This article presents the design, construction and field test of an experimental prototype of a low-cost hydrokinetic turbine technology made of local materials and e-waste components. The aim of this study is to investigate the performance of the turbine when subjected to field conditions in low flow velocity rivers. The research and development (R&D) involve the use of e-waste boat motor and locally available materials to develop a modular hydrokinetic turbine for generation of electricity using kinetic energy of rivers. A decommissioned boat motor with a 0.24 m diameter rotor is operated as a turbine. A shroud for flow acceleration was developed from 1.5 mm thick stainless-steel plates and a support structure constructed using angle lines. The field test results of the prototype generated about 11.543 ± 0.021 W and 37.129 ± 0.021 W or (equivalent of 0.011543 kWh and 0.037129 kWh) when operated at an approach flow velocity of 0.8 m s ^−1 and 1.2 m s ^−1 respectively. The wire to water ratio was determined instead of the C _p and the turbine achieved an overall wire to water efficiency of 0.99 and 0.95 respectively. This prototype technology can sustainably provide 24 h energy, sufficient to charge batteries in the rural areas and also provide opportunities within the community such as mobile charging points. An upscaled version of this low-cost technology can be adaptable in rural off-grid communities to enhance the access to electricity in developing countries.
<p>A novel disaggregation algorithm for commercial microwave links (CMLs), named CLEAR (CML Segments with Equal Amounts of Rain), is proposed. CLEAR utilizes a multiplicative random cascade generator to control the splitting of link segments, with the generator's standard deviation dependent on the rain rate and segment length. Spatial consistency during the splitting process is maintained using rain rate information from neighboring CMLs. CLEAR is evaluated on a network of 77 CMLs in Prague. The performance is assessed first using simulated rainfall fields and second through a case study with real attenuation data from the network to demonstrate its applicability in real-world scenarios. Results from the virtual rainfall fields indicate good overall performance, including the generation of realistic spatial patterns and effective estimation of maximal and minimal rain rates along CML paths. The stochastic nature of CLEAR allows it to represent uncertainty as an ensemble of rain rate distributions along CML paths. However, the generated ensembles significantly underestimate overall variability along the paths. Additionally, the case study on real data highlights challenges associated with uncertainties in CML quantitative precipitation estimates, which are common across all methods. In conclusion, CLEAR contributes to generating more representative rainfall distributions along CMLs, which is critical for spatial reconstruction of rainfall fields from path-integrated CML data. It also has the potential to reduce errors in CML quantitative precipitation estimates caused by assuming uniform rain rates along CML paths.</p>
Iliya Iliev, Andrey Kryukov, Konstantin Suslov
et al.
The paper addresses the issues of electromagnetic safety in traction networks of 25 kV AC railways. The purpose of the research is to develop digital models to determine the strengths of electromagnetic fields (EMFs) created by traction networks near portal-type metal structures. Such a structure in this study is represented by an overpass located above the tracks. The presence of a conductive structure significantly complicates the picture of EMF distribution in space. In contrast to the plane-parallel EMF of the traction network on interstation tracks in the spans between the supports of the catenary system, the field in this situation becomes three-dimensional. The technology for detecting strength relies on the concept of segments of limited length conductors, some of which may be buried. In order to apply the quasi-stationary zone equations to frequencies of up to 2000 Hz, it is essential to ensure that the size of the set of objects composed of these conductors does not exceed several hundred meters. Based on the modeling results, the dependences of the amplitudes and components of EMF strengths on the z-coordinate passing along the axis of the railway were obtained. In addition, three-dimensional diagrams were constructed to analyze the distribution of EMF in space. The findings of the studies show that the presented technique allows considering the influence of metal structures when modeling the electromagnetic fields of traction networks. It can be used in practice to develop effective measures to enhance electromagnetic safety conditions.
This chapter provides an overview of the application of hydraulics to flood hazard mapping in Japan. It explains the methods used to produce two types of flood hazard maps and highlights issues for further investigation, such as how to incorporate the process of levee collapse expansion in the vertical direction into modeling. It also provides evidence that flood hazard mapping is reliable in elucidating potential harm. Furthermore, it identifies problems with evacuation despite the provision of flood hazard maps. The purpose is to share information and serve as a call for new developments in flood hazard mapping. The information provided in this chapter can help young researchers and engineers to get a quick start in flood hazard mapping. At the same time, it can serve as an inspiration for more experienced researchers to pursue further in-depth studies.
Simulating 2D flow in fractured crystalline rock requires 2D stochastic discrete-fracture matrix (DFM) models. To obtain the simulation statistics of interest at an affordable computational cost, we aim to use the multilevel Monte Carlo method. To use this multiscale approach, one needs to upscale the hydraulic conductivity of the fractures by numerical homogenization. In this work, we substitute numerical homogenization with a surrogate model to speed up the computations. In particular, we resort to a deep convolutional neural network (CNN) connected to a deep feed-forward neural network. The equivalent hydraulic conductivity tensor $K_{eq}$ is predicted based on an input spatial random field (SRF) of hydraulic conductivity tensors, cross-section, and hydraulic conductivity of fractures. Three independent surrogates with the same architecture are trained using data from DFM models with three different ratios of hydraulic conductivities of fracture and bulk $K_f/K_b$. As the $K_f/K_b$ ratio increases, the multivariate $K_{eq}$ distribution becomes more complex, and thus, the prediction accuracy of the trained surrogates deteriorates. Regardless of $K_f/K_b$, however, an improvement in the prediction accuracy of the trained surrogates is noted as the considered fracture density of the modeling setup decreases. We also investigate prediction accuracy on input SRFs of different correlation lengths. Upscaling by numerical homogenization and by surrogate modeling is compared on two practical problems: upscaling of the hydraulic conductivity tensor and groundwater flow through a given surface. We obtained equally accurate results for the equivalent hydraulic tensor calculation of upscaled DFM models regardless of the upscaling method. For the groundwater flow problem, the accuracy of quantity of interest imitates the accuracy of $K_{eq}$ predictions.
Zhiyu Zhang, Chenkaixiang Lu, Wenchong Tian
et al.
Physics-based models are computationally time-consuming and infeasible for real-time scenarios of urban drainage networks, and a surrogate model is needed to accelerate the online predictive modelling. Fully-connected neural networks (NNs) are potential surrogate models, but may suffer from low interpretability and efficiency in fitting complex targets. Owing to the state-of-the-art modelling power of graph neural networks (GNNs) and their match with urban drainage networks in the graph structure, this work proposes a GNN-based surrogate of the flow routing model for the hydraulic prediction problem of drainage networks, which regards recent hydraulic states as initial conditions, and future runoff and control policy as boundary conditions. To incorporate hydraulic constraints and physical relationships into drainage modelling, physics-guided mechanisms are designed on top of the surrogate model to restrict the prediction variables with flow balance and flooding occurrence constraints. According to case results in a stormwater network, the GNN-based model is more cost-effective with better hydraulic prediction accuracy than the NN-based model after equal training epochs, and the designed mechanisms further limit prediction errors with interpretable domain knowledge. As the model structure adheres to the flow routing mechanisms and hydraulic constraints in urban drainage networks, it provides an interpretable and effective solution for data-driven surrogate modelling. Simultaneously, the surrogate model accelerates the predictive modelling of urban drainage networks for real-time use compared with the physics-based model.
Large Language Models (LLMs) are continuously being applied in a more diverse set of contexts. At their current state, however, even state-of-the-art LLMs such as Generative Pre-Trained Transformer 4 (GTP-4) have challenges when extracting information from real-world technical documentation without a heavy preprocessing. One such area with real-world technical documentation is telecommunications engineering, which could greatly benefit from domain-specific LLMs. The unique format and overall structure of telecommunications internal specifications differs greatly from standard English and thus it is evident that the application of out-of-the-box Natural Language Processing (NLP) tools is not a viable option. In this article, we outline the limitations of out-of-the-box NLP tools for processing technical information generated by telecommunications experts, and expand the concept of Technical Language Processing (TLP) to the telecommunication domain. Additionally, we explore the effect of domain-specific LLMs in the work of Specification Engineers, emphasizing the potential benefits of adopting domain-specific LLMs to speed up the training of experts in different telecommunications fields.
Advances in AI have led to new types of technical debt in software engineering projects. AI-based competition platforms face challenges due to rapid prototyping and a lack of adherence to software engineering principles by participants, resulting in technical debt. Additionally, organizers often lack methods to evaluate platform quality, impacting sustainability and maintainability. In this research, we identify and categorize types of technical debt in AI systems through a scoping review. We develop a questionnaire for assessing technical debt in AI competition platforms, categorizing debt into various types, such as algorithm, architectural, code, configuration, data etc. We introduce Accessibility Debt, specific to AI competition platforms, highlighting challenges participants face due to inadequate platform usability. Our framework for managing technical debt aims to improve the sustainability and effectiveness of these platforms, providing tools for researchers, organizers, and participants.
Two-dimensional free-surface flow over localised topography is examined with the emphasis on the stability of hydraulic-fall solutions. A Gaussian topography profile is assumed with a positive or negative amplitude modelling a bump or a dip, respectively. Steady hydraulic-fall solutions to the full incompressible, irrotational Euler equations are computed, and their linear and nonlinear stability is analysed by computing eigenspectra of the pertinent linearised operator and by solving an initial value problem. The computations are carried out numerically using a specially developed computational framework based on the finite element method. The Hamiltonian structure of the problem is demonstrated and stability is determined by computing eigenspectra of the pertinent linearised operator. It is found that a hydraulic-fall flow over a bump is spectrally stable. The corresponding flow over a dip is found to be linearly unstable. In the latter case, time-dependent simulations show that the flow ultimately settles into a time-periodic motion that corresponds to an invariant solution in an appropriately defined phase space. Physically, the solution consists of a localised large amplitude wave that pulsates above the dip while simultaneously emitting nonlinear cnoidal waves in the upstream direction and multi-harmonic linear waves in the downstream direction.
Technical efficiency indices (TEIs) can be estimated using the traditional stochastic frontier analysis approach, which yields relative indices that do not allow self-interpretations. In this paper, we introduce a single-step estimation procedure for TEIs that eliminates the need to identify best practices and avoids imposing restrictive hypotheses on the error term. The resulting indices are absolute and allow for individual interpretation. In our model, we estimate a distance function using the inverse coefficient of resource utilization, rather than treating it as unobservable. We employ a Tobit model with a translog distance function as our econometric framework. Applying this model to a sample of 19 airline companies from 2012 to 2021, we find that: (1) Absolute technical efficiency varies considerably between companies with medium-haul European airlines being technically the most efficient, while Asian airlines are the least efficient; (2) Our estimated TEIs are consistent with the observed data with a decline in efficiency especially during the Covid-19 crisis and Brexit period; (3) All airlines contained in our sample would be able to increase their average technical efficiency by 0.209% if they reduced their average kerosene consumption by 1%; (4) Total factor productivity (TFP) growth slowed between 2013 and 2019 due to a decrease in Disembodied Technical Change (DTC) and a small effect from Scale Economies (SE). Toward the end of our study period, TFP growth seemed increasingly driven by the SE effect, with a sharp decline in 2020 followed by an equally sharp recovery in 2021 for most airlines.
In the hydraulic fracturing of natural rocks, understanding and predicting crack penetrations into the neighboring layers is crucial and relevant in terms of cost-efficiency in engineering and environmental protection. This study constitutes a phase field framework to examine hydraulic fracture propagation in naturally-layered porous media. Biot's poroelasticity theory is used to couple the displacement and flow field, while a phase field method helps characterize fracture growth behavior. Additional fracture criteria are not required and fracture propagation is governed by the equation of phase field evolution. Thus, penetration criteria are not required when hydraulic fractures reach the material interfaces. The phase field method is implemented within a staggered scheme that sequentially solves the displacement, phase field, and fluid pressure. We consider the soft-to-stiff and the stiff-to-soft configurations, where the layer interface exhibits different inclination angles $θ$. Penetration, singly-deflected, and doubly-deflected fracture scenarios can be predicted by our simulations. In the soft-to-stiff configuration, $θ=0^\circ$ exhibits penetration or symmetrical doubly-deflected scenarios, and $θ=15^\circ$ exhibits singly-deflected or asymmetric doubly-deflected scenarios. Only the singly-deflected scenario is obtained for $θ=30^\circ$. In the stiff-to-soft configuration, only the penetration scenario is obtained with widening fractures when hydraulic fractures penetrate into the soft layer.
Srinivas Babu Pandi, Samia A. Binta, Savita Kaushal
Technical debt is a well-known challenge in software development, and its negative impact on software quality, maintainability, and performance is widely recognized. In recent years, artificial intelligence (AI) has proven to be a promising approach to assist in managing technical debt. This paper presents a comprehensive literature review of existing research on the use of AI powered tools for technical debt avoidance in software development. In this literature review we analyzed 15 related research papers which covers various AI-powered techniques, such as code analysis and review, automated testing, code refactoring, predictive maintenance, code generation, and code documentation, and explores their effectiveness in addressing technical debt. The review also discusses the benefits and challenges of using AI for technical debt management, provides insights into the current state of research, and highlights gaps and opportunities for future research. The findings of this review suggest that AI has the potential to significantly improve technical debt management in software development, and that existing research provides valuable insights into how AI can be leveraged to address technical debt effectively and efficiently. However, the review also highlights several challenges and limitations of current approaches, such as the need for high-quality data and ethical considerations and underscores the importance of further research to address these issues. The paper provides a comprehensive overview of the current state of research on AI for technical debt avoidance and offers practical guidance for software development teams seeking to leverage AI in their development processes to mitigate technical debt effectively
Balancing the management of technical debt within recommender systems requires effectively juggling the introduction of new features with the ongoing maintenance and enhancement of the current system. Within the realm of recommender systems, technical debt encompasses the trade-offs and expedient choices made during the development and upkeep of the recommendation system, which could potentially have adverse effects on its long-term performance, scalability, and maintainability. In this vision paper, our objective is to kickstart a research direction regarding Technical Debt in Recommender Systems. We identified 15 potential factors, along with detailed explanations outlining why it is advisable to consider them.
The purpose of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to outline experimental set up and the data collection process of an Acoustic Doppler Velocimeter (ADV) in a laboratory setting. The Nortek Vectrino ADV will be referenced in this CHETN as will the Nortek Comprehensive Manual for Velocimeters (Nortek AS 2018). Note that Nortek no longer sells the Vectrino, but the Vector, which is similar to the Vectrino aside from only having one configuration, is available.
Abstract Cities of North Africa experienced a long occupation up to the late 7th c. CE. Despite numerous studies on Late Antique urbanism, no systematic investigation of urban hydraulics has been carried out so far. This paper examines the hydraulic topography of three cities in the Byzantine period (ca. 6th c. CE): Leptis Magna (Tripolitania), Sbeitla (Byzacena), and Timgad (Numidia). This analysis assesses to what extent Late Antique societies managed the cities’ water supply by maintaining or transforming preexisting hydraulic networks. It considers the continuity of aqueducts and the reorganization of water networks, the state of hydraulic management and technology, and the perception of water resources. The hydraulic networks inherited from the Early Roman period were to some extent preserved, although greatly adapted to new concerns for security and new technical and environmental constraints, illustrating the resilience of Late Antique societies.
The Calcasieu Ship Channel (CSC) is a deep-draft federal channel located in southwest Louisiana. It is the channelized lowermost segment of the Calcasieu River, connecting Lake Charles to the Gulf of Mexico. With support from the Regional Sediment Management Program, the US Army Corps of Engineers, New Orleans District, requested that the US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, perform an investigation of the potential sources of sediment associated with dredging in the CSC. A previous study had quantified sediment from known sources, indicating that the known sediment sources contribute approximately only 21% of the volume that is regularly dredged from the channel. This technical report details the results of the current study, which employed multiple methods, including numerical analysis, to identify potential additional sources of sediment by first examining the available literature and the modeled energetics and flow pathways, and then estimating the quantities of sediment associated with these identified sources that may be contributing to the shoaling of the CSC. The results of these efforts were used to update the original sediment budget with estimates of the contributions from two additional sources: the erosion of interior wetlands and coastally derived sediments.
Speeding up development may produce technical debt, i.e., not-quite-right code for which the effort to make it right increases with time as a sort of interest. Developers may be aware of the debt as they admit it in their code comments. Literature reports that such a self-admitted technical debt survives for a long time in a program, but it is not yet clear its impact on the quality of the code in the long term. We argue that self-admitted technical debt contains a number of different weaknesses that may affect the security of a program. Therefore, the longer a debt is not paid back the higher is the risk that the weaknesses can be exploited. To discuss our claim and rise the developers' awareness of the vulnerability of the self-admitted technical debt that is not paid back, we explore the self-admitted technical debt in the Chromium C-code to detect any known weaknesses. In this preliminary study, we first mine the Common Weakness Enumeration repository to define heuristics for the automatic detection and fix of weak code. Then, we parse the C-code to find self-admitted technical debt and the code block it refers to. Finally, we use the heuristics to find weak code snippets associated to self-admitted technical debt and recommend their potential mitigation to developers. Such knowledge can be used to prioritize self-admitted technical debt for repair. A prototype has been developed and applied to the Chromium code. Initial findings report that 55\% of self-admitted technical debt code contains weak code of 14 different types.
La laguna de Ayarza, también nombrada “Lago Azul” por el color de sus aguas, se encuentra localizada al Norte del departamento de Santa Rosa (entre los municipios de Casillas y San Rafael Las Flores), a una altitud de 1,409 metros sobre el nivel del mar, tiene una extensión aproximada de 14 Km2. Los factores que intervienen en la determinación del estado trófico de un sistema léntico son: transparencia, contenido de fósforo total, nitrógeno total y clorofila. En el desarrollo de esta investigación se realizó la determinación del estado trófico con base, únicamente, en la transparencia y el nitrógeno total. Los valores obtenidos para ambos parámetros fueron comparados con la clasificación del grado de eutrofia de la OCDE (Organización de Cooperación Económica y Desarrollo, según sus siglas en Inglés) y de criterios de grados de eutrofización de Nürnberg y Suecia. De acuerdo con la transparencia promedio de la laguna de Ayarza (5.19 metros) y según la tabla del grado de eutrofia de OCDE se tiene que la laguna está dentro de los límites del estado mesotrófico. Comparando el valor promedio de nitrógeno total (0.60 miligramos/litro) con los criterios de Nürnberg y Suecia, se concluye que la laguna se encuentra ubicada dentro de los límites del estado mesotrófico.
En la cuenca del Lago de Atitlán en Guatemala, en específico en el departamento de Sololá, municipio de San Pedro la Laguna se construyó en el año 2016 un relleno sanitario para la disposición final de los desechos sólidos inorgánicos del municipio, el cual genera lixiviados cuyas características se desconocen, lo que ha impedido tomar medidas de control e implementar un tratamiento adecuado de los mismos. La presente investigación tuvo como finalidad evaluar el comportamiento de los lixiviados producidos por los desechos inorgánicos que se disponen en este relleno sanitario. Para ello se realizaron análisis durante la época seca y lluviosa de trece parámetros físicos y químicos, así como del volumen de lixiviados que se producen. Durante el estudio se evaluó la relación que existe entre las características fisicoquímicas del lixiviado y la precipitación que ingresa al relleno sanitario, quedando evidenciado que algunos parámetros como el cromo se incrementa en invierno pasando de un valor máximo en verano de 1.94 mg/l., a un máximo de 4.56 mg/l., en invierno, este comportamiento se repite en ocho de los parámetros evaluados en el estudio (demanda química de oxígeno, nitrógeno de amonio, fósforo total, ortofosfatos, alcalinidad, potasio, sodio y cromo). Con los resultados obtenidos se pudo determinar que el relleno sanitario genera un lixiviado considerado como joven. Este estudio podrá ser utilizado como referente para el tratamiento de lixiviados de rellenos sanitarios que produzcan lixiviados jóvenes y que reciban únicamente desechos inorgánicos dentro de la Cuenca del Lago de Atitlán.
Se realizó el diseño hidráulico de un modelo experimental de filtro percolador utilizando estopa de coco como medio filtrante. Se obtuvieron las siguientes características fisicoquímicas de la estopa de coco: absorción 164,42%, densidad 0,22 g/cm3, área superficial específica 50 m2/m3, humedad 11,87%, materia seca total 88,13%, extracto etéreo 0,33%, fibra cruda 45,83%, proteína cruda 2,15%, ceniza 5,63%, extracto libre de nitrógeno 46,06% y potencial de hidrógeno 5,01 unidades. Se utilizaron las ecuaciones de Eckenfelder y Bruce & Merkens para el cálculo de los parámetros de diseño los cuales fueron: caudal 1,21 m3/d, tiempo de retención 45 s, velocidad de filtración 4,59 m3/m2d, carga hidráulica vertical 2,29 m3/m3d, carga hidráulica superficial 0,046 m3/m2d, carga contaminante 0,2178 kg DBO5/d, carga orgánica vertical 0,4122 kg DBO5/m2d y carga orgánica superficial 0,0082 kg DBO5/m3d. La evaluación del modelo experimental respecto a Nitrógeno y Fósforo total fue: 41 mg/l en la entrada y 27 mg/l en la salida, con 33% de eficiencia en Nitrógeno total, 11,0 mg/l en la entrada y 13,1 mg/l en la salida, con una eficiencia negativa de 24% en Fósforo total (-24%).