Pressure Measurement System Research Articles

A study on the balance ability and plantar pressure of sarcopenia patients in different standing postures.

Sarcopenia usually manifests as a decrease in muscle mass and strength, seriously affecting the quality of life and independent living ability of elderly people. Moreover, sarcopenia is associated with various adverse outcomes such as mortality, postoperative infections, and severe complications, as well as affecting the balance and plantar pressure of the elderly. What are the characteristics of balance ability and plantar pressure in sarcopenia population across different standing postures? A plantar pressure measurement system was used to measure the COP parameters and plantar pressure of 70 individuals in four standing postures: Feet 10 cm apart (FA), Feet together (FT), Feet Semi Tandem (FST), and Feet Full Tandem (FFT). The plantar area was divided into ten regions based on the anatomical structure of the foot. An independent samples t-test was conducted for significance testing, and developed sarcopenia screening models based on binary logistic regression. Research has found that there are significant differences in the center of plantar pressure (COP) speed, 95 % elliptical region, COP length, and short axis length between populations with and without sarcopenia in the FST stance. The analysis of plantar pressure showed that the main differences between the two groups were located in the metatarsal and heel regions, and the accuracy of the binary logistic regression model constructed based on the FFT stance plantar pressure data without weight-adjusted for screening sarcopenia was as high as 94.3 %, which was superior to other standing postures. The difference in balance ability between sarcopenia population and non-sarcopenia population is reflected in standing posture with a relatively narrower base of support on the plantar surface (FST), and FFT stance plantar pressure can be used as a new method for screening sarcopenia.

Experimental study on the unsteady characteristics of flow evolution for two vehicles with ventilated partial cavitation

The object of this article is two parallel underwater vehicles with ventilated partial cavitation, which results in partial deformation of the ventilated cavity and is accompanied by nonlinear changes in the internal flow structure. In our experiments, a high-speed camera system was used to observe transient cavity evolution, and dynamic pressure measurement systems were employed to measure pressure fluctuations under different ventilation flow rates and parallel distances. The results indicated that cavity evolution goes through three stages after ventilation begins: the growth stage, the shortening stage, and the periodic shedding stage, with their periods being influenced by different variables. The dominant frequencies of grayscale variation in the three stages are significantly different, as are the pressure variations. Moreover, the dominant frequency of periodic shedding in the two cavities decreases as ventilation flow rates increase. A critical distance of d* = 1.6 was identified under the experimental conditions, which differentiates the pressure fluctuation characteristics at different parallel distances. Furthermore, the two main mechanisms of pressure fluctuation during the periodic shedding stage were clarified.

MATHEMATICAL MODELING OF THE DYNAMICS OF THE AEROELASTIC "PIPELINE – PRESSURE SENSOR" SYSTEM

This paper proposes mathematical models of mechanical systems "pipeline - pressure sensor" designed to control the pressure of the working medium in the combustion chambers of engines. In such systems, to mitigate the impact of vibration accelerations and high temperatures, the sensor is connected to the engine using a pipeline and is located at some distance from it. The movement of the working medium is described by linear models of fluid and gas mechanics. To describe the dynamics of an elastic sensitive element, linear models of the mechanics of a solid deformable body are used. Based on linear differential equations with partial derivatives, mathematical formulations of problems are proposed that correspond to three-dimensional models of pressure measurement systems in gas-liquid media for some pipeline cross-sectional shapes, namely, for a pipeline with a rectangular cross-section, with a section in the form of a sector and in the form of a ring. By introducing integral characteristics, the solution of problems is reduced to studying one-dimensional models. Equations have been obtained that make it possible to determine the pressure of the working medium in the combustion chamber at each moment of time by the value of deformation of the sensitive element of the sensor. Analytical and numerical-analytical methods for solving the corresponding initial-boundary value problems for systems of differential equations are proposed. In the analytical approach, the solution of the problem is reduced to solving a differential equation with a deviating argument. The numerical-analytical study of the problem is based on the application of the Galerkin method. Also, a numerical experiment was carried out and examples of calculating the deformation of the sensitive element of the sensor in the case of rigid fastening when specifying specific values of the mechanical parameters of the system are presented, also during setting the law of change in the excess pressure of the working medium in the engine.

LOad Monitoring and Intervention System (LOMIS) to prevent diabetic foot ulceration: Study protocol for a multi-phased safety and performance evaluation of a novel medical device

Background Plantar foot pressure is a significant risk factor for ulceration in diabetic feet. However, foot pressure-based ulceration risk prediction has remained confined to the contribution of compressive pressure measured under controlled laboratory conditions for more than 30 years. This ignores the strong evidence that two important shear pressures are critical for tissue damage and ulceration genesis. It also prevents the cumulative effect of free-living behaviors on compressive and shear pressures from being integrated into predictive models of ulceration risk, and therefore risk prediction in real time. To address these fundamental limitations, the primary objective of this study was to assess the functionality of a novel LOMIS insole device that measures both shear and compressive pressure during daily activities over extended periods. The secondary objectives include assessing safety, validity, suitability, and feasibility as a clinical intervention. Methods Eighty patients with diabetes (aged 18–85 years, with feet classified as low, moderate, or high risk of ulceration) recruited from three clinical sites. Phase one includes a controlled walking assessment in the laboratory; Phase 2 pilots the device during participants’ free-living activities over five days, and phase three extends this to a three-month longitudinal study of compressive and shear pressure under real-life conditions. Discussion This is the first multi-center pilot study of a novel in-shoe pressure and shear measurement system that aimed to continuously measure the risk of foot ulceration. Through iterative testing to establish safety and functionality evidence, this study supports the development of digital healthcare technology and predictive foot ulceration risk models based on free-living data. Testing the feasibility and functionality of the LOMIS device in free-living circumstances will inform subsequent efficacy study designs and the pathway toward implementation in healthcare services. Trial registration ISRCTN87061146, Registered on 06/10/2022 https://www.isrctn.com/ISRCTN87061146 Protocol version 9, 12/02/2024

Characterization of aircraft landing impact loads: Effects on vertical tire-pavement contact characteristics and pavement performance

The comprehensive understanding of the mechanistic behavior of airport pavements under aircraft landing loads is essential for ensuring safety and durability. Addressing the limited understanding on the interaction between aircraft landing gear and airport pavement during landing, this study proposed a measurement method for the vertical dynamic contact characteristics of tire-pavement interface and internal dynamic responses based on a laboratory dynamic test device. This involved the experimental design and testing method for the dynamic characteristics of landing gear landing loads, utilizing the Tekscan pressure measurement system to evaluate the vertical dynamic contact characteristics between the aircraft tires and pavement during landing. Through comparative analysis with the static results, the study revealed the importance of landing load measurements for mechanical response analysis and durability design of airport pavements. Additionally, the study investigated the dynamic response of airport pavements under different simulated aircraft landing speeds and weights, and further quantified the impact effects of aircraft landing loads on airport pavements. The results show that the vertical tire-pavement contact characteristics under landing impact are significantly different from those under static conditions, and need to be considered. The proposed quantitative equations with acceptable good fitting effect provided more accurate and efficient vertical load inputs for numerical simulation and durability design of airport pavements, which laid the foundation for understanding the failure mechanisms of airport pavement and enhancing the safety of aircraft and airport operation.

Development of Non-Invasive Continuous Blood Pressure Measurement System Based on Multiple Feature Parameters

To address the issue of the difficulty in implementing non-invasive continuous blood pressure measurement technology in China, this study developed a high-performance synchronous electrocardiogram (ECG) and photoplethysmography (PPG) signal acquisition system. A PC-based human-computer interaction software platform was constructed, and continuous blood pressure measurement-related algorithms were integrated. Multiple feature parameters such as pulse wave transit time based on synchronous ECG and PPG signals were extracted, enabling non-invasive continuous blood pressure measurement. To verify the measurement accuracy of the system, tests and comparative verifications were carried out. The results demonstrated that the system could meet the requirements of relevant standards and have good application value.

Identifying the frequency characteristics of the pressure measurement system with a pressure transmission tube using shock tube method

The identification of the frequency characteristics of the pressure measurement system with a pressure transmission tube is inevitably affected by the structure size, the transfer model, and complex noise interferences, which limits the achievable accuracy of the dynamic pressure measurements in some special conditions, such as narrow installation space and high temperature environments. This paper proposes a data-driven calibration method for identifying the frequency characteristics of pressure measurement system with a pressure transmission tube by shock tube system. The distorted calibration signal is first corrected to reduce the effect of complex noise by combining the robust local mean decomposition and a main frequency dispersion component cluster scheme. A modified Levenberg-Marquardt algorithm is presented to establish the transfer model of the pressure measurement system based on the corrected calibration signal and the dynamic pressure generated by shock tube. The frequency characteristics of the pressure measurement system is then identified, and the dispersion of the calibration results is quantitatively evaluated through a kernel density estimation assisted Monte Carlo method. A series of calibration experiments for pressure measurement system with pressure transmission tubes are carried out by a shock tube system. Results show that the proposed method is able to reduce the influence of high-frequency noise and improve the calibration results of the multiple frequency characteristics of the pressure measurement system with a pressure transmission tube. Furthermore, the comparative experiments on the dispersion evaluation of calibration results also demonstrate the superiority of the proposed method over the Fourier transformation method in calibration reliability.

Optimization of Centrifugal Pump Properties to Improve the Accuracy of Water Discharge and Pump Head Measurements

Centrifugal pumps are extensively used in industries and water management systems, where accurate measurements of water flow rate and pump head are essential for evaluating performance. However, inaccuracies arising from suboptimal designs of training kits present challenges in educational environments. This study aimed to optimize a centrifugal pump training kit to enhance measurement accuracy and reliability. The research was conducted over four months, involving modifications to the impeller, casing, and pressure measurement systems, along with rigorous calibration to minimize errors. Measurements of suction pressure, discharge pressure, water flow rate, and pump head were repeated under standardized conditions to ensure data consistency. The results demonstrated significant improvements, with consistent measurements of suction pressure (21 inHg), discharge pressure (15 PSI), water flow rate (0.5 L/s), and pump head (1.38 mH₂O). These optimizations reduced system inefficiencies, such as backflow and turbulence, and enhanced the kit’s ability to replicate real-world operating conditions. The improved training kit provides students with a reliable tool for practical learning, bridging theoretical concepts with real-world applications in fluid mechanics. This study underscores the importance of continual enhancement of laboratory teaching tools to support effective education and industrial relevance.

Functional Monitoring of Patients With Knee Osteoarthritis Based on Multidimensional Wearable Plantar Pressure Features: Cross-Sectional Study.

Patients with knee osteoarthritis (KOA) often present lower extremity motor dysfunction. However, traditional radiography is a static assessment and cannot achieve long-term dynamic functional monitoring. Plantar pressure signals have demonstrated potential applications in the diagnosis and rehabilitation monitoring of KOA. Through wearable gait analysis technology, we aim to obtain abundant gait information based on machine learning techniques to develop a simple, rapid, effective, and patient-friendly functional assessment model for the KOA rehabilitation process to provide long-term remote monitoring, which is conducive to reducing the burden of social health care system. This cross-sectional study enrolled patients diagnosed with KOA who were able to walk independently for 2 minutes. Participants were given clinically recommended functional tests, including the 40-m fast-paced walk test (40mFPWT) and timed up-and-go test (TUGT). We used a smart shoe system to gather gait pressure data from patients with KOA. The multidimensional gait features extracted from the data and physical characteristics were used to establish the KOA functional feature database for the plantar pressure measurement system. 40mFPWT and TUGT regression prediction models were trained using a series of mature machine learning algorithms. Furthermore, model stacking and average ensemble learning methods were adopted to further improve the generalization performance of the model. Mean absolute error (MAE), mean absolute percentage error (MAPE), and root mean squared error (RMSE) were used as regression performance metrics to evaluate the results of different models. A total of 92 patients with KOA were included, exhibiting varying degrees of severity as evaluated by the Kellgren and Lawrence classification. A total of 380 gait features and 4 physical characteristics were extracted to form the feature database. Effective stepwise feature selection determined optimal feature subsets of 11 variables for the 40mFPWT and 10 variables for the TUGT. Among all models, the weighted average ensemble model using 4 tree-based models had the best generalization performance in the test set, with an MAE of 2.686 seconds, MAPE of 9.602%, and RMSE of 3.316 seconds for the prediction of the 40mFPWT and an MAE of 1.280 seconds, MAPE of 12.389%, and RMSE of 1.905 seconds for the prediction of the TUGT. This wearable plantar pressure feature technique can objectively quantify indicators that reflect functional status and is promising as a new tool for long-term remote functional monitoring of patients with KOA. Future work is needed to further explore and investigate the relationship between gait characteristics and functional status with more functional tests and in larger sample cohorts.

Effect of the External Pressure on Li-Ion Pouch Cell at High C-Rate Conditions

Rechargeable Lithium-ion batteries (LIBs) are the power source used widely in portable electronic devices and are becoming increasingly important in the automotive industry applications. LIBs need to be high-energy, safe, and cost-effective to address the demand for large driving ranges of batteries in electric vehicles (EVs) and hybrid electric vehicles (HEV). Therefore, technologies for extending the cycle life of LIBs and solving component degradation problems are required. Recently, the recharging time for batteries in EVs is longer compared to the refueling time for gasoline-powered vehicles which prevents the widespread adoption of battery-powered EVs into the transportation sector. In that perspective, achieving fast charge has been considered as one of the most important directions for the progression of EVs in the market and it can possibly lead to increased customer acceptability by reducing charging time. However, fast charging of LIBs makes them susceptible to lithium plating and induces high temperatures, and the decomposition of electrolytes results in thermal runaway and explosion. Thus, understanding capacity fades and improving cell stability for long cycle life at a high C-rate are critical for designing LIBs. It has been known that external pressure has a positive influence on Li-ion pouch cell capacity fading during aging experiments. Nonetheless, the effect of external pressure under high C-rate conditions is not well understood and has not been extensively covered in many studies. Even in some of the research conducted experiments under high C-rate conditions, the concept of normalized capacity has been introduced, leading to studies that do not account for the initial capacity drop [1,2].This work analyzed the effect of external pressure on the battery’s sustainability under high C-rate conditions. The interrelationship of mechanical pressure and the electrochemical performance was investigated using 1.05 Ah graphite/NMC622 stacked LIBs. The charging speed was set to 1,5 and 10C-rates in the constant current/constant voltage (CC-CV) mode to test fast charging conditions. The pressure and thickness changes were analyzed using the pressure measurement system and 3-dimensional digital image correlation (3D-DIC). Also, the post-mortem analysis conducted to confirm the morphology of each cell component and internal resistance under fast charging conditions were analyzed using scanning electron microscopy (SEM) analysis and electrochemical impedance spectroscopy (EIS), respectively. The results demonstrate the negative influence of the external pressure was confirmed initial cycling stage increases the internal resistance which lowers the ionic conductivity. Overall, we propose that innovative pressurizing strategies to maximize cell cyclability and pressure sensing results could provide a non-destructive diagnostic approach to support the advancement of fast-charging battery technologies. This research highlights the significance of external active pressurization in systems operating at high C-rates. Reference [1] Mussa, A.S., et al., Effects of external pressure on the performance and ageing of single-layer lithium-ion pouch cells. Journal of Power sources, 2018. 385: p. 18-26[2] Chen, F., et al., Air and PCM cooling for battery thermal management considering battery cycle life. Applied Thermal Engineering, 2020. 173: p. 115154 Figure 1

Monte Carlo uncertainty quantification method of pneumatic measurement tube frequency response

Abstract The pneumatic tube plays a critical role in the frequency response of the pressure measurement system, which also greatly affects the accuracy of the measurement data. This paper applied the Monte Carlo uncertainty qualification method to the pressure measurement tube system frequency response and studied the effects of four parameters, including tube length, radius, temperature, and source pressure, on uncertainty characteristics for a given tube system configuration. The reported results show the technique's applicability and flexibility and the limitations of GUM. It is found that the frequency response and corresponding uncertainty are not directly related to frequency but are closely related to the natural frequencies. Comparative experimental results show that the longer tube significantly reduces the system's natural frequencies and intensifies the phase lag. In addition, larger tube radius and source pressure result in larger amplitude response peaks. Closed to the natural frequencies, with the increase of the parameter, the uncertainties of frequency response value and the corresponding variation range increase for tube radius and source pressure while decreasing for temperature and tube length.

Clinical Validation of Non-invasive Simulation-Based Determination of Vascular Impedance, Wave Intensity, and Hydraulic Work in Patients Undergoing Transcatheter Aortic Valve Replacement.

The impact of Aortic Stenosis (AS) on the left ventricle (LV) extends beyond the influence of the pressure drop across the stenotic valve, but also includes the additional serial afterload imposed by the vascular system. Aortic input impedance is the gold standard for comprehensively studying the contribution of the vascular system to total myocardial afterload, but in the past measurement has been challenging arising from the need for invasive catheterization or specialized equipment to precisely record time-resolved blood pressure and flow signals. The goal of this work was to develop and validate a novel simulation-based method for determining aortic input impedance using only clinically available echocardiographic data and a simple blood pressure measurement. A simulation-based method to determine vascular impedance was developed using echocardiographic data and a brachial blood pressure measurement. Simulation-based impedance was compared to impedance calculated from echocardiographic flow data and pressure data from a non-invasive central pressure measurement device. In validation analysis comparing patient-specific simulation-based vascular impedance to non-invasively measured impedance, correlation between methods across a range of vascular parameters varied between R2=0.40 and 0.99. A tendency was seen toward underestimation of pressure waveforms in point-by-point comparison of measured and simulated waveforms with an overall mean difference of 4.01mmHg. Requiring only non-invasive clinical data that are widely available, simulation-based vascular impedance has the potential to allow for easier, more widespread, and larger-scale investigation of the effect of vascular impedance on total LV afterload.

Secondary measurement standard for calibration of dynamic pressure sensor to bridge the gap between existing static and dynamic standards

A secondary measurement standard filling the gap between the available static and dynamic standards was developed. The standard utilizes a quick-opening valve and bursting diaphragms to generate step-like pressures with amplitude of few kilopascals to 10 MPa and with frequency content from 10-2 Hz to 800 Hz. An important design feature of the developed standard lies in the usage of aluminium diaphragms, allowing short rise times and high frequency content. The standard is based on two reference sensors, calibrated statically and dynamically. The reference sensors showed a linear dynamic response in the intermediate frequency range and was in good agreement with the static calibration results. Therefore, extrapolation of shock tube results was implemented. To demonstrate the capabilities of the developed standard, three pressure measurement systems were characterized, and their respective dynamic response was calculated. The results show that the developed standard can provide calibration information that are not currently available.

Efficient use of the TM-2441 ambulatory blood pressure measurement device in patients with diabetes.

Ambulatory blood pressure monitoring (ABPM) requires automatic measurement and the use of a validated device, according to current guidelines and international standardization. The TM-2441 (A&D Co. Ltd, Tokyo, Japan) ABPM device is small, lightweight, and suitable for use in ambulatory settings. It was validated against the ISO 81060-2:2013 standard in the general population. This study investigated the reliability of the ABPM device for patients with type 2 diabetes. Individuals aged more than 12 years affected with type 2 diabetes were recruited by our outpatient clinic. The blood pressure assessment was performed using the opposite limb simultaneous measurement according to the updated ISO 81060-2:2018. Forty-five subjects were included in the clinical investigation. The mean difference between blood pressure values measured by the TM-2441 ABPM device and the reference sphygmomanometer was within limits allowed by the ISO standard. Bland-Altman plots of the measurements and differences between the values obtained from the study device and those from the reference device showed no systematic variations in error. It was not possible to perform a stress test in most patients due to refusal or poor physical condition. The TM-2441 ABPM device fulfilled all the requirements of the ISO standard for ambulatory testing not only in a general population but also in the subgroup of subjects with type 2 diabetes.

Assessment of appropriate utilization of out-of-office diagnostic tools for the diagnosis of hypertension.

Out-of-office blood pressure (BP) measurement devices, such as ambulatory BP monitoring (ABPM) and home BP monitoring (HBPM), enhance the accuracy and reliability of BP readings, detecting white-coat and masked hypertension. The American Heart Association (AHA) advises confirming hypertension diagnoses with ABPM to prevent overdiagnosis, emphasizing the importance of precise out-of-office diagnostic tools. This study aimed to 1) explore the prevalence of ABPM and HBPM use prior to hypertension diagnosis; 2) assess the adherence to AHA recommendations regarding ABPM utilization; and 3) investigate the association between patient characteristics and out-of-office BP monitoring practices. A retrospective cross-sectional study analyzed a random sample of adult patients newly diagnosed with essential hypertension at a tertiary hospital primary care center in Riyadh, Saudi Arabia, between 2016 and 2022. This study evaluated the use of ABPM and HBPM in a sample of 268 newly diagnosed hypertensive patients, with a mean age of 49.17 ± 12.69 years. Although ABPM orders were placed for 57.8% of patients, only 48.5% completed the procedure. Notably, 42.2% of hypertension diagnoses were solely based on ABPM, while 7.1% and 1.1% utilized HBPM alone or in combination with ABPM, respectively. This analysis revealed a lower utilization of ABPM among older adults, individuals with diabetes or chronic kidney disease, and married patients (P < 0.05). However, this association with marital status, diabetes, and chronic kidney disease was no longer statistically significant in a fully adjusted model (P > 0.05). Out-of-office BP monitoring, particularly ABPM, was underutilized in newly diagnosed hypertensive patients, especially in older age groups and patients with specific comorbidities, who may benefit the most from this method. These results underscore the need for increasing physician knowledge and compliance with the existing guidelines.

Experimental study on effect of elastic-rigid composite boundary on shockwave from cavitation bubble collapse

Understanding the mechanisms behind the cavitation erosion resistance of elastic materials is the basis for the development of new cavitation erosion resistance materials. This paper employs underwater low-voltage discharge to induce cavitation bubble, combined with high-speed photography, shadowgraph methods, and transient pressure measurement systems to experimentally investigate the evolution and intensity of shockwave from bubble collapse near elastic-rigid composite boundary. Under the condition of constant elastic material thickness, with the bubble–wall distance increasing, shockwave shape evolves from multi-layers to single-layer. The peak pressure of the shockwave shows a trend of decreasing, then increasing, and finally stabilizing with increase in the bubble–wall distance. Furthermore, it was found that the elastic-rigid composite boundary causes the shockwave to reflect twice. As the material thickness increases, the intensity of the first reflected shockwave from the elastic surface decreases initially, then increases, and eventually stabilizes. However, that of the second reflected shockwave decreases. The total energy of the two reflections at the elastic interface is less than 4% of the mechanical energy of the bubble at its maximum volume. Finally, after the energy dissipation by the two reflections and material deformation, the elastic layer substrate withstands over 70% of the total mechanical energy of the cavitation bubble. There is an optimal elastic material thickness to minimize the shockwave load on the elastic layer substrate under the condition that the elastic-rigid composite boundary does not affect the evolution of cavitation bubble shape. These findings are significant for understanding bubble dynamics near elastic-rigid composite boundaries and provide theoretical support for developing cavitation erosion-resistant materials in engineering.

Measurement and analysis of photoacoustic pressure induced by weak microsecond pulsed light.

The photoacoustic effect (PAE) of weak microsecond pulsed light (WMPL) has immense potential for application to biomedical engineering. However, practical measurements and theoretical analysis of the photoacoustic pressure of WMPL are lacking. Hence, we constructed a WMPL photoacoustic pressure measurement system using an electret piezoelectric sensor and multi-wavelength parameter-adjustable pulsed light generator. Based on the system, the photoacoustic pressure interacting with the air medium induced by the WMPL with different optical parameters was measured. The measured pressure data were analyzed using the fixed variable method, and the pressure response characteristic was obtained. It was found that the measured results conform to the law of energy conversion but have a specific trend for some wavelengths. The analysis and discussion were conducted based on the classical wave equation of the PAE, and the extended wave equation was presented. It is shown that the proposed approach provides a reliable basis for the measurement and analysis of WMPL photoacoustic pressure.

Equilibrio y carga plantar en diferentes técnicas de sentadilla

This research aims to analyze dynamic balance and plantar load in different squatting techniques, providing insights into the influence of these exercises in practitioners who incorporate weightlifting into their training routines. A sample of 21 subjects engaged in activities involving three squatting techniques: Back Squat (BS), Front Squat (FS), and Overhead Squat (OHS) was analyzed. Participants assumed a baseline posture and performed exercises with approximately 50% RM for each squatting technique. A plantar pressure measurement system was used to assess center of pressure (COP) displacement, peak pressure (PP), and plantar load in different regions of the foot. One-way Welch's ANOVA considering COP displacement, PP, and percentage of force for each foot region was measured. The results showed no significant effect of the squatting technique on COP trajectory during the exercises. However, a significant interaction was observed between the squatting technique and PP compared to the static balance situation. All three squats resulted in higher PP than static balance, with OHS exhibiting the highest values, followed by FS and BS. No significant differences were found between the squat techniques. These findings suggest that different squat techniques can influence plantar load, but do not affect the trajectory of the COP during the execution of the exercise. The heel region generated the greatest plantar load among the three squat techniques and should receive greater attention during the squat and its variations. This information can assist in prescribing exercises and developing more efficient training programs for weightlifters.

Fiber Bragg Grating-based sensor for measuring supersonic inlet terminal shock at different angles of attack

This study presents a multipoint pressure measurement system using fiber Bragg grating sensors to detect terminal shock positions. The system consisted of a fiber optic string encapsulated with multiple diaphragm-based fiber Bragg grating sensors, capable of detecting flow field characteristics at fourteen different axial positions of the inlet. The calibration results indicated a sensitivity of 46.47 pm/kPa, a linear correlation coefficient of 0.9997, and a maximum repeatability error below 1.44%. In supersonic wind tunnel tests, the system effectively measured pressure and located the terminal shock across varying angles of attack and throttling degrees. The maximum difference compared to conventional pressure sensors was 4.7%, and the terminal shock positioning error was limited to 1.2%. Overall, the system has robust multipoint measurement capabilities and is priced at only one-tenth of traditional sensors, showing great potential in the field of inlet measurements.

On the acceptance limits for short-term level fluctuation of sound calibrators

To ensure noise measurement accuracy, sound calibrators are used to check the sound level meter accuracy before and after any such measurements, as required by most noise regulations. The sound calibrator itself needs to be calibrated routinely and traceable to national standards. The International Standard IEC 60942, Electroacoustics - Sound calibrators, specifies performance requirements for the sound pressure level, short-term level fluctuation, frequency, and distortion and associated test methods. However, the acceptance limits for short-term level fluctuation specified in IEC 60942 is problematic. The short-term level fluctuation acceptance limits specified in Table 2 of IEC 60942 for the level variations inherited by a stable sinusoid at low frequencies are either underestimated or overestimated. In this paper, a detailed theoretical analysis is presented addressing this particular issue. Closed-form solutions are obtained for typical sinusoidal sound signals. Two experimental setups and measurement results for the validation of the theoretical analysis are also presented. One uses a commercial sound level meter and the other uses a precision sound pressure measurement system developed recently at the National Research Council Canada. A revised table for the acceptance limits is then proposed for the future revision of Table 2 of IEC 60942.