A novel instrumented outsole for real-time foot kinematics measurement: validation across different speeds and simulated foot landing in Cerebral Palsy gait

Neuromuscular disorders in Cerebral Palsy (CP) patients lead to foot deformities and affect foot biomechanics leading to compromised gait. The objective of the present work is to develop a wearable instrumentation to measure foot kinematics such as foot-to-ground angle in three-dimensional planes and to measure the foot clearance i.e., toe and heel clearances. A template-based outsole was developed that incorporated an optical distance sensor located anatomically on the outsole and the magnetometer to measure the foot kinematics. The developed system was validated against the reference marker-based motion capture system. The data from eight able-bodied participants were acquired simultaneously from both the systems at three different walking speeds. A CoP based feedback was presented to the participants to shift the sagittal CoP anteriorly, posteriorly and normal to simulate the walking pattern of CP patients with three different foot landing strategies. Pearson’s correlation coefficient of more than or equal to 0.62, root mean square error of less than or equal to 7.81 degrees and limit of agreement of more than or equal to 95% is found. The measurement accuracy reported with outsole while participants simulated CP gait shows the potential of present work in real-time foot kinematics detection in CP patients.

Phase Stability under Thermal Drifts in Photodiode-Conditioning Transimpedance Amplifiers for Distance Metrology

Transimpedance amplifiers (TIA) are widely used for front-end signal conditioning in many optical distance measuring applications in which high accuracy is often required. Small effects due to the real characteristics of the components and the parasitic elements in the circuit board may cause the error to rise to unacceptable levels. In this work we study these effects on the TIA delay time error and deduce analytic expressions, taking into account the trade-off between the uncertainties caused by the delay time instability and by the signal-to-noise ratio. A specific continuous-wave phase-shift case study is shown to illustrate the analysis, and further compared with real measurements. General strategies and conclusions, useful for designers of this kind of system, are extracted too. The study and results show that the delay time thermal stability is a key determinant factor in the measured distance accuracy and, without an adequate design, moderate temperature variations of the TIA can cause extremely high measurement errors.

Comparative study of accuracy of differential global positioning system (DGPS) and total station instruments

Total Station and Global Positioning System (GPS) are two instruments used to fix position on the earth. The total station employs electro-optical distance meter method, emitting laser beams to a target and detecting light reflected off it by measuring the deviation of the wavelength of the reflected light. Global Positioning System (GPS) is a space-based satellite for rapid position determination, its’ receiver calculates its position by precisely turning the signal sent by GPS satellite high above the earth. The study aims at the assessment of the two instruments: GPS and Total Station. To achieve this aim, two surveys were performed on the same parcel of land using the two instruments. In the first part of the survey, a closed-loop traverse was performed around a chosen parcel of land using a calibrated total station. The station determined only coordinates of points from where bearings and distances were extracted. Thereafter, DGPS equipment was then used to perform a similar survey as the total station. In this case, visible satellites were used to determine the coordinates of all the stations. The results of the two methods present the distances, bearings, and coordinates. The difference between each of the results was also analyzed. Thus the maximum average difference in distance of 5mm occurred throughout the chainage and maximum differences in the coordinate of 12mm Easting and 9mm Northing were found where there are tree covers. However, the study shows that even though the two instruments are good tools for positioning, each exhibited it’s own accuracy, efficiency, advantages and disadvantage.

Toward Cloud Tomography from Space Using MISR and MODIS: Locating the “Veiled Core” in Opaque Convective Clouds

For passive satellite imagers, current retrievals of cloud optical thickness and effective particle size fail for convective clouds with 3D morphology. Indeed, being based on 1D radiative transfer (RT) theory, they work well only for horizontally homogeneous clouds. A promising approach for treating clouds as fully 3D objects is cloud tomography, which has been demonstrated for airborne observations. However, more efficient forward 3D RT solvers are required for cloud tomography from space. Here, we present a path forward by acknowledging that optically thick clouds have “veiled cores” (VCs). Sunlight scattered into and out of this deep region does not contribute significant information about the inner structure of the cloud to the spatially detailed imagery. We investigate the VC location for the MISR and MODIS imagers. While MISR provides multiangle imagery in the visible and near-infrared (IR), MODIS includes channels in the shortwave IR, albeit at a single view angle. This combination will enable future 3D retrievals to disentangle the cloud’s effective particle size and extinction fields. We find that, in practice, the VC is located at an optical distance of ~5, starting from the cloud boundary along the line of sight. For MODIS’s absorbing wavelengths the VC covers a larger volume, starting at smaller optical distances. This concept will not only lead to a reduction in the number of unknowns for the tomographic reconstruction but also significantly increase the speed and efficiency of the 3D RT solver at the heart of the algorithm by applying, say, the photon diffusion approximation inside the VC.

The integrated geodetic monit oring system of open pit slopes in hard rock massifs

The article describes an experience in organizing the integrated geomechanical monitoring in high-strength hard rock massifs using the longstanding GPS and optical distance measurements in the Zhelezny open pit, Kovdorsky GOK JSC, as well as measurements with the IBIS FM interferometric radar. The application of the integrated monitoring system in the Zhelezny open pit has allowed accumulation of significant statistical material, which made it possible to identify the patterns of the rock mass deformation development, determine the limiting parameters and develop several regulatory documents for observing and processing the measurement results of the benches and open pit walls displacements.

Water Temperature and Salinity Measurement Using Frequency Comb

Water temperature and salinity are key parameters in many fields such as industry, forestry and agriculture. In this paper, we, theoretically and experimentally, demonstrate a method which is capable of water temperature and salinity measurement based on a laser frequency comb at 518 nm. We have developed a simple Michelson interferometer system. By scanning a mirror on a precision displacement platform, a pair of cross-correlation patterns can be obtained. The real-time optical distance information from these cross-correlation patterns can be used to calculate the optical distance difference changes. Temperature and salinity can be measured via these changes, aided by the empirical formulas. Compared with the reference values, our results show the differences of below 0.12 °C for temperature measurements, and 0.06 ‰ for salinity measurements. The obtained results indicate that our method can offer a powerful scheme for future temperature and salinity measurement.