Automated Analysis of the Two-Minute Walk Test in Clinical Practice Using Accelerometer Data

One of the core problems for people with multiple sclerosis (pwMS) is the impairment of their ability to walk, which can be severely restrictive in everyday life. Therefore, monitoring of ambulatory function is of great importance to be able to effectively counteract disease progression. An extensive gait analysis, such as the Dresden protocol for multidimensional walking assessment, covers several facets of walking impairment including a 2-min walk test, in which the distance taken by the patient in two minutes is measured by an odometer. Using this approach, it is questionable how precise the measuring methods are at recording the distance traveled. In this project, we investigate whether the current measurement can be replaced by a digital measurement method based on accelerometers (six Opal sensors from the Mobility Lab system) that are attached to the patient’s body. We developed two algorithms using these data and compared the validity of these approaches using the results from 2-min walk tests from 562 pwMS that were collected with a gold-standard odometer. In 48.4% of pwMS, we detected an average relative measurement error of less than 5%, while results from 25.8% of the pwMS showed a relative measurement error of up to 10%. The algorithm had difficulties correctly calculating the walking distances in another 25.8% of pwMS; these results showed a measurement error of more than 20%. A main reason for this moderate performance was the variety of pathologically altered gait patterns in pwMS that may complicate the step detection. Overall, both algorithms achieved favorable levels of agreement (r = 0.884 and r = 0.980) with the odometer. Finally, we present suggestions for improvement of the measurement system to be implemented in the future.

Evaluation of hull vibration reduction using multi-layer transom cover for outboard motor

The article discusses the results of experiments on measuring vibration of the hull of a small vessel using various methods of vibroinsulation of outboard motors SEA PRO (nominal capacity 5 h.p.) and SEA PRO (nominal capacity 2.5 h.p.). There have been recorded the harmful effects of prolonged exposure to vibration on the human body, as well as on the boat hull and outboard motor. The peak vibration level was measured and the effectiveness of different types of vibroinsulation was evaluated. The experiments were carried out using a vibrometer Ekofizika-110A made in Russia (relative measurement error ± 0.5 dB) and a vibrometer AR63A made in China (relative measurement error ± 5%). The illustrations of the vibrometers used are presented. It was determined that a multi-layer transom cover is a fairly effective way to reduce the vibration of the motor boat hull. The highest efficiency was achieved for the outboard motor SEA PRO 5.0 when it was running at full speed; a 17.3% reduction in vibration was recorded when using the relative value of vibration acceleration (dB). For the outboard motor SEA PRO 2.5 running at medium speed the decreased vibration (9.5%) was recorded when using the relative value of vibration acceleration (dB). The conclusion has been made about the prospects of reducing the vibration of outboard motors and the need for scientific and experimental research, as well as for the development of standards for permissible vibration of the motor boat hull, which can limit the harmful effect on the crew, the boat structure and the outboard motor. The formula of the logarithmic levels of vibration acceleration in relative units is given in accordance with generally accepted sanitary rules and regulations.

Simultaneous Verification of Multi-Ultrasonic-Flowmeters in Tandem Arrangement for Natural Gas

A combined experiment and numerical analysis was performed to determine whether the flow field has a significant impact on the simultaneous verification of multi-ultrasonic flowmeters (UFMs) in tandem arrangement (SVUFMST) and whether the SVUFMST is practical for flowrate measurement of pressurized natural gas. In practical testing, SVUFMST can highly improve the efficiency of UFMs’ calibration. Two types of UFMs of different nominal diameter were studied: DN250 and DN150. When it comes to DN250, data obtained from the actual-flow experiments were first used to verify the simulated results for n ≤ 3 (number of tested UFMs) and then the verified numerical method was extended to simulate the internal flow of four and five tested UFMs. Comparison analysis shows that all the numerical results agree remarkably well with the available experimental data and more than two tested UFMs can induce an overall shift in the E–Q curve (relative measurement error E plotted as a function of flowrate Q). For the slight difference among the tested UFMs, the practicability of the SVUFMST at n ≤ 4 (DN250) and n ≤ 3 (DN150) are thereby proved, whereas the striking difference in E (~1.0%) between the most downstream UFM and the other UFMs for n = 5 (DN250), associated with the outstanding collapse onto the velocity profile along the acoustic paths, results in the invalidation of the SVUFMST.

Dependence of the Correlation Coefficient Between the Results of a Parameter Measurement and Its True Values on the Reduced Measurement Error

Magnetic testing of steels' mechanical properties is based on their correlation with steels' magnetic parameters. The purpose of this work was to establish dependence of the attainable correlation coefficient Rmax between measurement results and the parameter values a on the reduced error of its measurement. The article proposes a model of the correlation field between the parameter true values and the results of its measurement with a given reduced error δ. The merits and legitimacy of using the model for estimation of the achievable correlation coefficient Rmax are substantiated. Analysis of influence of δ parameter measurement in different ranges d of its change on Rmax is carried out. Results are compared with the previous analysis for the relative measurement error. It has been established in this work that the coefficient Rmax calculated for the reduced measurement error is always smaller than Rmax one calculated for the relative measurement error. However in the practically important range of variation of d with δ ≤ 0.05 the difference between the Rmax values calculated for the reduced and relative measurement errors is not large. This allows us to use the developed formula for the dependence Rmax = Rmax (δ, d) at Rmax ≥ 0.8 for both relative and reduced measurement errors δ. The obtained result allows us using the reduced measurement error of a metrologically certified measuring instrument to obtain the maximum attainable correlation coefficient between the true values and the results of measuring a parameter in a given range of its change without measurements. As an example, we define the conditions for the non-destructive testing of steels under which one can use measuring of magnetic parameters with the installation certified based on the reduced measurement error.

Can the Planck Length Be Found Independent of Big G?

In this paper we show how it is possible to measure the Planck length through a series of different methods. One of these measurements is totally independent of big G, but moving from the theoretical realm to the empirical realm would require particle accelerators far more powerful than the ones that we have today. However, a Cavendish-style experiment can also be performed to find the Planck length with no knowledge of the value of big G. Furthermore, the Cavendish style set-up gives half of the relative measurement error in the Planck length compared to the measurement error in big G.

Relative measurement error analysis in the process of the Nakagami-m fading parameter estimation

An approach to the relative measurement error analysis in the process of the Nakagami-m fading signal moments estimation will be presented in this paper. Relative error expressions will be also derived for the cases when MRC (Maximal Ratio Combining) diversity technique is performed at the receiver. Capitalizing on them, results will be graphically presented and discussed to show the influence of various parameters, such as diversity order and fading severity on the relative measurement error bounds.

The Effect of Ultrapolish on a Transonic Axial Rotor

Back-to-back testing has been done using NASA fan rotor 67 in the Glenn Research Center W8 Axial Compressor Test Facility. The rotor was baseline tested with a normal industrial RMS surface finish of 0.5–0.6 μm (20–24 microinches) at 60, 80 and 100% of design speed. At design speed the tip relative Mach number was 1.38. The blades were then removed from the facility and ultrapolished to a surface finish of 0.125 μm (5 microinch) or less and retested. At 100% speed near the design point, the ultrapolished blades showed approximately 0.3–0.5% increase in adiabatic efficiency. The difference was greater near maximum flow. Due to increased relative measurement error at 60 and 80% speed, the performance difference between the normal and ultrapolished blades was indeterminate at these speeds.