large, although there are still some common characteristics among the pathways.

Does green mean clean? Volatile organic emissions from regular versus green cleaning products.

Cleaning products emit a range of volatile organic compounds (VOCs), including some which are hazardous or can undergo chemical transformations to generate harmful secondary pollutants. In recent years, "green" cleaners have become increasingly popular, with an implicit assumption that these are better for our health and/or the environment. However, there is no strong evidence to suggest that they are better for indoor air quality compared to regular products. In this study, the VOC composition of 10 regular and 13 green cleaners was examined by headspace analysis. Monoterpenes were the most prevalent VOCs, with average total monoterpene concentrations of 8.6 and 25.0 mg L-1 for regular and green cleaners, respectively. Speciated monoterpene emissions were applied to a detailed chemical model to investigate the indoor air chemistry following a typical cleaning event. Green cleaners generally emitted more monoterpenes than regular cleaners, resulting in larger increases in harmful secondary pollutant concentrations following use, such as formaldehyde (up to 7%) and PAN species (up to 6%). However, emissions of the most reactive monoterpenes (α-terpinene, terpinolene and α-phellandrene), were observed more frequently from regular cleaners, resulting in a disproportionately large impact on the concentrations of radical species and secondary pollutants that were formed after cleaning occurred.

Development of a surrogate artificial neural network for microkinetic modeling: case study with methanol synthesis

Speeding up microkinetic modeling by a surrogate artificial neural network.

Pre-supernova feedback sets the star cluster mass function to a power law and reduces the cluster formation efficiency

Context. The star cluster initial mass function is observed to have an inverse power law exponent around 2, yet there is no consensus on what determines this distribution, and why some variation is observed in different galaxies. Furthermore, the cluster formation efficiency (CFE) covers a range of values, particularly when considering different environments. These clusters are often used to empirically constrain star formation and as fundamental units for stellar feedback models. Detailed galaxy models must therefore accurately capture the basic properties of observed clusters to be considered predictive. Aims. We study how feedback mechanisms acting on different timescales and with different energy budgets affect the star cluster mass function and CFE. Methods. We use hydrodynamical simulations of a dwarf galaxy as a laboratory to study star cluster formation. We test different combinations of stellar feedback mechanisms, including stellar winds, ionizing radiation, and supernovae (SNe). Results. Each feedback mechanism affects the CFE and cluster mass function. Increasing the feedback budget by combining the different types of feedback decreases the CFE by reducing the number of massive clusters. Ionizing radiation is found to be especially influential. This effect depends on the timing of feedback initiation, as shown by comparing early and late feedback. Early feedback occurs from ionizing radiation and stellar winds with onset immediately after a massive star is formed. Late feedback occurs when energy injection only starts after the main-sequence lifetime of the most massive SN progenitor, a timing that is further influenced by the choice of the most massive SN progenitor. Late feedback alone results in a broad, flat mass function, approaching a log-normal shape in the complete absence of feedback. Early feedback, on the other hand, produces a power-law cluster mass function with lower CFE, albeit with a steeper slope than that usually observed.

Features of localization of remaining oil in terrigenous reservoirs and potential for their recovery at the final stage of field development

The paper considers one of the unique fields in terms of geological reserves. The paper also analyzes the development of the D3ps formation sections of the Devonian terrigenous layer of the studied field. A detailed geological and hydrodynamic model was constructed based on the consolidation of all available information. An integrated analysis of actual well performance data, field geophysical tests, geological and technical measures, results of infill drilling, as well as geological and hydrodynamic modeling confirmed the localization of reserves primarily in the upper bed of D3ps.1. The analysis of all performed studies revealed higher values of current oil saturation in the upper bed – up to 0.8 unit fractions and lower values in the lower bed – up to 0.68 unit fractions. Similar results were obtained from 87 sidetracks. Drilling of wells and sidetracks is proposed in areas with no well stock. Despite the final stage and high degree of field development, the proposed strategy will support oil production levels, increase remaining recoverable reserves, increase the efficiency of reserve recovery and improve the economic performance of field development. The introduction of modern development technologies, approaches to the analysis and monitoring of development will increase the target value of the final recovery factor from 0.608 to 0.613 unit fractions, which, with a significant amount of in-place reserves, made it possible to increase the remaining recoverable reserves by 35%. The strategy will make it possible to achieve higher oil recovery rates. The approaches used to solve the tasks set in the study can be applied to the fields of the Volga region.