Physics experiments with internal or external sensors using self-made apps for the smartphone

INTRODUCTION Low-priced smartphones with physics sensors have become widespread. Anyone can easily use a smartphone as a measuring device for physics experiments anywhere, not just in school laboratories. If one can make self-made apps using the sensor built into the smartphone, it is also possible to build an original measuring device. We have therefore developed apps (“Diracma” series) with functions that are not available to public apps for physics experiments. WHY SELF-MADE APPS? Physics experiments using smartphone apps, which have been open to the public, have been reported. Using these smartphone apps, experiments can be performed not only in the laboratory but also in other locations. These public open apps are useful, but there were no apps with functions that we needed for specific experiments. For example, there was no function to convert acceleration data to velocity data immediately. Furthermore, there were also no functions to generate and record sound waves at the same time, and to connect an external sensor.  Therefore, we started to develop self-made apps to include the aforementioned functions and to make them easier to use since 2013. Using the practice cycle (see Fig. 1 in Abstract PDF), we have done a new scheme of physics education. APPS “DIRACMA” SERIES USING SENSORS The first app “Diracma 1” (current app “DiracmaA”) using an internal acceleration sensor was released to the public in 2015. There are several apps, which are “DiracmaS” for an internal audio sensor, and “DiracmaM” for an external sensor (Adachi, 2021). There is a possibility that these smartphone apps can be effectively used in online classes by using students’ smartphones. The “DiracmaM” app can connect an ultrasonic sensor unit to a smartphone by a USB cable and there are many related experiments for physics classes (the HP site, “Mobile Physics Education Lab” https://sites.google.com/view/diracma888/). This mobile ultrasonic sensor unit can be purchased from the “Mobile Education Lab”.  This sensor unit is inexpensive and ready to use in class. ACKNOWLEDGMENTS A part of this research was supported by the Japan Society for the Promotion of Science KAKENHI grant number JP17H00166, JP19H00087, and JP21K02954. We thank Prof. Murata, who was a president of the Physics Education Society of Japan, for fruitful discussion. REFERENCE Adachi, A. (2021). New Physics Experiments using Model Train and Smartphone Apps (Volume 1 Constant-Velocity Motion). Kindle Book https://www.amazon.com/dp/B08YD15NZX

Overcoming Failure of Synchronous Motor Driven Compressor Train by Application of Controlled Slip Clutch

Case StudyThis case study describes failure incident of a centrifugal compressor, its root cause investigation, and countermeasure implementation. An integrally geared centrifugal air compressor driven by a synchronous motor failed during its initial startup in a newly constructed petrochemical plant. Failure mechanism was identified as torsional resonance during synchronous motor’s startup with stronger torque amplification than the design intention. As a quick yet very effective solution to this problem, a clutch with controlled slip mechanism was applied. Torsional analysis reflecting the clutch mechanism as well as on-site strain gauge measurement verified its effectiveness. After implementation of this clutch, no malfunction or abnormality has been observed in the compressor train

Torsional Instability Of Cooling Tower Fan During Induction Motor Startup

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Prediction Of Lateral Vibration Behavior Of Integrally Geared Centrifugal Compressor During Synchronous Motor Startup By Transient Torsional-Lateral Coupled Analysis

LectureStartup transients of both torsional and lateral vibration behaviors of an integrally geared centrifugal compressor driven by a synchronous motor are examined by transient torsional-lateral coupled analyses, and the numerical calculation results are evaluated using the field measurements as a benchmark. Since linear bearing coefficients are employed in the numerical simulation instead of more sophisticated nonlinear bearing model, bilinear stiffness is additionally considered to reflect the effects of the rotor confinement within the bearing clearance. Moreover, temporary teeth separation of the gear meshing and engagement at the backside during torque reversal is also considered in the numerical calculation. The transient lateral vibration behavior of the pinion rotor during the synchronous motor’s startup is successfully replicated. Both (a) bilinear stiffness of the pinion rotor bearings due to rotor restraint within the bearing clearance, and (b) effect of temporary teeth separation within the backlash and engagement at the backside because of torque reversal, are found to strongly influence the numerical predictions