bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical investigation on fluid-solid interaction of large-scale centrifugal pumps for pump station
Authors: Liu Shuai , Gao Yuhan , Zhi Yongming , Tan Lei
Published: June 2024

Large-scale centrifugal pumps are significant components in pump stations for water supply projects. In order to figure out the flow and vibration characteristics of large-scale centrifugal pumps, numerical investigation is carried out on the fluid-solid interaction of large-scale centrifugal pumps with stay vanes and adjustable guide vanes. SST k-ω turbulence model is employed to solve turbulent flow inside centrifugal pumps, and the simulated flow fields are imposed on solid impellers by one-way coupling method. The results show that the maximum deformation, maximum stress and maximum strain appear at the impeller outlet with the maximum radius under both schemes of stay vanes and adjustable guide vanes. In addition, compared with the scheme of stay vanes, the non-uniform distribution along circumferential distribution can be suppressed with the equipment of adjustable guide vanes, while the absolute value under adjustable guide vanes is larger than that under stay vanes.
PIV experimental study on water-sediment two-phase flow in NACA0012 cascade
Authors: Zhu Lei , Liu Zhen , Zhang Jianguang , Zhang Haiping , Rao Lei , Lu Li
Published: June 2024

Sediment wear is one of the important reasons for the damage of hydraulic machinery components, and the motion characteristics of sediment are the key factors to determine the degree of wear damage. In order to reveal the mechanism of sediment wear of turbine guide vane, motion characteristics of sediment near the wall of NACA0012 cascade were studied by PIV test method. In this research, fluorescent and sediment particles were used as tracer particles respectively, and the particle images of solid and liquid phases were recorded by double-camera synchronous imaging method. Finally, the synchronous velocity field of solid and liquid phases was determined by correlation analysis of particle images. The experimental results show that the PIV test method can accurately determine the motion characteristics of the solid phase. There is velocity slip between the solid phase and the liquid phase, and the velocity deviation is related to the factors of particle characteristics and Reynolds number.
Finite element numerical analysis of structural vibration of a certain pump station
Authors: Lu Shaopeng , Qiu Haiyun , Lei Xu , Wei Jiang , Fan Honggang
Published: June 2024

In the process of pump station operation, the vibration of factory structure caused by hydraulic or mechanical factors will seriously threaten the ordinary operation of pump station; reduce the efficiency of units; shorten the service lifespan of equipment, and even lead to failure of units. In this paper, ANSYS software and modal analysis method are applied to simulate the vibration effect on pump station under natural vibration, unit vibration excitation and hydraulic excitation. The intrinsic vibration features of pump station structure under diverse boundary conditions, different working conditions and distinct external excitation sources are studied. According to the results of modal and harmonic response analysis, it can be concluded that: 1. A cross relationship has been found existing between pump station structure and unit excitation of speed frequency. 2. In addition to the upper part of the pump station fragile structure, the vibration of the pier is more noteworthy. 3. The vibration amplitude of the whole pump station along vertical direction is larger than that in other directions while the deformation following the unit axis and flow direction presents a strong tendency. 4. In general, the influence of hydraulic load on the structural force of pump station is relatively small.
Stress measurement of runner blade for a Francis prototype turbine
Authors: Cao Dengfeng , Dodge Martin , Zhou Ye , Liu Juan
Published: June 2024

Fatigue crack on the runner blade is one of the severe threats to the operation safety of prototype turbine. Several factor, such as limited operation range, may lead to fatigue cracking commonly observed on Francis turbine. Several cases show that fatigue crack may reduce the working life of runner. The high stress during operation is one of main reasons to produce cracks. Hydraulic design, manufacture quality, deviation of operation condition and resonance may cause high stress on the runner blade. Because static and dynamic stress cannot be predicted with absolute certainty for all operating conditions, the most effective way to obtain the actual stress level of the blade is site measurement. In this paper, stress measurement is carried out on a Francis prototype turbine. Measurement results show that high static stress appears at a load range near full load, and high dynamic stress appears at lower loads. Finally, some practicable suggestions are proposed to reduce the stress of runner blade.
Optimal Design of Data Acquisition System for Fault Diagnosis of Hydraulic Machinery
Authors: Qiu H , Jin B , Zhao W , Wang Z
Published: June 2024

Fault diagnosis of hydraulic machinery has high requirements on the synchronization of monitoring data and the anti-interference of monitoring equipment. The performance and data quality of the existing operation monitoring equipment of the unit cannot meet the requirements. At the same time, due to the variety of sensors and the different wiring methods of different types of sensors, the preparation work such as wiring of data acquisition equipment in the test is complicated. This paper analyzes the application requirements of fault diagnosis data and the problems existing in the conventional data collection process. A data collection solution specified for diagnosis of hydraulic machinery, which better solves the problem of data synchronization, is designed. The new designed system has high sampling accuracy and anti-interference characteristics, as well as the advantages of strong capability and simple equipment deployment. The proposed system has been applied in multiple power stations, pumping stations and pump test platforms. The relevant functions have been effectively verified.
A unit commitment method of pumped storage in renewable energy system via a twofold particle swarm optimization algorithm
Authors: Ji L T , Jing X Y , Wang P , Zhang T , Xiao W D , Qin J , Wang R , Yang W J
Published: June 2024

The problem of unit commitment of pumped storage power stations (UCPS) is rarely discussed in existing works of multi-energy hybrid systems scheduling. It goes against accurately evaluating the operation performance and reliability of the pumped storage unit (PSU). This study proposes a co-optimization scheduling method for a Wind-Photovoltaic-Pumped storage system based on a twofold particle swarm optimization (TPSO). At the system layer, a standard PSO algorithm is used to optimize the output of the pumped storage plant (PSP). At the PSP layer, an improved discrete PSO based on three discrete variables is used to solve the UCPS problem. It uses the constraint patching and the micro-increment rate method, respectively, with detailed consideration of the constraints on PSP and the characteristics of the PSU. Finally, the results of a case study show that refined UCPS can reduce the regulation intensity indicators such as operating duration by more than 25%, with better consistency with the characteristics of units. This work could provide a guideline for improving the operation benefits and reliability of the PSP.
Exploration and application of welding technology for misalignment of pressure pipe orifices in a pumped storage power station
Authors: Mi Haitang , Feng Peilei , Chen Xiaoya , Zhu Anping , Guo Jianqiang , Liu Xiangxiang , Wang Shaohua , Wang Xi
Published: June 2024

Pumped storage power stations are currently the most economical and clean large-scale energy storage method. Pumped storage power stations have flexible start and stop, rapid response, and have six major functions, including peak shaving, valley filling, frequency regulation, phase modulation, emergency backup, and black start. With the transformation of the energy system towards clean, low-carbon, safe and efficient, the operational characteristics of the power system will undergo significant changes, requiring sufficient flexible regulation of power sources and energy storage facilities. It is more urgent to accelerate the development and construction of pumped storage energy. Due to the characteristics of pumped storage installation, high-strength pressure steel pipes are required on the upstream side of the power station units as the water diversion pipeline. This article takes a pumped storage power station as an example to analyze and handle the problem of pipe misalignment encountered during the welding process of pressure steel pipes in the power station. Satisfactory results have been achieved, ensuring the welding quality and providing reference for other engineering projects.
Analysis of Primary Frequency Modulation Performance Test for a Hydropower Station
Authors: Feng Peilei , Chen Xiaoya , Zhu Anping , Guo Jianqiang , Liu Xiangxiang , Wang Shaohua , Huang Shaozheng , Wu Jie , Xu Tianqi , Liu Zhijian
Published: June 2024

To ensure the safe operation of the power grid and generator units, fully utilize the primary frequency regulation capability of the generator units. Enable the grid connected operation team to adapt to changes in grid load and frequency at any time, and improve the control level of power quality and grid frequency. To verify the primary frequency regulation performance of the water turbine generator unit through a frequency regulation test. Test and determine the operating parameters of primary frequency regulation to meet the requirements of primary frequency regulation in the power grid, while ensuring the safe and stable operation of the unit. Provide reference basis for later unit operation through experiments.
Sensitivity analysis of influencing factors in large oscillation hydraulic transient process of pumped storage power station
Authors: Liu Tao , Hu Tengyao , Yuan Yanliang , Tang Lei , Wang Hongqing
Published: June 2024

The calculation of large oscillation transition process is of great significance for pumped storage power station, which is beneficial for ensuring the safe of the power station and extending the lifespan of the unit. Due to the presence of inertia in water and rotating components of the unit, as well as energy imbalance in the system, hydraulic transients will cause drastic changes in water pressure in the waterway system and unit speed, resulting in a sharp increase or decrease in pressure and a sharp change in unit speed, endangering the operational safety of the power plant and affecting the lifespan of the unit. It is necessary to optimize the layout of water conveyance system, basic parameters of units, and the closing law of guide vanes through calculation and analysis of large oscillation transition processes. Relying on a pumped storage power station in Guizhou, this paper analysis the sensitivity of the factors affecting the calculation results of the large oscillation transition process, such as runner characteristics, guide vane closing law, moment of inertia GD2, surge chamber diameter and restricted orifice size, to provide reference for similar projects.
Molecular dynamics simulation of C4F7N/CO2 mixed insulating gas
Authors: Zu Hongpeng , Lin Xin , Chen Kai
Published: June 2024

The substitution of SF6 in gas-insulated electrical equipment has become a hot issue in the electrical field, and the research on the green medium C4F7N and its gas mixture has attracted much attention. In this paper, the molecular dynamics simulation method was used to analyze the C4F7N and CO2 mixed insulating gas system in situ, and quantitatively simulate the concentration distribution, root mean square displacement, intermolecular interactions, and thermodynamic parameters of the insulating gases under the macroscopic conditions of different mixing ratios, pressures, and so on. The results show that by increasing the proportion of C4F7N at 298 K and 0.6 MPa, the mutual attraction between C4F7N and CO2 molecules is enhanced, which leads to the decrease of the diffusion rate of the two gases, and the gas distribution is uniform without obvious delamination phenomenon, which reflects the good compatibility. At the same time, the increase of the mixing ratio of C4F7N increased the adiabatic and isothermal compression coefficient of the gas mixture at 0.6~0.8 MPa accordingly, and the gas mixture did not show liquefaction phenomenon. This study provides a certain basis for designing the mixedinsulating gas ratios to meet engineering needs.
Verification and evaluation methods for pipeline leak detection algorithms
Authors: Chang Lingzhi , Fan Shidong
Published: June 2024

As an important equipment in energy transportation and utilization, state detection is a key link to ensure the safety and environmental protection of the equipment. At present, there are many types of pipeline leakage detection algorithms, but there is less verification and evaluation of the actual performance and characteristics of the algorithm. Therefore, based on the evaluation index system, the entropy weight method (EWM), and the TOPSIS, we build a pipeline leakage inspection evaluation model of the measurement algorithm. In addition, the actual liquid pipeline transportation experiment platform is established. The negative pressure wave method is selected and combined with the CNN-LSTM algorithms to perform experiments. The results show that the algorithm used in this paper is better than the traditional negative pressure wave algorithm (NPW). The performance and calculation results can provide a reference for scientific research, engineering, teaching, etc.
Numerical investigation on the energy extraction characteristics of parallel multi foils arranged in columns
Authors: Wang Yulu , Liu Tianyuan , Guo Kailun
Published: June 2024

The oscillating foil is a focus device in the clean energy utilization field. The presence of an oscillating foil structure within the flow field significantly impacts the energy extraction capabilities of the system. In this paper, three types of parallel multi-foil structures arranged in columns are proposed. The energy extraction characteristics of diverse multi-foil structures under various oscillation conditions are analyzed numerically. The flow field structure and the impact of parallel multi foils on the aerodynamic characteristics are investigated. Results demonstrate that the multi-foil structure with a phase difference of 180° achieves the highest level of energy extraction performance, and the maximal mean power coefficient achieves 0.894, which is 11.03% higher than that of the structure with a smaller phase difference. The size of the trailing edge vortex under the structure with a phase difference of 180° is significantly larger, leading to an obvious fluctuation in the aerodynamic lift.
Design of a mining carbon monoxide sensor and analysis of multi-gas cross-interference performance
Authors: Zhao Qingchuan , Liang Guangqing
Published: June 2024

A new type of carbon monoxide sensor is designed to address the issue of cross interference of nitrogen oxide gas in the exhaust emissions of underground diesel engine rubber-tired vehicles with electrochemical carbon monoxide sensors, which leads to frequent false alarm accidents. The hardware circuit design of the DC-DC voltage reduction power supply circuit, display circuit, component signal processing circuit, etc. is detailed, At the same time, the sensitive components used in the sensor adopt a special gas filtration membrane design. Six types of gases, including hydrogen sulfide, nitric oxide, nitrogen dioxide, hydrogen, ethylene, and acetylene, were sequentially introduced in the laboratory for experimental analysis of multi-gas cross-interference performance. The experimental results have shown that the new carbon monoxide sensor can filter out nitrogen oxide gas, thereby solving the impact of underground rubber tire vehicle exhaust on the accuracy of carbon monoxide gas detection. It has broad prospects for promotion and application in coal mines underground.
Investigation of resistance performance of anti-icing wave-plate separators for marine gas turbines intake system
Authors: Deng Zhiwei , Wang Zhongyi , Chen Xiaohu , Ma Wenqi
Published: June 2024

Due to their high power and efficiency, gas turbines are commonly used propulsion systems in hovercraft propulsion systems. In polar and cold marine environments, when a hovercraft rises, a significant number of droplets are generated on the water surface and are drawn into the gas turbine’s air intake with the cold air. This paper takes the structure of the original wave-plate separator as a reference and designs two structures: the rhombic anti-icing wave-plate separator (RAWS) and the streamlined anti-icing wave-plate separator (SAWS). Experimental and numerical simulation methods are employed to calculate the air intake resistance of the two structures at speeds ranging from 1 to 10 m/s. The results show that the K-ε standard enhanced wall function turbulent model is the closest to experimental measurements, with all calculated results having an error below 5%, demonstrating reliability. Compared to RAWS, the calculated total pressure loss for the SAWS structure decreases by 200 Pa under a designed air intake velocity of 7 m/s, representing a relative reduction of 40.8%. This provides a valuable reference for the design and resistance optimization of ship air intake anti-icing devices.
Study on evaporative condensation and heat and mass transfer characteristics of the second refrigerant in calorimeter
Authors: Zhou Kun , Zheng Mingyu , Xie Baogang , Yu Xiaolin , Xie Hongxi , Fu Wei , Shen Pengfei
Published: June 2024

A simulation study was conducted to explore the evaporative condensation and heat/mass transfer characteristics of the second refrigerant within the calorimeter. The objective was to establish both physical and mathematical models for the second refrigerant and to perform numerical simulations of the pressure and temperature fields within the calorimeter. The second refrigerant in the calorimeter was modeled physically and mathematically, and the pressure and temperature fields within the calorimeter were studied through numerical simulation. The findings indicate that with the input of electric heating power in the calorimeter, the pressure gradually rises alongside the temperature of the second refrigerant, leading to evaporation. Owing to the low surface temperature of the evaporation coil, the evaporated refrigerant vapor condenses on its surface, resulting in a decrease in temperature around the coil. The uneven distribution of temperature contributes to varying heat transfer rates across different areas of the calorimeter shell.x
Computational boundary improvement and performance optimization of the flue gas waste heat cascade utilization system of the ultra-supercritical 1000 MW generator set
Authors: Wang Xinyuan , Wang Dongqing , Wang Zeming , Shi Yuetao
Published: June 2024

There is no uniform performance test rule and standard calculation method for efficiency improvement of a system that utilizes waste heat from flue gas and it is mainly carried out through turbine parameters, without considering boiler system performance. Given the above problem, in this paper, the steam turbine, boiler and waste heat from the flue gas step-up utilization system are calculated by establishing a thermal model of ultra-supercritical secondary reheating 1000 MW unit. At the same time, unit design data and field performance test results are used for verification. Analysis comparing simulation outcomes with experimental data revealed that the discrepancies in the heat consumption rate per unit, the efficiency of the boiler, and the rate of coal consumption for power generation peaked at a marginal variance of 0.2%. The optimum operating parameters of the system for low-grade flue gas recovery in a cascading manner are obtained through variable operating condition calculations. The optimum value of high-pressure bypass feed-water flow rate is 52 kg/s at 970 MW operating condition. At the same time, the difference between high-pressure bypass effluent and high plus effluent temperatures should be controlled to be close to 0°C, and the optimal value of low-pressure bypass condensate flow rate is 53 kg/s. As the flow of flue gas in the bypass increases, the efficiency of heat exchange in the bypass economizer also increases, resulting in greater absorption of heat in the utilization apparatus for flue gas waste heat, leading to a more effective energy-saving outcome. However, it is necessary to regulate the temperature of both the primary and secondary air to levels that exceed the minimum requirements for the safe functioning of the coal mill.
Single pulse lightning and multiple lightning intrusion overvoltage in 500 kV GIS substation
Authors: Zhang Zongyang , Xu Weinian , Li Wenbing , Lu Chen , Chen Zehua , Zhang Sen , Duan Guanghui , Lu Hongbo
Published: June 2024

Lightning intrusion wave is a key factor threatening the safe operation of substations. This paper uses electromagnetic transient simulation software to calculate and analyze the overvoltage characteristics and influencing factors of lightning intrusion waves in GIS substations. It studies the effects of lightning current waveform, corona effect, and multiple lightning strikes on the lightning overvoltage. The results show that with the same amplitude of lightning current, the longer the duration and lower the steepness are, the lower the peak and steepness of lightning overvoltage invading the power station will be. As the distance between the lightning strike point and the substation increases, the attenuation effect of corona on lightning overvoltage shows a “not obvious-significant-saturation” pattern. When multiple lightning strikes occur, the peak and steepness of overvoltage caused by the first lightning strike are the highest, and the temperature rise of the lightning arrester varies linearly with the number of lightning strikes.
Research on wind farm power forecasting based on IGWO-CNN
Authors: Yin Yi , Wang Jiahan
Published: June 2024

An enhanced convolutional neural network (CNN) has been proposed to address the issue of low accuracy in wind farm power prediction using traditional methods, which leverages an improved version of the Gray Wolf Optimizer (IGWO). The standard Gray Wolf Optimizer (GWO) exhibits a linear change in the search range, which can limit its dynamic convergence capabilities. By incorporating nonlinear convergence factors and dynamic convergence strategies, the improved algorithm modulates the global search pace, effectively preventing it from getting stuck in local optima. The refined IGWO is subsequently applied to fine-tune the optimal CNN architecture, mitigating the uncertainty typically associated with the structural configuration of CNNs. When predicting the actual power measurements from a wind plant in Inner Mongolia, the results indicate that the IGWO-based CNN method outperforms both the conventional GWO-CNN approach and the standalone CNN regarding prediction accuracy.
High-precision substation electric energy metering device based on an adaptive algorithm
Authors: Wang Zhendong , Han Xueyu , Wang Yonggui
Published: June 2024

With the rapid development of science and technology, the structure of new power systems continues to advance, and the requirements for the digitalization and intelligence of power network operation equipment continue to improve. The use of electricity is increasing year by year, and the importance of using a variety of technologies to improve the accuracy of energy metering devices is becoming increasingly prominent. In this paper, a design scheme of a high-precision energy metering device based on an adaptive algorithm is proposed based on the in-depth study of many kinds of current energy metering terminals, in combination with the current detection technology and embedded technology. By improving the accuracy of the electric meter, the accurate measurement of electric energy can be achieved, and the operation ability of the power grid can be improved.
Coordinated operation of PV/EV/Temperature controlled loads in distribution network
Authors: Wang Chenyu , Hu Junjie
Published: June 2024

In order to solve the problems of voltage exceeding limits, local use, and reverse power flow due to the high proportion of distributed photovoltaic grid connections, a distributed photovoltaic uptake method considering demand-side resources and energy storage is proposed. Firstly, based on the equivalent thermal parameter (ETP) method, a load scheduling model for temperature-controlled loads is established. Secondly, with the objective function of minimizing the comprehensive operating cost of the distribution system, combined with the regulating effect of energy storage, stability and safety constraints for the distribution network, as well as the adjustable characteristics of thermal storage electric heating, air conditioning load, and electric vehicles, a demand side optimization model for the distribution network is established, which takes into account voltage safety and distributed photovoltaic uptake. Finally, based on historical data in Fengning County, Chengde City, and a certain park in Tangshan City, simulation analysis was conducted to obtain scheduling schemes and various scheduling indicators for the joint participation of demand-side resources and energy storage in the distributed photovoltaic local use of the distribution network under different permeability. The effectiveness and rationality of the proposed distributed photovoltaic consumption model were verified.
Design of unattended gas pumping station system based on multi-source data fusion
Authors: Wan Yong
Published: June 2024

Aiming at the problems that some data has been built and distributed in different subsystems during the transformation of the unattended system of an underground gas pumping pump station in Shanxi Tiandi Wangpo Coal industry, such as low data sharing and comprehensive utilization rate due to data isolation, and weak linkage execution ability, a method combining site-level data fusion and platform-level data fusion is proposed. The advantages and disadvantages of the fusion method are analyzed, and the PLC program and WinCC program are written for the corresponding fusion method. The practical application of the underground gas pumping pump station shows that the system has strong fusion ability, which can meet the integration of extraction parameters, environmental parameters, electric parameters, pipeline parameters, working conditions parameters, and other data required by the unattended system, improve the data utilization rate of the unattended system, and realize the complex control functions of the gas pumping system such as one-key start-stop and one-key rotation vacuum pump. The use of data-driven execution instead of manual operation effectively reduces the duty personnel of the underground gas pumping station, provides a guarantee for the less manned or unmanned operation of the gas pumping pump station, reduces the unplanned downtime of the pumping system, improves the efficiency of gas pumping, and ensures the safety of coal mine production.
Simulation study on the performance of heat pump air conditioning system for pure electric vehicles
Authors: Niu Junjia , Wang Yichun , Guo Fen
Published: June 2024

This study constructed an experimental bench for a R134a heat pump air conditioning system in a commercial electric vehicle. Based on the results from the experimental bench, the simulation model of the heat pump air conditioning system developed by AMESim was calibrated, and its reliability was verified. As the compressor and electronic expansion valve (EXV) are essential control components of the heat pump air conditioning system, simulations were conducted to investigate the impact of EXV opening on performance parameters such as refrigerating capacity, subcooling, superheat compressor power consumption, and Coefficient of Performance (COP) at different compressor speeds. The findings indicate that EXV opening significantly affects system subcooling and COP, and higher COP can be obtained by controlling the subcooling of the system through the EXV.
Research on reactive voltage control strategy for substations connected to photovoltaic systems
Authors: Ma Zhenliang , Liu Junwei , Jiang Jingxuan
Published: June 2024

The reactive voltage control of conventional substations is mainly realized by adjusting the switching of capacitors or reactors and changing the transformer ratio, which can only be controlled discretely. The PV inverter can carry out continuous reactive power control, and the reactive voltage control strategy of the conventional substation does not consider the reactive power control of the PV. In this paper, the nine-zone diagram control strategy of the traditional substation is used as a reference, and the reactive voltage optimization control strategy of a substation with a photovoltaic power generation system is constructed considering the characteristics that photovoltaic inverter can continuously regulate reactive power. Taking the internal power grid of an enterprise as an example, the simulation analysis verifies the effectiveness of the control strategy, which can ensure that the voltage and power factor of the grid-connected access point are qualified. At the same time, the voltage fluctuation of the grid-connected point can be reduced, and the network consumption can be reduced.
Simulink modeling analysis based on oil-electric hybrid six-rotor UAV
Authors: Tu Chuan , Liu Jianhong , Yan Zhiwei
Published: June 2024

Given the variable load caused by fuel consumption when the oil-electric hybrid six-rotor UAV is in actual flight, which leads to the slow response of flight attitude, Simulink modeling and analysis are carried out. Firstly, the Newton-Euler model is established for the UAV body by analyzing the motion dynamics of the UAV body. Then, the test method is used to model the oil-electric hybrid system, mainly considering the fuel consumption of the engine. The test results show that the transmission efficiency of the engine and the generator is 85 %, the maximum power of the engine can output 2.8 kW, the maximum power transmitted to the generator can output 2.38 kW, and the maximum power transmitted to the motor is 2.2 kW, which can realize the maximum peak power requirement of the UAV.
Mechanical and microstructural characterization of AISI SAE 4130 steel welded joints made by robotic gas metal arc welding process: influence of electrode work angle in 'T' welded joints
Authors: Wordofa Tesfaye Negash , Perumalla Janaki Ramulu , Sharma Abhay
Published: June 2024

Microstructural variations within welded metals, specifically in terms of phases and their corresponding volume fractions, play a crucial role in influencing weld strength and other mechanical properties. Welded joints in a ‘T’ configuration pose a unique challenge due to the dynamic heat distribution caused by changes in the electrode work angle (EWA) between perpendicularly aligned plates. This study focuses on characterizing the microstructure and micro-hardness of ‘T’ welded joints in a 6 mm thick plate of AISI SAE 4130, welded using the robotic gas metal arc welding process. The examination covers three distinct zones: the base material (BM), the fusion zone (FZ), and the heat-affected zone (HAZ). The extent of the HAZ is meticulously measured on both the vertical and horizontal plates within the weld zones. The x-ray diffraction (XRD) analysis results indicated that the average crystallite size of the base metal and fusion zone is 25.75 nm and 24.51 nm respectively. As per the scanning electron microscope (SEM) image observations, the higher wire feed rate yields to brittle fracture surface. The torch angles notably influence the dimensions of the HAZ on the vertical and horizontal plates of a ‘T’-Joint. Welding at higher EWA and contact-tip-work-distance, results in a larger HAZ on the vertical plate. Conversely, employing a flattened EWA and an increased contact-tip-work-distance leads to a greater extent of the HAZ on the horizontal plate. Furthermore, the micro-hardness of the fusion zone and heat-affected zone demonstrates an increase at higher settings of wire feed rate and travel speed. This phenomenon is attributed to the elevated heat inputs, which contribute to the formation of a finer microstructure within the weldment.
Asian summer monsoon responses under RCP4.5 and RCP8.5 scenarios in CESM large ensemble simulations
Authors: Choudhury Devanil , Nath Debashis , Chen Wen
Published: June 2024

The response of the Asian Summer Monsoon (ASM) circulation to the Representative Concentration Pathway 4.5 and 8.5 (RCP4.5 and RCP8.5) forcing scenarios is examined using the CESM1 state-of-the-art global circulation model from 2021 to 2050. The projections show that monsoon precipitation will increase over East Asia, the North Pacific Ocean, the Indian Peninsula, and the Bay of Bengal under the RCP4.5 scenario. Conversely, the South Indian Ocean, West Asia, the Middle East, and the Central Pacific Ocean exhibit a decreasing trend in precipitation. Under the RCP8.5 scenario, precipitation is projected to increase over a wider swath of the Indian Ocean and the Middle East Asia. In the RCP4.5 scenario, the low-level wind circulation is likely to strengthen over the entire northern Indian Ocean, extending to the South China Sea, thereby increasing moisture transport from the Indian Ocean to peninsular India and the South China Sea. Conversely, in the RCP8.5 scenario, easterly winds strengthen over the South Indian Ocean, leading to an increase in moisture transport from the equatorial West Pacific Ocean to the Indian Ocean. A weak (strong) cyclonic circulation in response to the east-centered (west-centered) low sea level pressure trend over the North Pacific in RCP4.5 (RCP8.5) scenario is projected to help maintaining a strong (weak) ASM circulation from the India to east Asia. Internal climate variability is also calculated, revealing that the North Pacific Ocean near the Bering Sea is likely to play a dominating role and contribute significantly to the future ASM dynamics. In both scenarios, internal variability is found to substantially contribute to changes in monsoon circulation over the Indian Ocean.
A note on surfaces in ℂℙ² and ℂℙ²#ℂℙ²
Authors: Marengon Marco , Miller Allison , Ray Arunima , Stipsicz András
Published: June 2024

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Making room for maladaptation
Authors: Madgwick Philip G
Published: June 2024

The chapter introduces the proposed concept maladaptation, and the argument of the book about the possibility, reality, and importance of maladaptation to the design of organisms. Evolution by natural selection is presented as the scientific explanation of organism design. Hereditary diseases are discussed as a potential outlier to this explanation, clarifying the separation of evolutionary pressures from chance and necessity, which broadly resolves the explanation of their evolution. Some harmful traits are identified to pose a more persistent problem that the book seeks to explain. The meaning of adaptation is established, and it is asked whether these problematic traits represent maladaptations. Multiple definitions of maladaptation are discussed, concluding that its current usage conflates different evolutionary pressures, owing to it being a neglected concept. Setting aside nonadaptation, a stricter definition is offered that presents maladaptation as the result of natural selection, with symmetry to the concept of adaptation. The implications and potential controversies of this definition are unpacked. Finally, the argument of the book is summarised, along with the key conceptual influences that have shaped it.
Deep origins of maladaptation
Authors: Madgwick Philip G
Published: June 2024

The chapter explores the relationship between life and maladaptation, arguing that maladaptation has been inextricably associated with life from its earliest origins in chemical evolution. The origin of life is discussed to establish the origin of the open-ended kind of natural selection that distinguishes biological evolution from its chemical counterparts. Theories of the origin of life are synthesised as either replicator- or organism-first, also identifying hybrid theories that blend elements of each. Despite experimental and theoretical progress, it is argued that the key challenge for understanding the origin of life remains one of imagination. A thought experiment is used to illustrate how chemical evolution has a tendency towards maladaptation, which must be overcome before biological evolution can take off. A simple mechanism is identified that explains not only how biological evolution can get started, but also why it was a probable beginning. Consequently, it is suggested that maladaptation was present from before the beginnings of biological evolution by natural selection, associating it inextricably with all living things.
Power saw noise levels during steel stud cutting tasks on commercial construction sites: a tool characterization from a worker exposure standpoint
Authors: Schutt David , Lipsey Tiffany , Van Dyke Mike , Brazile William J
Published: June 2024

Construction framers who cut and install steel studs as part of their daily tasks are exposed to hazardous noise levels during their work shift in large part due to the power saws they use to cut steel studs. This investigation characterized the sound pressure levels of power saws used to cut steel studs on active construction sites. Further, the length of time it took to cut various studs on a construction site was investigated to understand worker exposure times to saw noise. In general, power saws used on the study sites to cut steel studs had a mean A-weighted equivalent continuous sound pressure level (LAeq) of 107.2 dB and a C-weighted peak sound pressure level (LCpeak) of 120.1 dB. Three of the saws—the chopsaw, the cut-off saw, and the grinder—had similar noise levels, whereas the cordless circular saw had higher noise levels. It took an average of 13.2 s to cut each stud, and workers in the study used power saws to cut steel studs for an average of 371.5 s per day. This average exposure time at the average recorded sound pressure levels (SPLs) suggests these saws can increase the risk of occupational noise-induced hearing loss, according to National Institute for Occupational Safety and Health (NIOSH) recommendations.
Augmentation-Mastopexy With 4-Layer Autologous Fat Grafting and Evaluation of Viability With MRI
Authors: Kandulu Hüseyin
Published: June 2024

Background

Autologous fat (AF) grafting is widely used in plastic surgery and is generally considered a safe and effective procedure. A combined approach utilizing vibration amplification of sound energy at resonance (VASER) to prepare AF grafts with a 4-layer fat grafting technique was explored in this study.

Objectives

To offer a customized solution that accommodates individual anatomical differences.

Methods

This retrospective, cross-sectional case series involved 40 breasts from 20 female patients who underwent primary augmentation-mastopexy. After removing excess breast tissue and exposing the pedicle, lateral pillars, and pectoral muscle, the 4-layer fat grafting was performed as follows: 150 mL of AF under the pectoral muscle directed toward the medial and central zones; 100 mL into the pectoral muscle toward these zones; 50 mL under the pectoral fascia, moving retrograde from cephalic to caudal portions at a 30° to 45° cannula angle. After closing the epithelial and subepithelial incisions, an additional 100 to 150 mL of AF was injected under the subcutaneous layer around the breast, depending on each patient's contour and breast shape. Patients were monitored for 2 years with MRI scans to assess breast volume, anatomy, and fat graft survival.

Results

The average follow-up was 26 ± 2.81 months. MRI evaluations indicated an efficient survival rate of the fat grafts. None of the patients experienced minor or major complications.

Conclusions

The 4-layer AF grafting technique appears to be a safe and effective procedure for customized breast sculpting in augmentation-mastopexy surgery, with a high rate of fat graft sustainability and survival.

Level of Evidence: 4
Erythematous annular atrophic patchy lesions in the bilateral axillae
Authors: Uzuncakmak Tugba K , Bayındır Emre , Onenerk Ayse M , Melikoglu Melike
Published: June 2024

Cutaneous manifestations in dermatomyositis (DM) often lead to a reduced quality of life. We report a patient with axillary DM, a previously unreported cutaneous involvement of DM, to show that we may encounter different sites of involvement.
Successful thromboaspiration of bilateral pulmonary thromboembolism in a Fontan circulation patient: a case report
Authors: Rifé-Pardo Èlia , Rello Pau , Sambola Antonia , Gordon Blanca
Published: June 2024

Background

Fontan surgery aims to palliate univentricular congenital heart diseases in which biventricular repair is not feasible. A large spectrum of early and late complications has been described in literature. However, pulmonary thromboembolism represents a rare complication in these patients, leading to a scarcity of evidence regarding diagnosis and treatment strategies.

Case summary

We present a case of a 27-year-old woman born with a complex cyanotic congenital heart disease, namely pulmonary and tricuspid stenosis with subaortic interventricular communication and atrial septal defect, who underwent palliation surgery with Blalock–Taussig shunt, bidirectional Glenn, and extracardiac Fontan. She developed acute respiratory failure and was admitted to the hospital, being diagnosed with bilateral thromboembolism. Since she was haemodynamically stable, initially, a conservative approach was chosen. However, due to no clinical improvement, she subsequently underwent bilateral thromboaspiration with restoration of pulmonary circulation.

Discussion

Due to the unique Fontan pathophysiology, the possible physiological and clinical implications of pulmonary thromboembolism in this condition are profound. Thus, care and imaging tests in specialized centres are important as the management of these patients is different from those with biventricular physiology.
Acquisitions of safety-net hospitals from 2016–2021: a case series
Authors: Wood Christian , Chen Xinwei , Schpero William , Chatterjee Paula
Published: June 2024

Safety-net hospitals have recently become targets of acquisition by health systems with the stated purpose of improving their financial solvency and preserving access to safety-net services. Whether acquisition achieves these goals is unknown. In this descriptive case series, we sought to determine the factors that contribute to safety-net hospital acquisition, and identify whether safety-net services are preserved after acquisition. We examined 22 acquisitions of safety-net hospitals from 2016 to 2021 and described characteristics of the acquired safety-net hospitals, their acquiring systems, and the operational fate of acquired hospitals. Relative to other hospitals in the same Hospital Referral Region in the year prior to acquisition, acquired safety-net hospitals tended to be smaller and have lower occupancy rates. Acquiring systems were geographically concentrated, with only 6 of 20 systems operating in more than 1 state. Safety-net hospitals frequently offered typical safety-net services prior to acquisition. However, after acquisition, 2 of the 22 acquired safety-net hospitals lost safety-net services, 3 hospitals ceased inpatient services, and 1 hospital closed entirely. These findings suggest that acquisition of safety-net hospitals may be associated with trade-offs related to the provision of safety-net services for the communities that stand to benefit from them most.
Temporal evolution of ascending aortic aneurysm wall stress predicts all-cause mortality
Authors: Zamirpour Siavash , Gulati Arushi , Xuan Yue , Leach Joseph R , Saloner David A , Guccione Julius M , Boskovski Marko T , Ge Liang , Tseng Elaine E
Published: June 2024

OBJECTIVES

Diameter-based risk stratification for elective repair of ascending aortic aneurysm fails to prevent type A dissection in many patients. Aneurysm wall stresses may contribute to risk prediction; however, rates of wall stress change over time are poorly understood. Our objective was to examine aneurysm wall stress changes over 3–5 years and subsequent all-cause mortality.

METHODS

Male veterans with <5.5 cm ascending aortic aneurysms and computed tomography at baseline and 3- to 5-year follow-up underwent three-dimensional aneurysm model construction. Peak circumferential and longitudinal wall stresses at systole were calculated using finite element analysis. Temporal trends were assessed by mixed-effects modelling. Changes in aortic wall stresses, diameter and length over time were evaluated as predictors of subsequent 3-year all-cause mortality by Cox proportional hazards modelling.

RESULTS

Sixty-two male veterans were included in the study. Yearly changes in geometric and biomechanical measures were 0.12 mm/year (95% confidence interval, 0.04–0.20) for aortic diameter, 0.41 mm/year (0.12–0.71) for aortic length, 1.19 kPa/year −5.94 to 8.33) for peak circumferential stress, and 0.48 kPa/year (−3.89 to 4.84) for peak longitudinal stress. Yearly change in peak circumferential stress was significantly associated with hazard of death—hazard ratio for peak circumferential stress growth per 10 kPa/year, 1.27 (95% CI, 1.02–1.60; P = 0.037); hazard ratio for peak circumferential stress growth ≥ 32 kPa/year, 8.47 (95% CI, 2.42–30; P < 0.001).

CONCLUSIONS

In this population of nonsurgical aneurysm patients, large temporal changes in peak circumferential stress, but not aortic diameter or length, was associated with all-cause mortality. Biomechanical stress and stress changes over time may be beneficial as additional risk factors for elective surgery in small aneurysms.