Search Results (189)

Background: Orthostatic hypotension can occur during acute spinal cord injury (SCI) and subsequently persist. We investigated whether a gait rehabilitation robot combined with functional electrical stimulation (FES) stabilizes hemodynamics during orthostatic stress in SCI. Methods: Six intermediate-phase SCI patients (five males and one female; mean age: 49.5 years; four with quadriplegia and two with paraplegia) participated. The participants underwent robotic training (RT), with a gait rehabilitation robot combined with FES, and tilt table training (TT). Hemodynamics were monitored using a laser Doppler flowmeter for the earlobe blood flow (EBF) and non-invasive blood pressure measurements. The EBF over time and the resting and exercise blood pressures were compared between each session. Adverse events were also evaluated. Results: The EBF change decreased in TT but increased in RT at the 0.5-min slope (p = 0.03). Similarly, the pulse rate change increased in TT but decreased in RT at the 1-min slope (p = 0.03). Systolic and mean blood pressures were slightly higher in RT than in TT but not significantly (p = 0.35; 0.40). No adverse events occurred in RT, but two TT sessions were incomplete due to dizziness. Conclusions: RT with FES can reduce symptoms during orthostatic stress in intermediate-phase SCI. Future studies require a larger number of cases to generalize this study. Full article

Ultrasonic flowmeters are essential sensor devices widely used in remote metering systems, smart grids, and monitoring systems. In these environments, a low-power design is critical to maximize energy efficiency. Real-time data collection and remote consumption monitoring through remote metering significantly enhance network flexibility and efficiency. This paper proposes a low-complexity structure that ensures an accurate time-of-flight (ToF) estimation within an acceptable error range while reducing computational complexity. The proposed system utilizes Hilbert envelope detection and a differentiator-based parallel peak detector. It transmits and collects data through ultrasonic transmitter and receiver transducers and is designed for seamless integration as a node into wireless sensor networks (WSNs). The system can be involved in various IoT and industrial applications through high energy efficiency and real-time data transmission capabilities. The proposed structure was validated using the MATLAB software, with an LPG gas flowmeter as the medium. The results demonstrated a mean relative deviation of 5.07% across a flow velocity range of 0.1–1.7 m/s while reducing hardware complexity by 78.9% compared to the conventional FFT-based cross-correlation methods. This study presents a novel design integrating energy-efficient ultrasonic flowmeters into remote metering systems, smart grids, and industrial monitoring applications. Full article

The paper deals with the analysis of the fuel consumption of skidders during timber extraction from thinning of even-aged beech forest on mountain terrain. Fuel consumption research was conducted on the Ecotrac 140V cable skidder over 8 working days at the same worksite during real timber extraction work. The worksite was organized so that the empty skidder traveled uphill, and when loaded, it moved downhill. The skidder was equipped with measuring devices for collecting data from sensors, the motor, and data transfer. The key parameters measured include total fuel consumption (mL) and skidder GPS position, while slopes of skid trails and load volumes were measured directly on terrain. Fuel consumption (L, L/m³) was determined per work cycle and work cycle elements. The highest fuel consumption occurred while driving the unloaded skidder, accounting for 38% of the total. This is primarily because fuel usage during skidder movement is significantly affected by factors such as skidding distance, slope, and skid trail conditions, especially since the unloaded skidder was moving uphill. Guidelines for better and more efficient organization of work and reduction in fuel costs are presented, and the suitability of the skidder and harvesting system are considered based on the results of fuel consumption. Full article

The plate flowmeter offers a novel method for water flow measurement in small channels. Characterized by its simple construction, absence of siltation, and consistent relationship between the deflection angle and flow rate, this device possesses significant potential. Our study, employing rigorous experimental techniques, validated that the gate-hole outflow calculation model is effectively applicable to this plate flowmeter. Additionally, our research investigated the device’s impact on flow velocity distribution. Our findings reveal that the plate flowmeter can be effectively combined with the sluice gate outflow model. It has been verified that the maximum relative error is 14.57%, the minimum relative error is 0.35%, and most relative errors are below 10%. Both water level and flow rate contribute to the flat plate device’s relative head loss, with water level exerting a more significant effect. At various points along the channel, the plate flowmeter affects flow velocity distribution differently. Upstream, the device minimally impacts vertical flow velocity distribution, resulting in steady velocity changes. Conversely, downstream, the flat plate flow meter significantly alters flow velocity distribution, prompting redistribution that persists until 1.26 m downstream, where device influence ceases. These insights offer a solid theoretical foundation for enhancing the structural design of the plate flowmeter, thus improving its overall performance and efficacy. Full article

To address the research gap regarding the flow characteristics of cryogenic perforated plate flowmeters in vertical pipes and to enhance measurement reliability in challenging environments, this study investigates the flow characteristics of liquid hydrogen in a vertical pipe using a perforated plate flowmeter. Numerical simulations are performed based on an extended derivation of performance parameter formulas in the vertical direction. Various inlet Reynolds numbers, plate thicknesses, and equivalent diameter ratios are analyzed to assess their effects on key performance parameters, including the discharge coefficient, pressure loss coefficient, and stable region. The results indicate that the influence of flow direction on the performance parameters decreases with increasing Reynolds number. Downward flow is associated with smaller discharge coefficients, lower pressure loss coefficients, and reduced upper limits of Reynolds numbers in the stable region. Furthermore, the effects of gravity become more pronounced at larger thicknesses and greater equivalent diameter ratios. Full article

To address the challenge of precise flow rate measurement in microchannels, this research details the conceptualization and comprehensive evaluation of a thermal flowmeter which works on the principle of calorimetry for measuring small flow rates between 0.1 and 180 mL/h. The thermal flowmeter is composed of a silicone pipe, a heater, three platinum thermal sensors (T₁, T₂, T₃), and water as the working fluid. The flowmeter is strategically placed to monitor the complex thermodynamics between upstream and downstream flows. The analysis revealed a notable decay in the slope of the temperature differences beyond a flow rate of 40 mL/h, indicating the exceptional sensitivity of the device at lower flow rates and making it an ideal choice for medical applications. Parametric analysis was also carried out to place the sensors at optimized locations for better sensitivity. Full article

This work contributes to the improvement of novel medical technologies for the prevention and treatment of diseases. Electrical impedance tomography (EIT) has gained attention as a valuable tool for non-invasive monitoring providing real-time insights. The purpose of this work is to develop and validate a novel portable EIT system with a small form factor for respiratory monitoring. The device uses a 16-electrode architecture with adjacent stimulation and measurement patterns, an integrated circuit current source and a single high-speed ADC operating with multiplexers to stimulate and measure across all electrodes. Tests were conducted on 25 healthy subjects who performed a pulmonary function test with a flowmeter while using the EIT device. The results showed a good performance of the device, which was able to recognize all respirations correctly, and from the EIT signals and images, correlations of 96.7% were obtained for instantaneous respiratory rate and 96.1% for tidal volume prediction. These results validate the preliminary technical feasibility of the EIT system and demonstrates its potential as a reliable tool for non-invasive respiratory assessment. The significance of this work lies in its potential to democratize advanced respiratory monitoring technologies, making them accessible to a wider population, including those in remote or underserved areas. Full article

This study developed a fibre-optic laser Doppler velocimetry sensor for use in opaque, high-temperature, and high-pressure fluid flows by inserting the fibre perpendicular to the main flow. The tip of the optical fibre was obliquely polished and chemically etched using a buffered hydrofluoric acid solution, and a reflective mirror was deposited on the surface of the oblique fibre tip. Based on the results of the verification test using the rotating annular open channel, the fabrication conditions of the fibre tip were optimized for measuring the lubricating oil flow. The flow velocity profiles in the engine’s oil flow of the lubrication system during engine bench testing were measured. These velocity profiles were influenced by variations in the measurement position, oil temperature, and engine speed. The measurement accuracy of this sensor was compared with the volumetric flow rate obtained by cross-sectional area integration of the flow velocity profile, as measured using a Coriolis flowmeter, and the difference was within 1%. By combining computational simulation for flow and optical attenuation and particle scattering in light transmission through a working fluid, this fibre-optic sensor achieved a measurement volume of 200 microns in length and 200 microns in width at a distance of 900–1000 microns from the sensor. Full article

This study describes the implementation of Internet of Things (IoT) sensors in flow meters installed in drinking water systems and in fog catchers built in low-income, high-altitude communities in the Andes region of Ecuador, taking studies at the University de las Fuerzas Armadas ESPE as our reference. The influence and management of these intelligent sensors are analyzed, as well as a basic review of the materials and methods used in their implementation. The importance of validating the accuracy and reliability of IoT sensors compared to professional devices is highlighted, especially in mountain areas with difficult access. Additionally, the cost–benefit of using IoT sensors in fog catchers and drinking water distribution networks is mentioned, which depends on several factors such as the scale of the project, the objectives to be achieved concerning monitoring, and the available resources. Finally, it is highlighted that using Internet of Things (IoT) sensors in construction and water collection systems has proven beneficial in detecting possible effects on its operation and determining consumption and supply flows for a given population. Full article

During the drilling of ultra-deep wells, gas kick often occurs, influenced by the complex void pressure profile. The accurate description of particle settling behavior in the gas–liquid mixture is of great significance to effectively deal with gas kicks and ensure drilling safety. In this study, the gas–liquid two-phase annulus flow with different gas volume fractions is created through the transparent annular pipe, constant pressure air pump, and gas flowmeter. High-speed photography is used to record and analyze the sedimentation of particles in gas–liquid mixtures. This study is based on 288 tests. The main parameters in this experiment include the particle Reynolds number, the gas fraction, and liquid viscosity. The effects of wall and gas fraction on the drag coefficient were analyzed. The correlation of particle terminal settling velocity was established. The results obtained show a correlation with average absolute errors (AAE) of 10.7%. This study reveals the settling characteristics of particles in the annular gas–liquid mixed flow, provides an accurate terminal settling velocity prediction explicit formula, and provides guidance for the calculation of bottom hole pressure under the condition of gas kick. Full article

This study examines the impact of axial clearance variations on the performance characteristics of a dual-rotor flowmeter (DRT-FM) through numerical simulations, with the validity of the numerical results verified by calibration experiments. The results indicate that within the range of 200 L/h to 1600 L/h, the K factors of different groups increase as clearance increases. The K factor of the 0.80 mm group is the largest, showing an average increase of around 6% compared to that of the 0.50 mm group. Additionally, Linearity E also decreased, with a minimum of 1.07% in the 0.65 mm group, significantly lower than the 3.33% in the 0.50 mm group. Furthermore, the pressure loss increased slightly, with the 0.65 mm group having the largest pressure loss; however, at a flow rate of 1600 L/h, the pressure loss only increases by 0.186 kPa compared to that of the 0.50 mm group. Flow field analysis reveals that changes in axial clearance predominantly affect pressure distribution. Larger clearances reduce low-pressure regions on upstream and downstream transition surfaces, thereby reducing energy loss due to pressure changes. Entropy analysis further demonstrates that higher axial clearance decreases energy loss in the upstream and downstream stationary domains, optimizing the DRT-FM’s energy characteristics. Full article

Flow meters are extensively utilized in fields such as chemical engineering, petroleum, and aerospace, and are an indispensable component of modern industry. This paper examines the metrological properties of a dual-rotor turbine flow meter within its measurable flow range through experimental approaches and investigates the cavitation flow dynamics within the flow meter using numerical methods. First, the flow characteristics curve of the dual-rotor turbine flow meter was established experimentally, and the accuracy of numerical simulation results was validated. Secondly, the transient characteristics of the cavitation cavity were revealed using the Z-G-B cavitation model and dynamic mesh technology. Finally, entropy production theory was applied to investigate the energy losses caused by cavitation, analyzing the contributions of different types of energy losses during the cavitation process. Flow calibration experiments and numerical simulations reveal an increase in the meter coefficient of the dual-rotor turbine flow meter in high-flow cavitation zones, indicating that the displayed flow rate is slightly higher during cavitation compared to non-cavitating flows. Transient cavitation flow undergoes three stages: attachment, development, and collapse. At 323 K, the volume fractions of upstream and downstream cavities increase by 38.9% and 48.3%, respectively, with the cavitation cycle duration being 1.21 times that at 298 K. At 343 K, these increases are 75.3% and 239.2%, with the cycle duration being 2.63 times that at 298 K. Among the various sources of loss, the contribution from losses due to pulsating velocity gradients is the most significant, with maximum proportions of 81.95%, 85.1%, and 87.11% at 298 K, 323 K, and 343 K, respectively. Full article

To design the two-dimensional structural parameters of the core throttling component, i.e., the perforated plate for a liquid nitrogen (LN₂) balanced flowmeter, this paper presented an orthogonal experiment scheme with three parameters, three factors, and three interactions, combined with the three-dimensional CFD numerical simulation. The constructed mixture multi-phase flow numerical model considers the complex cavitation effect of LN₂ with a thermal effect. A DN40 balanced flowmeter and an LN₂ flowrate test setup based on a standard flowmeter were constructed, and the measured flowrate data were used to evaluate the CFD model. Based on the optimized two-dimensional structure and the validated numerical model, the influence of the three-dimensional thickness of the perforated plate on the flow and pressure drop coefficient was investigated. It was found that there are two throttling forms as the thickness increases, resulting in two pressure-changing characteristics. The formation mechanism was explained by analyzing the turbulence intensity distribution. Finally, the final flow coefficient, pressure drop coefficient, and upper limit of measurement due to the cavitation were analyzed and obtained. The results provide a feasible parameter design method for the cryogenic balanced flow meters. Full article

Large animals are increasingly used as experimental models of respiratory diseases. Precise characterization of respiratory mechanics requires dedicated equipment with specific characteristics which are difficult to find together in the same commercial device. In this work, we describe building and validation of a computer-controlled ventilator able to perform rapid airways occlusions during constant flow inflations followed by a prolonged inspiratory hold. A constant airflow is provided by a high pressure source (5 atm) connected to the breathing circuit by three proportional valves. The combined action of three 2-way valves produces the phases of the breath. During non-inspiratory breath phases, airflow is diverted to a flowmeter for precise feedback regulation of the proportional valves. A computer interface enables the user to change the breathing pattern, trigger test breaths or run predetermined breaths sequences. A respiratory system model was used to test the ability of the ventilator to correctly estimate interrupter resistance. The ventilator was able to produce a wide range of constant flows (0.1–1.6 L/s) with the selected timing. Errors in the measurement of interrupter resistance were small (1 ± 5% of the reference value). The device described reliably estimated interrupter resistance and can be useful as a measuring tool in large animal research. Full article

Centrifugal pumps are essential in many industrial processes. An accurate operation diagnosis of centrifugal pumps is crucial to ensure their reliable operation and extend their useful life. In real industry applications, many centrifugal pumps lack flowmeters and accurate pressure sensors, and therefore, it is not possible to determine whether the pump is operating near its best efficiency point (BEP). This paper investigates the detection of off-design operation and cavitation for centrifugal pumps with accelerometers and current sensors. To this end, a centrifugal pump was tested under off-design conditions and various levels of cavitation. A three-axis accelerometer and three Hall-effect current sensors were used to collect vibration and stator current signals simultaneously under each state. Both kinds of signals were evaluated for their effectiveness in operation diagnosis. Signal processing methods, including wavelet threshold function, variational mode decomposition (VMD), Park vector modulus transformation, and a marginal spectrum were introduced for feature extraction. Seven families of machine learning-based classification algorithms were evaluated for their performance when used for off-design and cavitation identification. The obtained results, using both types of signals, prove the effectiveness of both approaches and the advantages of combining them in achieving the most reliable operation diagnosis results for centrifugal pumps. Full article