Soft joint shape measurement device based on FBG with a simple demodulating system.

Soft joint shape measurement is challenging because, in most cases, it relies solely on internal sensors. Existing shape estimation methods commonly take measurements at discrete points and utilize curve-fitting schemes, which are inefficient for complex joint shapes that require continuous measurements. Therefore joint shape measurement sensors rely on the fiber Bragg grating (FBG) due to its sensitivity, immunity to electromagnetic interference, and flexibility. Nevertheless, FBG demodulation is still an open research case. Hence, we propose a shape measurement device appropriate for FBG-based continuous measurements that employs a sensor with only three FBGs thrusting inside the soft joint to measure its 3D shape. Moreover, we develop a simple demodulating system exploiting the FBG's filter overlapping properties and design a calibrating process for FBG signals. Soft joint shape measurement experiments highlight our method's effectiveness, providing a relative error within 0.7%. Further tests involving continuum robot measurement reveal that the achieved precision is of the same level as a motion-capturing system.

Evaluation of the communication quality of free-space laser communication based on the power-in-the-bucket method.

Atmospheric turbulence seriously affects the quality of free-space laser communication. The Strehl ratio (SR) is used to evaluate the effect of atmospheric turbulence on the receiving energy of free-space laser communication systems. However, the SR method does not consider the area of the laser-receiving end face. In this study, the power-in-the-bucket (PIB) method is demonstrated to accurately evaluate the effect of turbulence on the receiving energy. A theoretical equation is first obtained to calculate PIB. Simulated and experimental validations are then performed to verify the effectiveness of the theoretical equation. This work may provide effective guidance for the design and evaluation of free-space laser communication systems.

JamTac: A Tactile Jamming Gripper for Searching and Grasping in Low-Visibility Environments.

Humans can feel and grasp efficiently in the dark through tactile feedback, whereas it is still a challenging task for robots. In this research, we create a novel soft gripper named JamTac, which has high-resolution tactile perception, a large detection surface, and integrated sensing-grasping capability that can search and grasp in low-visibility environments. The gripper combines granular jamming and visuotactile perception technologies. Using the principle of refractive index matching, a refraction-free liquid-particle rationing scheme is developed, which makes the gripper itself to be an excellent tactile sensor without breaking its original grasping capability. We simultaneously acquire color and depth information inside the gripper, making it possible to sense the shape, texture, hardness, and contact force with high resolution. Experimental results demonstrate that JamTac can be a promising tool to search and grasp in situations when vision is not available.

Application of high precision wavelength calibration method for plasmas rotation measurement based on Fabry-Pérot etalon on experimental advanced superconducting tokamak.

Analyzing the radiation spectra of impurity ions is a widely applied diagnostic scheme for plasma ion temperature and rotation measurements on tokamaks. High precision wavelength calibration is a prerequisite for the accurate measurement of plasma parameters, especially for plasma rotation. Furthermore, the sparseness or absence of the standard spectral lines brings calibration challenges due to the narrow wavelength range. A precise wavelength calibration method is demonstrated in which the comb-like spectra generated by the Fabry-Pérot etalon can lock a series of fixed peaks as reference points in a wide wavelength range. The equal frequency intervals of the comb-like spectra are further corrected using several characteristic neon lines of known wavelengths. The experimental results indicate that the wavelength accuracy obtained by this calibration method is less than 0.005 nm, which corresponds to a rotation speed of 2.3 km/s in the toroidal direction for the beam emission spectroscopy spectrometer installed on the experimental advanced superconducting tokamak. Taking the O V(650.024 nm, n = 4 → 3) line as an example, the maximum difference in the oxygen ion rotation velocity is 3.8 km/s for the absolute rotation of ∼25 km/s, when compared with the calibration results of a standard lamp.

Performance analysis of an adaptive optics system for free-space optics communication through atmospheric turbulence.

The performance of free-space optics communication (FSOC) is greatly degraded by atmospheric turbulence. Adaptive optics (AO) is an effective method for attenuating the influence. In this paper, the influence of the spatial and temporal characteristics of turbulence on the performance of AO in a FSOC system is investigated. Based on the Greenwood frequency (GF) and the ratio of receiver aperture diameter to atmospheric coherent length (D/r 0 ), the relationship between FSOC performance (CE) and AO parameters (corrected Zernike modes number and bandwidth) is derived for the first time. Then, simulations and experiments are conducted to analyze the influence of AO parameters on FSOC performance under different GF and D/r 0 . The simulation and experimental results show that, for common turbulence conditions, the number of corrected Zernike modes can be fixed at 35 and the bandwidth of the AO system should be larger than the GF. Measurements of the bit error rate (BER) for moderate turbulence conditions (D/r 0 = 10, f G = 60 Hz) show that when the bandwidth is two times that of GF, the average BER is decreased by two orders of magnitude compared with f G /f 3dB = 1. These results and conclusions can provide important guidance in the design of an AO system for FSOC.

[Effectiveness of low molecular weight heparin for prevention of deep vein thrombosis after total hip arthroplasty].

OBJECTIVE: To investigate the pathogenesis of deep vein thrombosis (DVT) after total hip arthroplasty (THA) and the preventive effectiveness of low molecular weight heparin (LMWH). METHODS: The occurrence condition of DVT in 90 cases undergoing THA treated with LMWH between February 2003 and March 2004 was retrospectively analyzed. Among 90 cases, 39 were treated with LMWH at a dose of 5000 U/day (high dose group) and 51 at a dose of 2500 U/day (low dose group). Another 90 cases undergoing THA without LMWH treating between February 2002 and February 2003 were used as control group. There was no significant difference in gender, age, illness cause, course of disease, or the type of prosthesis among 3 groups (P > 0.05). RESULTS: DVT occurred in 19 cases (21.1%) of control group, in 2 cases (5.1%) of high dose group, and in 5 cases (9.8%) of low dose group, showing significant differences between two treated groups and control group (P < 0.05), but no significant difference between two treated groups (P > 0.05). There was no significant difference in gender, age (> 65 years and < or = 65 years), pathogen (trauma and bone disease) of each group, as well as of the same type patients within 3 groups (P > 0.05). The DVT incidence rate in the patients with bone cement artificial joint was significantly higher than that in the patients with non-bone cement artificial joint (P < 0.05), but there was no significant difference in the same type patients within 3 groups (P > 0.05). The postoperative blood loss in high dose group, low dose group, and control group was (463.5 +/- 234.2), (342.4 +/- 231.6), and (288.2 +/- 141.6) mL; showing no significant difference between the high and low dose groups, between low dose and control groups (P > 0.05), while showing significant difference between high dose and control groups (P < 0.05). CONCLUSION: The DVT incidence rate in THA patients with bone cement artificial joint is high; LMWH can reduce the DVT incidence rate and has good safety.