Efficient 3D scanning measurement system based on asymmetric trinocular vision and a multi-line laser.

The laser scanning measurement system has a pivotal role in precision measurement thanks to the non-contacting and low-cost advantages, but traditional methods and systems are inadequate in terms of accuracy, efficiency, and adaptability. In this study, an efficient 3D scanning measurement system based on asymmetric trinocular vision and a multi-line laser is developed to improve the measurement performance. The system design, working principle, and 3D reconstruction method are explored, as well as the innovation of the developed system. Furthermore, an efficient multi-line laser fringes indexing method is presented based on K-means ++ clustering and hierarchical processing to improve processing speed with guaranteed accuracy, which is the key point of the 3D reconstruction method. Various experiments are conducted to verify the capability of the developed system, and the results show that the developed system fulfills measurement needs in adaptability, accuracy, effectiveness, and robustness. The developed system achieves better results than commercial probes for complex measurement conditions, and measurement precision can be achieved to within 18 µm.

Accuracy improvement of multi-view 3D laser scanning measurements based on point cloud error correction and global calibration optimization.

Multi-camera laser scanning measurement is emerging as a pivotal element in three-dimensional (3D) optical measurements. It reduces occlusion and enables the gathering of more 3D data. However, it also increases the difficulty of system algorithms in obtaining high measurement accuracy. To improve the measurement accuracy, there is an urgent need to address global calibration and error correction issues caused by the employment of multi-view systems. An accuracy improvement method for multi-view 3D laser scanning measurements based on point cloud error correction and global calibration optimization is then proposed. First, a planar asymmetric circular grid target is designed to calibrate the cameras, laser planes, and initial global transformation matrices of the multi-view 3D laser scanning probe simultaneously. The influence of the position of the laser plane on the measurement error is analyzed and what we believe to be novel mathematical error influencing factors are then modelled for point accuracy. Furthermore, a believed to be novel error model based on the backpropagation (BP) neural network is established for the regression analysis of the mathematical error influencing factors and measurement deviations for each point based on the standard sphere plate measurement. The final measurement is optimized by the correction of point cloud for each camera of the multi-view system and the global calibration optimization based on the error model. The proposed method is reliable and easy to implement, since it only requires a standard sphere plate and a planar target. Several experiments show that the method can effectively improve the measurement accuracy of multi-view 3D laser scanning probe through point cloud error correction and calibration optimization.

Three-Dimensional Printing and Recycling of Multifunctional Composite Material Based on Commercial Epoxy Resin and Graphene Nanoplatelet.

3D printing of commercial thermosetting epoxy resin is of great significance for the rapid and low-cost construction of high-strength objects with complex structures. Meanwhile, recycling these commercial epoxy resins is essential for environmental protection and sustainable development. This paper reports direct ink writing 3D printing of a multifunctional composite material based on commercial bisphenol A epoxy resin and a 3D printing compatible technique to recycle the printed composite material. Graphene nanoplatelet is designed as an efficient functional thixotropic additive that turns the liquid epoxy resin prepolymer shear-thinning and suitable for direct ink printing. Composite materials with high resolution and high mechanical strength are printed with epoxy resin/graphene nanoplatelet inks, and they also show high thermal and electrical conductivity and fast thermo-induced shape memory response. The printed objects can be recycled by comminuting them into micropowders, which are then used as a thixotropic agent to prepare recycled DIW ink. The physical properties of the materials printed with recycled inks maintain unchanged for successive four recycling cycles. The graphene nanoplatelets at the surface of recycled comminuted powder are found to modulate the surface energy of the powder, thus making the powder able to serve as a thixotropic agent for the recycled inks. The method here provides a new solution to process commercial epoxy resin and opens a new direction to the more sustainable use of thermosetting plastics.

Correction of the air refractive index using a two-color method for absolute distance measurement without a dead zone.

In the fields of satellite formation, large-scale manufacturing, and ultra-precision machining, high-precision ranging based on the femtosecond laser is one of the necessary technologies. However, the fluctuations of the air refractive index and the limited tuning range of repetition rate restrict the measurement precision and range. Using only one femtosecond comb that corrects the air refractive index simultaneously, a method for ranging without the dead zone of measurement is described. A delay optical path is established in the ranging system to eliminate the dead zone of measurement by a comb. Meanwhile, in order to ensure the consistency of the pulse sequence between the fundamental frequency beam and the second-harmonic beam after the delay optical path, the second-harmonic beam generates on the delay optical path after the fundamental harmonic passes the long fiber. A two-color method is used to correct the effect of the air refractive index. The experimental result demonstrates the measurement precision of 7.2 µm at ∼0.8m with correction of the air refractive index, and the precision of measurement is 8.4 µm at ∼2.2m. Finally, the maximum deviation between our system and the reference standard is 5.0 µm.

3D Printing of a Polydimethylsiloxane/Polytetrafluoroethylene Composite Elastomer and its Application in a Triboelectric Nanogenerator.

Silicone rubber elastomers are broadly used in various fields, where the three-dimensional (3D) printing of silicone rubber elastomers is important for the free construction of complex structures. Herein, a series of polydimethylsiloxane/polytetrafluoroethylene composite inks for direct-ink-writing 3D printing are developed. The inks are prepared by directly mixing a silicone rubber liquid precursor with polytetrafluoroethylene micropowder. The polytetrafluoroethylene micropowder serves as a thixotropic agent to regulate the rheological properties of the polydimethylsiloxane precursor to fulfill the requirement of 3D printing and endow the composite material with high electron affinity. The printed polydimethylsiloxane/polytetrafluoroethylene composite elastomer exhibits excellent elasticity and cyclic stability. A high-performance triboelectric nanogenerator is constructed with the 3D-printed polydimethylsiloxane/polytetrafluoroethylene composite as the triboelectric layer and elastic structure. This work establishes a new method of 3D printing polydimethylsiloxane-based elastomers and thus provides a new technique for constructing complex structures in flexible devices.

Superacid-doped polyaniline as a soluble polymeric active electrolyte for supercapacitors.

Using polyaniline as a soluble electrochemically active additive in an electrolyte has the advantages of high pseudocapacitance and good cycle stability of polyaniline, however, the challenge is how to make polyaniline soluble in the electrolyte. In this study, we prepare a solution of polyaniline in N-methylpyrrolidone by protonating polyaniline with trifluoromethyl sulfonic acid. Spectroscopic and electrochemical results indicate that the weak binding interaction, between trifloromethyl sulfonate ions and protonated polyaniline chains, increases the solubility of trifloromethyl sulfonic acid doped polyaniline. An active electrolyte system composed of 15 mg mL-1 polyaniline and 0.4 M trifluoromethyl sulfonic acid in N-methylpyrrolidone is developed. With the active electrolyte and reduced graphene oxide as the electrodes, the fabricated supercapacitor shows a higher specific capacitance than the corresponding electric double-layer supercapacitors. Because the volume change and hydrolyzation of polyaniline, which are the main causes of the performance degradation in polyaniline-based supercapacitors, are avoided, the present supercapacitor exhibits an excellent cycle stability of 100% capacitance retention after 10 000 cycles. This work demonstrates the possibility of directly using a conductive polymer as an active electrolyte in supercapacitors with high cycle stability.

Facile synthesis of multi-functional elastic polyaniline/polyvinyl alcohol composite gels by a solution assembly method.

Polyaniline gels with a three-dimensional network structure are attractive for their broad application prospects in flexible and stretchable electric devices. In this paper, we develop a facile solution assembly method to prepare an elastic polyaniline/poly(vinyl alcohol) composite organogel and a hydrogel. The polyaniline and poly(vinyl alcohol) chains gelate from the homogeneous mixed solution in N-methyl-2-pyrrolidone via crystallization of poly(vinyl alcohol), producing a uniform organogel with hydrogen bonds between two polymers, and the organogel can be further converted into a hydrogel by solvent exchange. The composite gels exhibit excellent mechanical properties, which make them one of the best materials for additive manufacture, such as molding and 3D printing. This study develops an efficient method to fabricate polyaniline gels with good processability and multifunctions.

Comparison of cancer detection between 18- and 12-core prostate biopsy in Asian patients with prostate-specific antigen levels of 4-20 ng/mL.

BACKGROUND: Although prostate biopsy is an accepted option for cancer detection, there is little data regarding the clinical outcome of 18-core transrectal ultrasound (TRUS)-guided biopsy. This retrospective study compared cancer detection rates and biopsy complications between 12- and 18-core TRUS biopsy in Asian patients with prostate-specific antigen (PSA) levels between 4.0 and 20.0 ng/mL. METHODS: In total, 1120 consecutive patients with PSA levels between 4.0 and 20.0 ng/mL were divided into the 12-core (552 patients) and 18-core TRUS biopsy (568 patients) groups. The clinical outcomes of the 12- and 18-core TRUS-biopsy groups were compared. Clinical outcomes were evaluated by comparing the prostate cancer detection rates and post-biopsy complication rates. RESULTS: There were no significant group differences in the PSA levels, but the mean age was significantly older in the 12-core biopsy group than in the 18-core biopsy group (mean age, 67.0 vs. 64.0 years, respectively; p = 0.001). The abnormal digital rectal examination rate was higher in the 12-core biopsy group than in the 18-core biopsy group (39.9% vs. 24.5%, respectively; p < 0.001). The prostate cancer detection rate was significantly higher in the 18-core group than in the 12-core group [adjusted odds ratio: 2.75, 95% confidence interval = 2.04-3.01; p < 0.001], especially in patients with age ≥ 50 years, PSA < 10 and cancer clinical stage cT1. (p < 0.001). Moreover, in patients with prostate volumes >30 mL or PSA densities <0.2, the prostate cancer detection rate was significantly higher in the 18-core group than in the 12-core group. There were no differences in the complication rates (e.g., urinary retention, hematuria, urinary tract infection, and urosepsis). CONCLUSION: In Asian patients with serum PSA levels between 4.0 and 20.0 ng/mL, 18-core biopsy was associated with superior clinical outcomes to those of 12-core biopsy for detecting prostate cancer.