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Sensors ◽  
2021 ◽  
Vol 21 (20) ◽  
pp. 6804
Author(s):  
Sebastian Sławski ◽  
Marek Kciuk ◽  
Wojciech Klein

In this article, changes in NiTi alloy (Flexinol) electrical resistance during cyclic stretching with small elongation were investigated. A dedicated test stand consisting of motorized vertical test stand, force gauge, and electric resistance measuring device with an accuracy of 0.006 Ω was developed. A dedicated control algorithm was developed using LabVIEW software. Changes in electrical resistance were investigated for the 0.1 mm Flexinol wire with length of 120 mm. Testing was performed in the elongation range between 0.25% and 1.5% in martensite phase. Tested samples were subjected to 30 stretching cycles with a movement speed of 10 mm/min. Obtained results show that the cyclic stretching of Flexinol wire reduces its electrical resistance with each stretching cycle. Moreover, it was noted that changes in Flexinol electrical resistance during cycling stretching depend on the assumed elongation and number of the already performed stretching cycles. The observed electrical resistance change decreases with each stretching cycle. Thus, the observed changes are greater during the first stretching cycles. For elongations exceeding 1%, the Flexinol electrical resistance in the first stretching cycle increases. In each subsequent cycle, electrical resistance decreases, as in the case of the smallest value of assumed elongation. In almost all tested cases (except in the case with 1.5% of assumed elongation), Flexinol electrical resistance after 30 stretching cycles was smaller than before the test.


2021 ◽  
Vol Publish Ahead of Print ◽  
Author(s):  
Chihiro Yagi ◽  
Yuka Morita ◽  
Meiko Kitazawa ◽  
Yoriko Nonomura ◽  
Tatsuya Yamagishi ◽  
...  

Author(s):  
Jon Mikel Picabea ◽  
Jesús Cámara ◽  
Javier Yanci

The aims of this study were to: (1) analyze table tennis players’ physical profiles considering and comparing players age categories (i.e., under U12, U14, U16, U20, Senior and Older); and (2) to quantify the correlations among the variables measured by each test. Seventy-one table tennis players (61 men and 10 women, 19.7 ± 11.23 years, 1.65 ± 0.13 m, 59.71 ± 17.72 kg and 21.60 ± 4.22 kg/m2) divided into six age groups, performed a sprint test, forearm isometric strength test, countermovement vertical test, countermovement horizontal test, change of direction ability (CODA) test and flexibility test. U14 players performed better than U12 in all tests (ES = −0.70 to 1.98, moderate to large) except in Sit and Reach (SAR) test (ES = 0.19, trivial). The U16 group also obtained better results than U14 in all tests (ES = 0.77 to −2.31, moderate to large) except for the SAR test (ES = 0.19, trivial). The U20 group performed better than U16 in all the tests (ES = 0.73 to −1.53, moderate to large) except for the 5 m sprint test (ES = −0.02, trivial), 10 m sprint test (ES = −0.51, moderate) and SAR (ES = 0.11, trivial). Differences between Senior and U20 were only found in the arm swing counter movement jump (CMJAS) (ES = −0.82, large) and modified agility test (MAT) (ES = 1.19, large), with the U20 group being better in both variables. The senior group performed better in the MAT test than the older group (ES = 0.94, large). The relation found between forearm isometric strength, vertical jump, horizontal jump, sprint and CODA ability (r = −0.53; ±0.14, 0/0/100, most likely to r = 0.83; ±0.06, 100/0/0, most likely) indicates that these capacities are related in table tennis players. Nevertheless, the lack of association between the sit and reach test with the other capacities may indicate that flexibility is an independent capacity.


2021 ◽  
pp. 1-16
Author(s):  
Tarek Ganat ◽  
Meftah Hrairi ◽  
Raoof Gholami ◽  
Taha Abouargub ◽  
Eghbal Motaei

Liquid-liquid phase flow in pipes merits further investigation as a challenging issue that has very rich physics and is faced in everyday applications. It is the main problem challenging the fluid flow mechanism in the oil and gas industry. The pressure gradient of liquid flow and flow pattern are still the topics of numerous research projects. In this paper, the emphasis is on further investigation to research the flow pattern, water holdup (HW), and pressure decrease for vertical, horizontal, and inclined flow directions of oil and water flows. Test section lines of 4.19-in. (106.426 mm) inner diameter (ID) and 5-m horizontal, 5-m inclined, and 5-m vertical test sections were serially connected. The experiments were conducted at 40°C using 2-cp viscosity oil and tap water, and oil density of 850 kg/m3, at the standard conditions. Fifty experiments were executed at 250 kPa at the multiphase flow test facility, with horizontal, upward (0.6° and 4°), downward (−0.6° and −4°) hilly terrain and vertical pipes. The oil and water superficial velocities were changed between 0.03 and 2 m/s. This evidence was obtained using video recordings; the flow patterns were observed, and the selection of each flow pattern was depicted for each condition. For horizontal and inclined flow, new flow patterns were documented (e.g., oil transfer in a line forms at the top of the pipeline, typically at high water rate, and water transfer at the lower part of the pipe at a high oil rate). The data were taken at each flow condition, resulting in new holdup and pressure drop. The results show that the flow rate and the pipe inclination angle have major impacts on the holdup and pressure drop performances. In the vertical flow, a clear peak was demonstrated by experiments after the superficial oil velocity reached a certain value. This peak is known as phase inversion point, where after this peak, the pressure starts declining as the superficial oil velocity increases. Also, slippage has been observed after varying inlet oil flow rates between the two phases. The experiments showed that with minor alteration in the inclination angle, the slippage was significantly changed. This study presented new experimental results (measured mainly at horizontal, inclined, and vertical flow conditions) of HW, flow pattern, and pressure drop. These findings are key evidence of the evolving oil-water and flowline estimate models.


2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Zhen Yu ◽  
Yuan Zhang

High-precision reducer is the core component of industrial robots. In order to achieve the comprehensive performance testing of precision reducers, an instrument with a vertical layout and a cylindrical structure is designed. As a rotating machine, the inevitable coupling misalignment of the instrument can lead to vibration faults which lead to errors in the test. So it is pretty necessary to diagnose and monitor the coupling misalignment while the instrument is working. The causes of the coupling misaligned fault of the instrument and the relationship between the misalignment fault and torque ripple are analyzed in this paper. A method of using the torque transducer in the measurement chain of the instrument to diagnose the coupling misalignment is proposed in this paper. Many experiments have been done to test the capability of detecting the coupling misalignment using this method. Experimental results show that the amplitude of torque ripple of the shaft is linearly related to the coupling misalignment and is quadratically related to the rotation speed of the shaft when the misalignment exists in the shaft. The combination of components at the rotation frequency (fr) and the additional components can be used to diagnose faults due to coupling misalignment.


2021 ◽  
Vol 2 (2) ◽  
pp. 015-023
Author(s):  
Irsyadi Yani ◽  
Amir Arifin ◽  
Ahmad Irham Jambak ◽  
Gunawan Gunawan ◽  
Dendy Adanta ◽  
...  

Formula Society of Automotive Engineers (FSAE) is a competition where the students design, build, and race the formula-style car. In this competition, the regulation stringent for the safety of participants. Chassis is one of the regulated parts among the other parts. This paper examines design process followed by chassis analysis by using Solidworks 2018 and Abaqus/CAE 6.14 software. The analysis process is carried out with Static Vertical Test, Torsional Stiffness Test, and Crash Impact Test using a safety standard in the form of a safety factor that must be more than 1 (SF> 1) to ensure the safety of the driver. The aim is to obtain an optimum final design based on FSAE Japan regulation as a reference for the Universitas Sriwijaya electric car team, namely Sriwijaya Eco in making the framework for the upcoming electric formula car.


2021 ◽  
pp. 1-7
Author(s):  
Laura Riera-Tur ◽  
Andres Caballero-Garcia ◽  
Antonio J. Martin-Mateos ◽  
Alfonso M. Lechuga-Sancho

BACKGROUND: The subjective visual vertical (SVV) test is a sensitive test of vestibular dysfunction that allows the evaluation of otolithic organs; however, with the current method, there are technical and logistical limitations that make the application of this test difficult in the conventional clinic. OBJECTIVE: The objective of this study is to assess the effectiveness of detecting vestibular pathology using the SVV via a new screening method. METHODS: A consecutive sample of 62 patients with suspected vestibular pathology was included in the study. The patients were clinically diagnosed according to the Barany Society criteria. An exploratory system was designed using a mobile application in Android that detects accelerometer oscillations and involves placing the smartphone on a rotating disk anchored to the wall. All patients underwent a SVV examination using the bucket method and the study test. A cut-off point of the ROC curve was calculated for each test, and its sensitivity, specificity, diagnostic accuracy and probability ratios for detecting vestibular pathology were analysed. The SVV results were compared using the bucket test and the study test. RESULTS: We observed significant differences in sensitivity between the two tests: 86.95% for the study test versus 67.4% for the bucket test (p <  0.01). In the ROC curve, an area under the curve of 0.90 was observed for the study test, with a cut-off of 2.43 for a sensitivity of 86.95% and a specificity of 93.75%. CONCLUSIONS: SVV testing using a smartphone placed on a rotating disk anchored to the wall offers greater diagnostic accuracy than SVV using the bucket test. Both methods are inexpensive, harmless and easily accepted by patients.


2021 ◽  
Vol 62 (6) ◽  
Author(s):  
Dominik Saile ◽  
Viktor Kühl ◽  
Ali Gülhan

Abstract Buffet/buffeting as load imposing mechanism on the base structures of space launcher has been of strong interest ever since it was found as partially responsible for the failed flight 157 of Ariane 5. Several studies suggested that the base region is most excited at Mach 0.8. A preceding study of the current series on base flow effects revealed a differing excitation in comparison to the other subsonic Mach number cases. It featured an especially pronounced excitation in the recirculation region. Thus, the current work attempts to answer the question why this case appears to be distinct. This is done by decreasing the relative nozzle length and focusing on the Reynolds stress distribution. The research question is approached by experiments in the ‘Vertical Test Section Cologne’ (VMK) on a base model with supersonic, over-expanded exhaust jet exposed to an ambient flow at Mach 0.8 and a Reynolds number of $$1.4\cdot 10^6$$ 1.4 · 10 6 . Data are acquired by means of particle image velocimetry (PIV) and high-speed schlieren imaging. The results reveal that a most unfavorable configuration appears to exist, which is if the mean shear layer reattachment takes place just on the tip of the nozzle. Graphic abstract


Retos ◽  
2021 ◽  
Vol 42 ◽  
pp. 612-617
Author(s):  
Matias Ruben López Ferrada ◽  
Fernando Javier Cerda Navarrete ◽  
Cristian José Oñate Navarrete ◽  
Roberto Lagos Hernandez

  El presente estudio transversal pretende determinar y establecer la asociación entre las variables de estado nutricional y fuerza en el segmento inferior entre estudiantes Chilenos correspondientes a la región de la Araucanía, pertenecientes a un sector urbano en contraste con estudiantes de un sector rural. La muestra fue de 120 escolares, divididos en 60 niños y 60 niñas cuyas edades fluctuaron entre los 10 y 11 años . Se realizó medición del IMC (Kg/H^2) para luego clasificar su estado nutricional y también la prueba de salto vertical Test de Sargent (fuerza de tren inferior) en la población escolar. Los grupos fueron comparados con la prueba estadística Chi-cuadrado con intervalos de confianza del 95 %. Para los resultados del test de Sargent se realizó correlación de Pearson. Se encontró una alta prevalencia de niñas de ambos sectores, encasilladas en el rango de sobrepeso y obesidad. Así mismo, presentan similitud en la prueba de salto vertical (test de Sargent) en donde no existieron diferencias significativas al momento de correlacionar entre sexo y área geográfica.  Abstact. The present cross-sectional study aims to determine an establish the association between the variables of nutritional status and lower segment in Chilean students from Araucanía Region an urban sector in contrast to students from a rural sector. The sample was 120 schoolchildren, divided into 60 boys and 60 girls whose ages fluctuated between 10 and 11 years of age. BMI (Kg / H ^ 2) was measured to later classify their nutritional status and also the Sargent vertical jump test (lower body strength) in the school population. The groups were compared with the statistical T-student test for independent samples with 95% confidence intervals. Pearson's correlation was performed for the results of the Sargent test. A high prevalence of girls from both sectors was found, classified as overweight and in the obesity range. Likewise, there are more overweight children in the urban sector than in the rural sector. Presenting similarity in the vertical jump test (Sargent test) where there were no significant differences when correlating between sex and geographic area.


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