Sensitivity of Piezoresistive Pressure Sensors to Acceleration

The article presents the negative aspects of the influence of static and dynamic acceleration on the accuracy of pressure measurement for a selected type of transmitter. The influence of static accelerations from catalog notes was shown and compared with the tests results for a few selected sensors. The results of research on the influence of dynamic acceleration for various types of its variability for selected converters are presented. Moreover, a method of measurement patented by the authors that uses a complex transducer is shown. The method allows for more accurate measurements on moving objects. The tests were performed based on the proposed method. The obtained results of the influence of acceleration on the classical sensor as well as the construction using the proposed method are shown. The paper presents approximate pressure measurement errors resulting from the influence of acceleration. For example, errors in measuring the speed of an airplane may occur without the proposed method. The last part of the article presents a unique design dedicated to a multi-point pressure measurement system, which uses the presented method of eliminating the influence of accelerations on the pressure measurement.

Evaluation of Picker Discomfort and Its Impact on Maintaining Strawberry Picking Quality

In this paper, the authors present the relationship between the assumptions of ergonomics in the work of a strawberry picker and quality of picked fruit. The body posture that a person adopts while working has a significant impact on their health, working comfort, and productivity, but also on the quality of the fruit that is harvested. This paper identifies three characteristic picker positions during strawberry harvesting. A synchronized surface electromyography (sEMG) instrument together with the Tekscan® surface pressure measurement system allowed for the determination of the influence of working position on changes in the load of the picker’s musculoskeletal system and the surface pressure exerted on the fruit during manual strawberry picking, which are decisive factors for maintaining fruit quality. In addition, compression tests on whole strawberry fruit were carried out as a benchmark to evaluate and compare the maximum forces as well as the destructive pressures on the fruit. From the tests, we found that the most comfortable position of the worker’s body was determined along with the harvesting technique (position during work) that has the least negative effect on the quality of the harvested fruit. Consequently, the level of dynamic load on the worker was determined.

Development of a dynamic pressure standard of low amplitudes and frequencies.

The height of the gravitational wave is an influential magnitude in the estimation of its energy content, a very important parameter in the design of maritime structures such as piers and breakwaters, however, there are reasonable doubts among researchers regarding the quality of its measurement. The objective of the present work was to demonstrate that a stationary calibrated pressure transmitter allows the indirect calculation of the wave height with satisfactory accuracy despite the fact that it is a dynamic event as long as its frequency range is low, as is the case with the gravitational waves of the Costa Rican Central Pacific Ocean: between 0.05 Hz and 0.39 Hz. In the absence of a primary pattern of periodic pressure disturbances, an alternate path was developed based on the characterization of the parameters of the differential equation characteristic of a pressure measurement system in a shock tube prototype from normal shock wave theory and subsequent verification in a periodic disturbance generator that its attenuation and delay are practically negligible at the frequency of 0,1 Hz. The effect of the different geometry of the chamber of the pressure measurement system used in the sea was evaluated pneumatically by comparison with the dynamic pressure standard in the prototype of the periodic disturbance generator, while the effect of the compressibility of the fluid was evaluated in water in the wave channel of the Laboratory of Maritime Engineering, Rivers and Estuaries of the University of Costa Rica. The results show that the pressure measured from the least-squared adjustment coefficients of an electric current transmitter obtained by stationary calibration is acceptable to estimate the climatology of the gravitational wave characteristic of the Costa Rican Central Pacific Ocean with maximum errors of 136 mm in waves of height up to 1,4 m.

Development of IoT Based Cuffless Blood Pressure Measurement System

Hypertension, commonly known as high blood pressure, is a major concern for people globally and in Malaysia. The hypertensive patient must commute to the hospital visiting their physician regularly for blood pressure (BP) monitoring using a cuff-based device. The patient may feel uncomfortable and pain when the device inflates the cuff and tightens around the arm for a BP measurement. Hence, to overcome this problem, this paper proposed a cuffless BP measurement using pulse transit time (PTT). In this method, a delay time between the peak of Photoplethysmogram (PPG) signals at the fingertip and the earlobe were correlated with BP. These signals were transferred to a computer via Arduino uno microcontroller and analyzed by the MATLAB R2019a software. A preliminary result shows that the developed system is able to record PTT and display the estimated BP value on the ThingSpeak webpage and ThingView apps. With the IoT platform, the cuffless BP can be monitor remotely, and the results can be store on the cloud healthcare system for hypertensive management.

Effect of Walking Speeds on Complexity of Plantar Pressure Patterns

Various walking speeds may induce different responses on the plantar pressure patterns. Current methods used to analyze plantar pressure patterns are linear and ignore nonlinear features. The purpose of this study was to analyze the complexity of plantar pressure images after walking at various speeds using nonlinear bidimensional multiscale entropy (MSE2D). Twelve participants (age: 27.1 ± 5.8 years; height: 170.3 ± 10.0 cm; and weight: 63.5 ± 13.5 kg) were recruited for walking at three speeds (slow at 1.8 mph, moderate at 3.6 mph, and fast at 5.4 mph) for 20 minutes. A plantar pressure measurement system was used to measure plantar pressure patterns. Complexity index (CI), a summation of MSE2D from all time scales, was used to quantify the changes of complexity of plantar pressure images. The analysis of variance with repeated measures and Fisher’s least significant difference correction were used to examine the results of this study. The results showed that CI of plantar pressure images of 1.8 mph (1.780) was significantly lower compared with 3.6 (1.790) and 5.4 mph (1.792). The results also showed that CI significantly increased from the 1st min (1.780) to the 10th min (1.791) and 20th min (1.791) with slow walking (1.8 mph). Our results indicate that slow walking at 1.8 mph may not be good for postural control compared with moderate walking (3.6 mph) and fast walking (5.4 mph). This study demonstrates that bidimensional multiscale entropy is able to quantify complexity changes of plantar pressure images after different walking speeds.

OXIDIZER AND GAS-ENVIRONMENT EFFECTS ON AFTERBURNING REACTIONS AND EXPLOSION PERFORMANCES OF HMX-BASED THERMOBARIC EXPLOSIVES

In this paper, confined explosions of HMX-based thermobaric explosives containing oxidizers in a spherical chamber were studied by changing the type of the oxidizer and the oxygen concentration in the environment. Based on an in-house developed optical-electrical system, the optical radiation signals of Al2O3 during the afterburning reaction were recorded. The results show that aluminum particles (5.4 µm) were strongly dependent on the oxygen concentration in the environment. Increasing the oxygen concentration can prolong the oxidation duration of Al and enhance the optical radiation intensity of Al2O3. The optical radiation result for Al2O3 in O2 and air showed that aluminum particles (the mass fraction was 33 %) were not completely oxidized in the air, and the oxidation duration was 500–700 µs. Moreover, the pressure data of the blast waves was obtained using a pressure-measurement system. The results showed that an increase in the oxygen concentration of the explosive could further enhance the total impulse, especially an addition of KP (its mass fraction was 10 %) could increase the total impulse by about 9 %.