Effective modulation of spin accumulation using a ferromagnetic/nonmagnetic bilayer spin channel

A lateral spin valve consisting of highly spin-polarized CoFeAl electrodes with a CoFeAl/Cu bilayer spin channel has been developed. Despite a large spin absorption into the CoFeAl capping channel layer, an efficient spin injection and detection using the CoFeAl electrodes enable us to observe a clear spin valve signal. We demonstrate that the nonlocal spin accumulation signal is significantly modulated depending on the relative angle of the magnetizations between the spin injector and absorber. The observed modulation phenomena is explained by the longitudinal and transverse spin absorption effects into the CoFeAl channel layer with the spin resistance model.

Optical Navigation-Related Factors Interfering With The Accuracy of Robot-Assisted Surgery

Objective To explore navigation-related factors interfering with accuracy of robot-assisted surgery. Methods We made a measurement model to test the accuracy of the TianJi Robot system when performing the stimulated screw placement procedure. The three-coordinate machine was used to measure the deviation between the actual position and the planned position. We designed corresponding experiments to explore the effects of different navigation-related factors on the screw placement accuracy. The deviations were measured at different distance (ranging from 1.2 m to 2.2 m) between the navigation optical stereo camera and the tracker and each distance was measured 50 times. The distance between the optical camera and the patient tracker was set at 1.4 m and the deviations were measured at different angles between the camera and the robot tracker, each angle was measured more than 25 times. Data was donated with mean and standard deviation. The line charts were employed to describe the changes of deviations over one clinical factor including distance and angle. Results Within the available scope of navigation optical system (1.2 m-2.2 m), the deviation increased with the distance (χ2=479.107, P<0.001). The robotic system accuracy was high and stable (mean deviation 0.332 mm ± 0.067 mm) when the relative angle between the optical camera and the tracker less than 40 degrees. Conclusions Accuracy of robot system was affected by the relative distance and angle between the optical camera and the tracker. When placing and adjusting the optical tracking devices, surgeons should set the relative distance between the optical camera and the patient tracker as 1.4 m- 1.5 m and the relative angle less than 40 degrees.

Combining Ergonomic Risk Assessment (RULA) with Inertial Motion Capture Technology in Dentistry—Using the Benefits from Two Worlds

Traditional ergonomic risk assessment tools such as the Rapid Upper Limb Assessment (RULA) are often not sensitive enough to evaluate well-optimized work routines. An implementation of kinematic data captured by inertial sensors is applied to compare two work routines in dentistry. The surgical dental treatment was performed in two different conditions, which were recorded by means of inertial sensors (Xsens MVN Link). For this purpose, 15 (12 males/3 females) oral and maxillofacial surgeons took part in the study. Data were post processed with costume written MATLAB® routines, including a full implementation of RULA (slightly adjusted to dentistry). For an in-depth comparison, five newly introduced levels of complexity of the RULA analysis were applied, i.e., from lowest complexity to highest: (1) RULA score, (2) relative RULA score distribution, (3) RULA steps score, (4) relative RULA steps score occurrence, and (5) relative angle distribution. With increasing complexity, the number of variables times (the number of resolvable units per variable) increased. In our example, only significant differences between the treatment concepts were observed at levels that are more complex: the relative RULA step score occurrence and the relative angle distribution (level 4 + 5). With the presented approach, an objective and detailed ergonomic analysis is possible. The data-driven approach adds significant additional context to the RULA score evaluation. The presented method captures data, evaluates the full task cycle, and allows different levels of analysis. These points are a clear benefit to a standard, manual assessment of one main body position during a working task.

A Torsion Relative Angle Measurement Method Based on Fiber-Loop Ring-Down with Intra-Cavity Amplification

Background: The fiber-loop ring-down spectroscopy technique has the benefits of optical fiber sensors and also has many unique advantages. Combined with various sensor structures, the FLRD system can achieve different physical, chemical, and biological sensors. Objective: To find a way to solve the problems of light fluctuation and low sensitivity, a high sensitivity and reliability torsion relative angle measurement system is necessary. Methods: The torsion relative angle measurement is achieved by using the fiber loop ring-down intra-cavity amplification. The sensitivity, correlation coefficient, and repeatability are analyzed with the experiment. Results: The sensitivity and correlation coefficient of the proposed system are 4.05 μs/° and 0.9996, respectively. The repeated experiments show that the standard deviation is 9.592×10-4. Conclusion: The proposed measurement method provides a way to solve the problems of light fluctuation and low sensitivity and has promising applications in the optically active solutions, fiber radial stress birefringence, and polarization state measurement of fiber lasers.

Analytical and Machine-LearningAnalysis of Hydraulic Fracture-Induced Natural Fracture Slip

Summary Stimulated reservoir volume (SRV) is a prime factor controlling well performance in unconventional shale plays. In general, SRV describes the extent of connected conductive fracture networks within the formation. Being a pre-existing weak interface, natural fractures (NFs) are the preferred failure paths. Therefore, the interaction of hydraulic fractures (HFs) and NFs is fundamental to fracture growth in a formation. Field observations of induced fracture systems have suggested complex failure zones occurring in the vicinity of HFs, which makes characterizing the SRV a significant challenge. Thus, this work uses a broad range of subsurface conditions to investigate the near-tip processes and to rank their influences on HF-NF interaction. In this study, a 2D analytical workflow is presented that delineates the potential slip zone (PSZ) induced by a HF. The explicit description of failure modes in the near-tip region explains possible mechanisms of fracture complexity observed in the field. The parametric analysis shows varying influences of HF-NF relative angle, stress state, net pressure, frictional coefficient, and HF length to the NF slip. This work analytically proves that an NF at a 30 ± 5° relative angle to an HF has the highest potential to be reactivated, which dominantly depends on the frictional coefficient of the interface. The spatial extension of the PSZ normal to the HF converges as the fracture propagates away and exhibits asymmetry depending on the relative angle. Then a machine-learning (ML) model [random forest (RF) regression] is built to replicate the physics-based model and statistically investigate parametric influences on NF slips. The ML model finds statistical significance of the predicting features in the order of relative angle between HF and NF, fracture gradient, frictional coefficient of the NF, overpressure index, stress differential, formation depth, and net pressure. The ML result is compared with sensitivity analysis and provides a new perspective on HF-NF interaction using statistical measures. The importance of formation depth on HF-NF interaction is stressed in both the physics-based and data-driven models, thus providing insight for field development of stacked resource plays. The proposed concept of PSZ can be used to measure and compare the intensity of HF-NF interactions at various geological settings.

A Parametric Study of Wave Energy Converter Layouts in Real Wave Models

Ocean wave energy is a broadly accessible renewable energy source; however, it is not fully developed. Further studies on wave energy converter (WEC) technologies are required in order to achieve more commercial developments. In this study, four CETO6 spherical WEC arrangements have been investigated, in which a fully submerged spherical converter is modelled. The numerical model is applied using linear potential theory, frequency-domain analysis, and irregular wave scenario. We investigate a parametric study of the distance influence between WECs and the effect of rotation regarding significant wave direction in each arrangement compared to the pre-defined layout. Moreover, we perform a numerical landscape analysis using a grid search technique to validate the best-found power output of the layout in real wave models of four locations on the southern Australian coast. The results specify the prominent role of the distance between WECs, along with the relative angle of the layout to dominant wave direction, in harnessing more power from the waves. Furthermore, it is observed that a rise in the number of WECs contributed to an increase in the optimum distance between converters. Consequently, the maximum exploited power from each buoy array has been found, indicating the optimum values of the distance between buoys in different real wave scenarios and the relative angle of the designed layout with respect to the dominant in-site wave direction.

Numerical Investigation on the Nonlinear Dynamics of Anisotropic Breathing Cracked Rotor Systems

The nonlinear breathing crack behaviors and anisotropy of the bearing are important sources of severe vibration of rotor systems. However, the rotor system considering both of these factors has not gained sufficient attention in the existing studies. In this paper, the nonlinear dynamics of such anisotropic breathing cracked rotor system is investigated based on three-dimensional finite element model (FEM). Firstly, the equations of motion of the rotor system are established in the rotating frame to facilitate the modeling of the breathing crack. The fixed-interface component mode synthesis (CMS) is used to reduce the system’s degrees of freedom (DOFs). Then, in the process of solving the equations by harmonic balance method (HBM) and Newton-Raphson method, an original method for fast calculating tangent stiffness matrix is proposed. Finally, the effects of the crack depth, the anisotropy of bearing and relative angle between bearings on the nonlinear dynamics of the system are studied. The results show that the breathing behavior will complicate the vibration and introduce additional transverse stiffness. The increase of crack depth will deteriorate the vibration. The anisotropy and relative angle of bearing will lead to the splitting and merging of the resonant peaks, respectively.