Force control in hydraulic actuators is notoriously difficult due to strong nonlinearities, uncertainties, and the high risks associated with unsafe exploration during learning. This paper investigates safe reinforcement learning (RL) for hy draulic force control with real-world training using contraction metric certificates. A data-driven model of a hydraulic actuator, identified from experimental data, is employed for simulation based pretraining of a Soft Actor-Critic (SAC) policy that adapts the PI gains of a feedback-linearization (FL) controller. To reduce instability during online training, we propose a quadratic-programming (QP) contraction filter that leverages a learned contraction metric to enforce approximate exponential convergence of trajectories, applying minimal corrections to the policy output. The approach is validated on a hydraulic test bench, where the RL controller is trained directly on hardware and benchmarked against a simulation-trained agent and a fixed-gain baseline. Experimental results show that real-hardware training improves force-tracking performance compared to both alternatives, while the contraction filter mitigates chattering and instabilities. These findings suggest that contraction-based certificates can enable safe RL in high force hydraulic systems, though robustness at extreme operating conditions remains a challenge.
In 2019, a fluoride overfeed in the drinking water system of Sandy City, Utah, USA, sickened residents, corroded pipes, and released lead and copper. Sandy operators changed practices immediately, state water regulators issued administrative orders in following years, and in 2025, due partly to the incident and partly to national mood, the Utah legislature banned water fluoridation altogether—the first such ban in the United States. This case study examines the incident's technical failures (in equipment settings, control logic, and hydraulics), procedural failures (in water sampling, record keeping, and public notification), and how changes in fluoridation practice and policy escalated from a single local event to the national stage.
ABSTRACT Dams are built for many purposes, one of the most important of which is to reduce the impact of floods. They release water downstream in a controlled manner through spillway structures. Spillways are critical structures that must be designed with low‐risk criteria to withstand floods that occur once every thousand years. This paper presents a three‐dimensional CFD simulation of the flow over a prototype spillway and validates the results with experimental data. The spillway belongs to the Çatalan Dam, which was constructed in 1985 for hydroelectric power generation. A 1:100 physical model of the Çatalan Dam spillway was built based on Froude similarity, and velocities in the discharge channel were measured at specific cross‐sections and points. The numerical model used the Volume of Fluid (VOF) method and the k‐ε Standard model. The velocity values from the numerical model were compared with experimental velocity values, showing good agreement. Additionally, pressure values were obtained from the numerical model, and cavitation index values were computed accordingly. The results indicated no cavitation risk in the prototype spillway, as the index values remained above 0.2 at all points in the cross‐sections.
River protective works. Regulation. Flood control, Disasters and engineering
Mehdi Heydari Shahna, Pauli Mustalahti, Jouni Mattila
In-wheel drive (IWD) systems enhance the responsiveness, traction, and maintenance efficiency of vehicles by enabling each wheel to operate independently. This paper proposes a novel robust torque-observed valve-based control (RTOVC) framework to address velocity tracking in hydraulic IWDs that actuate heavy-duty wheeled mobile robots (HWMRs), considering such challenges as wheel slippages, sensor limitations, rough terrains, and modeling uncertainties. To overcome the sensor-dependent control systems associated with the closed-loop torque/pressure in hydraulic IWD-actuated HWMRs, a robust observer network based on an adaptive barrier Lyapunov function (BLF) is proposed to estimate the required in-wheel motor torque to track the velocity references. Then, another adaptive BLF for valve control signals is employed to modulate the hydraulic fluid to generate the estimated torque for each IWD. The RTOVC strategy ensures user-defined safety within the logarithmic BLF framework by constraining the valve control signal, actual velocity, velocity tracking error, and torque of each hydraulic IWD in an HWMR to avoid exceeding specified limits. Despite its safety constraints, external disturbances, and modeling uncertainties, robustness and uniformly exponential stability of the RTOVC-applied hydraulic IWD mechanism are ensured in HWMRs. Experimental investigations using a 6,500-kg HWMR, actuated by four independent IWDs under intense disturbances and safety-defined constraints, validate the performance of the RTOVC.
The confluence of soft robotics and fluidic logic have sparked innovations in integrated robots with superior flexibility and potential machine intelligence. However, current fluidically driven soft robots suffer from either a large number of input controlling devices, or limited driving power. Here, we propose a hydraulic fluidic logic circuitry for liquid driven soft robots, leveraging 3D printing technologies. The fundamental building blocks of the system are hydraulic normally-on and normally-off logic gates, namely NOT and AND, along with a multi-connected channel structure functioning as OR. Using minimal-input design principles, the XOR gate can be simplified to only two valves, and used to construct a sensor-free error detector. The design principle can also be extended to full adders, as well as amplifiers, which can greatly improve the flow efficiency of the system. Additionally, taking advantage of the incompressible nature of liquid and optimized logic circuitry using the minimal-input design principle, we present a quadruped soft robot integrated with combinational fluidic logic, realizing bidirectional turtle-like locomotion, controlled by only two inputs. The robot is capable of walking under heavy load and performing controllable underwater locomotion. This hydraulic fluidic soft robotic system utilizes a small number of inputs to control multiple distinct outputs, and alters the internal state of the circuit solely based on external inputs, holding significant promises for the development of microfluidics, fluidic logic, and intricate internal systems of untethered soft robots with machine intelligence.
In this report, we present ChuXin, an entirely open-source language model with a size of 1.6 billion parameters. Unlike the majority of works that only open-sourced the model weights and architecture, we have made everything needed to train a model available, including the training data, the training process, and the evaluation code. Our goal is to empower and strengthen the open research community, fostering transparency and enabling a new wave of innovation in the field of language modeling. Furthermore, we extend the context length to 1M tokens through lightweight continual pretraining and demonstrate strong needle-in-a-haystack retrieval performance. The weights for both models are available at Hugging Face to download and use.
Nam Le Hai, Anh M. T. Bui, Phuong T. Nguyen
et al.
Technical debt (TD) describes the additional costs that emerge when developers have opted for a quick and easy solution to a problem, rather than a more effective and well-designed, but time-consuming approach. Self-Admitted Technical Debts (SATDs) are a specific type of technical debts that developers intentionally document and acknowledge, typically via textual comments. While these comments are a useful tool for identifying TD, most of the existing approaches focus on capturing tokens associated with various categories of TD, neglecting the rich information embedded within the source code. Recent research has focused on detecting SATDs by analyzing comments, and there has been little work dealing with TD contained in the source code. In this study, through the analysis of comments and their source code from 974 Java projects, we curated the first ever dataset of TD identified by code comments, coupled with its code. We found that including the classified code significantly improves the accuracy in predicting various types of technical debt. We believe that our dataset will catalyze future work in the domain, inspiring various research related to the recognition of technical debt; The proposed classifiers may serve as baselines for studies on the detection of TD.
Ammonia (NH3) is a highly reactive gas with impacts on environmental aspects such as air quality, visibility, climate change, acid deposition, and eutrophication. Major global sources of NH3 emissions are from agriculture, urban activities, and wildfires. NH3 serves as a vital precursor to secondary aerosol particle formation, eventually transforming into ammonium (NH4+) within the atmosphere.
This study is centered in Brandenburg, Germany, examining land cover classifications and NH3emissions using satellite-based Earth observation methods. These techniques encompass monitoring both spatial and temporal variations in ground surface sources and the total column of NH3 emissions. Additionally, NH3 emissions are detected in the atmosphere using the Meteorological Operation Satellite (MetOp-B) with the Infrared Atmospheric Sounding Interferometer (IASI). A detailed Land Cover Classification map at 10 m resolution is employed. Furthermore, the study utilizes MODIS Aqua/Terra data to collect information on active fires. The results of this research illustrate the comprehensive analysis of land cover classifications and NH3 emission patterns in Brandenburg. The annual mean NH3emissions from 2013 to 2022 reveal consistent values, with noticeable increases observed during specific years in northern Brandenburg. The annual distribution of fire spots, as recorded by MODIS Aqua/Terra, highlights potential correlations between fire incidents and ammonia emissions. Notably, boxplot time series data present an intriguing pattern where nighttime NH3 concentrations consistently surpass daytime levels. In the future, this study aims to employ a multiplatform approach integrating satellite and ground-based observations of aerosol optical depth (AOD) in the atmosphere, with a specific focus on the presence of NH3.
T. N. Postnikova, O. O. Rybak, A. S. Gubanov
et al.
Probable scenarios of future changes in the Elbrus glaciers and associated with them phenomena such as formation of glacial lakes and remaining ice masses buried under the debris cover are considered. The SSP scenarios (SSP1–1.9, SSP1–2.6, SSP2–4.5, SSP3–7.0, SSP5–8.5) were used for of future climate forcing. Glacier dynamics was simulated using the GloGEMflow model, which was improved by including a module of evolving debris cover. According to the prognostic calculations of the surface mass balance of the glaciers, the loss of ice mass on the Elbrus will accelerate until the end of the 2030s, reaching approximately –1.1±0.3 m w. e. yr. –1 . The volume of the glacier ice is expected to be reducing almost linearly until about 2040, after which the mass loss rate will slow down. Under the warmest climate change scenarios (SSP5–8.5, SSP3–7.0), almost all of the remaining ice masses in the North Caucasus will be concentrated on Elbrus by the end of the century. At the same time, by 2100 the glaciers of Elbrus themselves will retreat up to 4000 m above sea level and higher. In case of moderate warming (SSP1–1.9, SSP1–2.6) the position of glacier fronts maybe stabilized at an altitude of 3600–3700 m. The study concerns also the dynamics of the debris cover, predicting its doubling in area and average thickness of 0.22 m by 2040. Although the effect of the debris cover on the total volume of ice on Elbrus is estimated to be minimal, it can temporarily slow down melting of the frontal parts and areas of dead (remaining) ice. According to our estimates, the retreat of the Elbrus glaciers may result in formation of up to 17 new lakes, of which six may potentially be temporarily dammed by dead (remaining) ice zones (up to 60 m thick for Djikaugenkioz). It is expected that the largest lake may be formed on the Djikaugenkioz plateau, it will be dammed by moraine with ice buried under it in the period from 2035 to 2045 if no sufficiently efficient runoff channels will appear. The approximate time and place of formation of such ice masses near the sites of lake formation, depending on the climatic scenario, are shown in the paper, since it is important from the point of view of the risk of outburst floods in the 21st century. Under moderate warming (scenario SSP1–2.6), up to 8 lakes are likely to be formed at the site of retreating glaciers Ulluchiran, Djikaugenkioz, and Bolshoy Azau. All of them may appear in the first half of the century, regardless of the climatic scenario.
Łukasz Warguła, Piotr Kaczmarzyk, Bartosz Wieczorek
et al.
The air–fuel ratio is a crucial parameter in internal combustion engines that affects optimal engine performance, emissions, fuel efficiency, engine durability, power, and efficiency. Positive pressure ventilators (PPVs) create specific operating conditions for drive units, characterized by a reduced ambient pressure compared to standard atmospheric pressure, which is used to control carburetor-based fuel supply systems. The impact of these conditions was investigated for four commonly used PPVs (with internal combustion engines) in fire services across the European Union (EU), using a lambda (λ), carbon dioxide (CO<sub>2</sub>), carbon monoxide (CO), and hydrogen carbon (HC) analyser for exhaust gases. All four ventilators were found to operate with lean and very lean mixtures, with their lambda coefficients ranging from 1.6 to 2.2. The conducted tests of the CO<sub>2</sub>, CO, and HC concentrations in the exhaust gases of all four fans show dependencies consistent with theoretical analyses of the impact of the fuel–air mixture on emissions. It can be observed that as the amount of burned air decreases, the values of CO and HC decrease, while the concentration of CO<sub>2</sub> increases with the increase in engine load. Such an operation can accelerate engine wear, increase the emission of harmful exhaust gases, and reduce the effective performance of the device. This condition is attributed to an inadequate design process, where drive units are typically designed to operate within atmospheric pressure conditions, as is common for these engines. However, when operating with a PPV, the fan’s rotor induces significant air movement, leading to a reduction in ambient pressure on the intake side where the engine is located, thereby disrupting its proper operation.
In this paper, a controller design targeting the remotely operated hydraulic drive system is presented. A two-degrees-of-freedom PID position controller is used, which is designed so that to maximize the integral action under robust constraint. A linearized model of the system plant, affected by the parameters uncertainties such as variable communication time-delay and overall system gain, is formulated and serves for the control design and analysis. The performed control synthesis and evaluation are targeting the remote operation where the wireless communication channel cannot secure a deterministic real-time of the control loop. The provided analysis of uncertainties makes it possible to ensure system stability under proper conditions. The theoretically expected results are confirmed through laboratory experiments on the standard industrial hydraulic components.
The capability to simulate a hydraulic fracturing process is an essential tool that can be used to optimize treatment design and increase the efficiency of field operations. In most practical cases, hydraulic fractures propagate in a multi-layered rock formation. As a result, there is a need to incorporate the effect of such heterogeneities in fracturing models to achieve an accurate prediction. To capture the layered structure of rocks, a hydraulic fracture simulator typically requires a fine mesh, which leads to a drastic reduction in computational performance. An alternative is to use more sophisticated models that are capable of providing reasonably accurate predictions even on a relatively coarse mesh. In the case of fracture growth modeling, the pivotal component of the simulation is a fracture front tracking algorithm that accounts for the layered structure of the formation. Consequently, this paper aims to extend the established Implicit Level Set Algorithm (ILSA) to account for the effect of multiple stress layers within the tip asymptote. The enhanced front tracking algorithm involves the stress-corrected asymptote that incorporates the influence of stress layers within the near-tip region. To further increase the validity region of the stress-corrected asymptote, the stress relaxation factor is introduced, and its accuracy is examined. The numerical algorithm is validated against the reference semi-analytical solutions as well as experimental observations. In addition, we investigate the sensitivity of the fracture geometry to mesh size to demonstrate that the front tracking algorithm based on the stress-corrected asymptote retains its accuracy on a coarse mesh.
Felix Rocael Martínez Gómez, Walter Arnoldo Bardales Espinoza
La erosividad es uno de los seis factores de la Ecuación Universal de Pérdidas de Suelo (USLE). Para implementar las técnicas correctas de conservación de suelos es necesario conocer la variación espacial y temporal de la erosividad. El objetivo de este estudio fue generar modelos para estimar la erosividad anual en el pacífico de Guatemala a través de información pluviométrica de 28 estaciones del Instituto Privado de Investigación sobre Cambio Climático de Guatemala (ICC). Se desarrollaron dos modelos para cada estación utilizando como variable independiente los datos de precipitación diaria y mensual, y tres modelos regionales utilizando como variable independiente la precipitación diaria, mensual y anual de todas las estaciones. La erosividad de cada tormenta fue calculada según la metodología propuesta por Wischmeier & Smith (1978). Los registros de lluvia y erosividad de las estaciones se ajustaron a un modelo de tipo R=(αP)^β. La calidad de los resultados de las erosividades observadas y estimadas se evaluaron por medio de los estadísticos porcentaje de bias (PBIAS), coeficiente de Nash-Sutcliffe (NSE), la razón de la desviación estándar (RSR) y análisis de varianza. Los mejores resultados de la estimación de la erosividad anual se obtuvo cuando se utilizaron los modelos regionales con datos de precipitación mensual y anual. El mejor modelo para la estimación de erosividad podrá utilizarse para generar información en lugares donde solamente existen pluviómetros o bien para extender series de erosividad a escala mensual y anual en el pacífico de Guatemala.
Muhammad Shodiq Supriyanto, Muhammad Cahyono, Eka Oktariyanto Nugroho
et al.
Abstract
Human activities in coastal area will generally lead to a greater erosion rate due to the loss of natural protection or inappropriate structure. Dadap Beach, located at Juntinyuat District, Indramayu, West Java is one of the locations experiencing problems above. In 2003, a Fishing Port was built on Dadap Beach, with structure jutted 200 m from the shoreline to prevent sedimentation. However, currently there has been a massive sediment deposition in the port pool and behind the port. This study aims to determine the sedimentation pattern in Dadap Port, and the influence of the port structure on the coastal morphology, using a numerical model simulation. The results of this study indicate that the presence of the port structure has caused wave diffraction that forms a circulation flow behind the port structure and around the entrance area to the port pool, that lead to the formation of a tombolo behind the port and the sediment from the longshore currents and local scour enters the port pool area. Furthermore, the existence of Dadap port structure causes the obstruction of longshore currents so that the supply of sediment to the area around the port is reduced and the erosion rate is increasing.
Keywords : Erosion, coastal morphology, numerical model.
Abstrak
Aktivitas manusia di wilayah pesisir umumnya akan menyebabkan bertambahnya laju erosi, yang disebabkan oleh hilangnya perlindungan alami atau pembangunan struktur yang tidak sesuai. Pantai Dadap yang terletak di Kecamatan Juntinyuat, Indramayu, Jawa Barat merupakan salah satu lokasi yang mengalami permasalahan di atas. Pada tahun 2003, dibangun Pelabuhan Perikanan di Pantai Dadap, dengan struktur menjorok 200 m dari garis pantai untuk mencegah sedimentasi. Namun, pada saat ini telah terjadi pengendapan sedimen yang masif di kolam pelabuhan dan di belakang pelabuhan. Studi ini bertujuan untuk mengetahui pola sedimentasi di Pelabuhan Dadap, dan pengaruh struktur pelabuhan terhadap morfologi pantai, dengan menggunakan simulasi model numerik. Hasil studi ini menunjukkan bahwa keberadaan struktur pelabuhan telah menyebabkan difraksi gelombang yang membentuk aliran sirkulasi di belakang struktur pelabuhan dan di sekitar area pintu masuk ke kolam pelabuhan, yang menyebabkan terbentuknya tombolo di belakang pelabuhan dan sedimen dari arus sejajar pantai dan gerusan lokal memasuki area kolam pelabuhan. Selain itu, keberadaan struktur pelabuhan Dadap menyebabkan terhambatnya arus sejajar pantai sehingga suplai sedimen ke daerah sekitar pelabuhan berkurang dan laju erosi semakin meningkat..
Kata-kata Kunci : Erosi, morfologi pantai, model numerik.
In order to realize the power supply of small nuclear reactors in remote areas, the sub-channel analysis program BRESA of supercritical carbon dioxide (S-CO2) fuel assembly based on Modelica language was developed in this paper. According to the fuel assembly model of 37 rods, the axial and radial physical and thermal parameters of S-CO2 fuel assembly were calculated, and the flow mixing effect between channels was introduced to obtain the distribution law of thermal hydraulics parameters in the axial and radial directions, The enthalpy rise and temperature rise changes of various typical channels were studied. The results show that the enthalpy rise and temperature rise changes of the channel in the middle of the fuel assembly are high, while the enthalpy rise and temperature rise changes of the channel at the edge of the fuel assembly are low. Through comparison with relevant literature, it is proved that the thermal hydraulic parameters of this study meet the design requirements and the correctness of the program is verified. On the basis of steady-state calculations, the transient conditions of flow rate changes were analyzed, and the response characteristics of various parameters of fuel assemblies under transient conditions of linear increase, linear decrease, and sudden change in flow rate were analyzed. The response characteristics of reactor power response and control system were investigated and analyzed, and the spatial variation trends of enthalpy and pressure with time were obtained. The results indicate that under transient conditions, the reactor power will vary with flow fluctuations, which is related to the negative feedback effect of the control system and temperature. The pressure and enthalpy values also fluctuate and change when the flow rate changes, which is influenced by the dual effects of flow rate and power changes. Under transient conditions of sudden flow changes, enthalpy and pressure undergo sudden and significant fluctuations, with the maximum fluctuation of outlet enthalpy reaching 12%, posing a challenge to the safe operation of the reactor. The research results of this paper provide theoretical support and technical guidance for the design and research of supercritical carbon dioxide reactor systems.
This paper describes the Around View Monitoring (AVM) system for hydraulic excavators that prevents the safety accidents caused by blind spots and increases the operational efficiency. To verify the developed system, experiments were conducted with its prototype. The experimental results demonstrate its applicability in the field with the following values: 7m of a visual range, 15fps of image refresh rate, 300ms of working information data reception rate, and 300ms of surface condition data reception rate.
The appearance of infinity together with collapsing quantum state due to the observation or interaction, which are two challenging features of quantum field theory, become very serious problems in quantum gravity as well as in quantum geometry of space-time. These problems can be divided into two categories: technical and conceptual parts. In the technical aspect, the biggest problem comes from the definition of the point, which constructs classical geometry. By changing the point definition, the technical problem may be approximately bypassed, and a mathematical formulation of quantum geometry may be found. On the other hand, the conceptual problem comes from the quantum state collapse due to the observation since the entanglement between the observer and gravity cannot be eliminated in the presence of gravity. The conceptual part does not depend on the techniques which are employed. As much as possible, we try to discuss these problems by rediscovering the perception and understanding of a phenomenon for an observer in quantum theory.