A Pre-Grasping Motion Planning Method Based on Improved Artificial Potential Field for Continuum Robots.

Secure and reliable active debris removal methods are crucial for maintaining the stability of the space environment. Continuum robots, with their hyper-redundant degrees of freedom, offer the ability to capture targets of varying sizes and shapes through whole-arm grasping, making them well-suited for active debris removal missions. This paper proposes a pre-grasping motion planning method for continuum robots based on an improved artificial potential field to restrict the movement area of the grasping target and prevent its escape during the pre-grasping phase. The analysis of the grasping workspace ensures that the target is within the workspace when starting the pre-grasping motion planning by dividing the continuum robot into delivery and grasping segments. An improved artificial potential field is proposed to guide the continuum robot in surrounding the target and creating a grasping area. Specifically, the improved artificial potential field consists of a spatial rotating potential field, an attractive potential field incorporating position and posture potential fields, and a repulsive potential field. The simulation results demonstrate the effectiveness of the proposed method. A comparison of motion planning results between methods that disregard and consider the posture potential field shows that the inclusion of the posture potential field improves the performance of pre-grasping motion planning for spatial targets, achieving a success rate of up to 97.8%.

The Modification Mechanism, Evaluation Method, and Construction Technology of Direct-to-Plant SBS Modifiers in Asphalt Mixture: A Review.

To further promote the development of research on direct-to-plant SBS-modified asphalt, this article analyzes the development of direct-to-plant SBS modifiers. Starting from the material composition and mechanism of action, common direct-to-plant SBS modifiers were analyzed and classified into four categories based on their mechanism of action, including the instant dissolution principle, intramolecular lubrication principle, non-granulation principle, and vulcanization principle. From the evaluation of the modification effect, the method of studying the performance of direct-to-plant SBS-modified asphalt is summarized, including fluorescence microscopy, AFM technology, and molecular dynamics simulation technology. From the perspective of practical application, the construction process of direct-to-plant SBS-modified asphalt was discussed, including the design stage, raw material preparation stage, mix design stage, and on-site construction stage. The results show that common direct-to-plant SBS modifiers are primarily SBS with a small particle size (less than 200 mesh) or specific model, supplemented by additives (EVA, naphthenic oil, sulfur, petroleum resin, etc.), which improve melting efficiency and lubricity or make it undergo vulcanization reaction, change the proportion of asphalt components, and improve stability. In the evaluation of the modification effect of direct-to-plant SBS-modified asphalt, the disparity of the direct-to-plant SBS modifier is determined by observing the particle residue after dry mixing. Macroscopic indexes of modified asphalt and modified asphalt mixture are used to determine the cross-linking effect of direct-to-plant SBS modifier and asphalt, and the modification mechanism and modification effect of wet SBS modifier are evaluated at the microscopic level. The development of direct-to-plant SBS-modified asphalt should combine the characteristics of direct-to-plant SBS modifiers and the attributes of field application, targeted research, and the development of high-performance direct-to-plant SBS modifiers and complete production technologies applicable to different regions, strengthen the improvement of modification effect evaluation, and form a complete theoretical system.

Integrated Navigation Algorithm Based on Multiple Fading Factors Kalman Filter.

An integrated navigation algorithm based on a multiple fading factors Kalman filter (MFKF) is proposed to solve the problems that the Kalman filtering (KF) algorithm easily brings about diffusion when the model becomes a mismatched or noisy, and the MFKF accuracy is reduced when the fading factor is overused. Based on the innovation covariance theory, the algorithm designs an improved basis for judging filtering anomalies and makes the timing of the introduction of the fading factor more reasonable by switching the filtering state. Different from the traditional basis of filter abnormality judgment, the improved judgment basis adopts a recursive way to continuously update the estimated value of the innovation covariance to improve the estimation accuracy of the innovation covariance, and an empirical reserve factor for the judgment basis is introduced to adapt to practical engineering applications. By establishing an inertial navigation system (INS)/global navigation satellite system (GNSS) integrated navigation model, the results show that the average positioning accuracy of the proposed algorithm is improved by 26.52% and 7.48%, respectively, compared with the KF and MFKF, and shows better robustness and self-adaptability.

Non-contact Breathing Rate Detection Based on Time of Flight Sensor.

There are a growing number of methods to detect a person's breathing rate, but most techniques still either require contact with body skin or are usually uncomfortable to wear, too expensive and unfriendly for daily monitoring. The massive adoption of smartphones in recent years has created many opportunities to improve daily health monitoring. In this work, we demonstrated that off-the-shelf ToF lens on smartphones can capture a person's breathing rate while still. In addition, we proposed a method for extracting breathing rate from ToF signal and compared it with actual breathing rate obtained from temperature sensor. We evaluated the breathing rate accuracy of 6 people at rest, with a mean absolute error of 0.009Hz when considering different mean breathing rate conditions. Moreover, the mean absolute error percentage is 3.56% and the root mean squared percentage error is 6.64%, which is smaller than other methods of non-contact breathing rate detection in recent works.

High-Fluidization, Early Strength Cement Grouting Material Enhanced by Nano-SiO2: Formula and Mechanisms.

Cement grouting material is one of the most important materials in civil construction at present, for seepage prevention, rapid repair, and reinforcement. To achieve the ever-increasing functional requirements of civil infrastructures, cement grouting materials must have the specific performance of high fluidization, early strength, and low shrinkage. In recent years, nanomaterials have been widely used to improve the engineering performance of cement grouting materials. However, the mechanisms of nanomaterials in grouting materials are not clear. Hence, a high-fluidization, early strength cement grouting material, enhanced by nano-SiO2, is developed via the orthogonal experimental method in this study. The mechanisms of nano-SiO2 on the microstructure and hydration products of the HCGA, in the case of different curing ages and nano-SiO2 contents, are analyzed through scanning electron microscopy tests, X-ray diffraction tests, differential scanning calorimetry tests, and Fourier transform infrared spectroscopy tests.

On the structure of α-BiFeO3.

Polycrystalline and monocrystalline α-BiFeO3 crystals have been synthesized by solid state reaction and flux growth method, respectively. X-ray, neutron, and electron diffraction techniques are used to study the crystallographic and magnetic structure of α-BiFeO3. The present data show that α-BiFeO3 crystallizes in space group P1 with a = 0.563 17(1) nm, b = 0.563 84(1) nm, c = 0.563 70(1) nm, α = 59.33(1)°, ß = 59.35(1)°, γ = 59.38(1)°, and the magnetic structure of α-BiFeO3 can be described by space group P1 with magnetic modulation vector in reciprocal space q = 0.0045a* - 0.0045b*, which is the magnetic structure model proposed by I. Sosnowska (1) applied to the new P1 crystal symmetry of α-BiFeO3.

Size- and shape-controlled synthesis of monodisperse vanadium dioxide nanocrystals.

Highly monodisperse VO2 nanocrystals with finely defined sizes and shapes were synthesized for the first time by thermolysis of single source vanadium precursor in high boiling point solvents of oleic acid (OA), oleylamine (OM), and octadence (ODE). The resulting VO2 nanocrystals were characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-Ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). It was revealed that the low valence vanadium oxide of VO2 nanocrystals was successfully synthesized via this approach, and the obtained VO2 nanocrystals displayed uniform sizes and narrow size distribution with size variation in range of approximately 4-20 nm under various synthetic conditions. The previously unknown cubic, polyhedral shaped VO2 nanocrystals were achieved as well through modulating the preparative conditions. The solvent composition and precursor concentration are found to have profound effects on the sizes and shapes of the final VO2 nanocrystals. It is expected that the obtained VO2 nanocrystals with finely controlled sizes and shapes may be valuable candidates for studying and realizing the new size- and shape- dependent optical and electrical properties of VO2 materials in the nanoscale realm, and the novel synthetic method is potentially useful for the controlled synthesis of high quality doped VO2 and other vanadium oxides nanocrystals.