Search

The lack of tissue traction and instrument dexterity to allow for adequate visualization and effective dissection were the main issues in performing endoscopic submucosal dissection (ESD). Robot-assisted systems may provide advantages. In this study we developed a novel transendoscopic telerobotic system and evaluated its performance in ESD. A miniature dual-arm robotic endoscopic assistant for minimally invasive surgery (DREAMS) was developed. The DREAMS system contained the current smallest robotic ESD instruments and was compatible with the commercially available dual-channel endoscope. After the system was established, a prospective randomized controlled study was conducted to validate the performance of the DREAMS-assisted ESD in terms of efficacy, safety, and workload by comparing it with the conventional technique. Two robotic instruments can achieve safe collaboration and provide sufficient visualization and efficient dissection during ESD. Forty ESDs in the stomach and esophagus of 8 pigs were completed by DREAMS-assisted ESD or conventional ESD. Submucosal dissection time was comparable between the 2 techniques, but DREAMS-assisted ESD demonstrated a significantly lower muscular injury rate (15% vs 50%, P =.018) and workload scores (22.30 vs 32.45, P <.001). In the subgroup analysis of esophageal ESD, DREAMS-assisted ESD showed significantly improved submucosal dissection time (6.45 vs 16.37 minutes, P =.002), muscular injury rate (25% vs 87.5%, P =.041), and workload (21.13 vs 40.63, P =.001). We developed a novel transendoscopic telerobotic system, named DREAMS. The safety profile and technical feasibility of ESD were significantly improved with the assistance of the DREAMS system, especially in the narrower esophageal lumen. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper has proposed a novel fiber Bragg grating (FBG)-based hybrid displacement and force sensor with a compact structure and excellent resolution by using the transverse property of a tightly suspended and slightly bent optical fiber. The optical fiber, embedded with an FBG element, has been suspended with its ends fixed on the sensor frame and implemented with a pre-tension force by the displacement loading along its vertical direction to form a bent shape. A conversion mechanism has been designed to convert the displacement and force inputs into the transverse movement of different points along the suspended fiber. Experimental results show that the displacement sensitivity and force sensitivity are −219.69 pm/mm within the range of 0–2.5 mm and −345.2 pm/N with a high calculated resolution of 2.9 mN, respectively. Results from both the displacement and force experiments have illustrated a close agreement with values from commercial sensors. [ABSTRACT FROM AUTHOR]

A broadband photonic crystal (PhC) waveguide crossing is proposed with low crosstalk. On the basis of the structure, two 1 × 2 PhC λ-routers are constructed by exploiting several PhC point-defect micro-cavities. By means of the interference coupling between the point-defect modes in micro-cavities, the incidence light with the resonant wavelength can be routed to the designed output port in the router. To achieve the high routing efficiency with narrow pass-band width, the micro-cavity structure is elaborately engineered to satisfy the condition of the quality factor ratio, which consists of these rods with the gradual radii. Their performances are demonstrated by the numerical results calculated by the finite difference time domain (FDTD) and the plane wave expansion (PWE) methods. Furthermore, the analysis of the 4 × 4 λ -router configuration, obtained by assembling these basic wavelength routing elements, is reported to highlight its performances with a theoretical maximum crosstalk between the ports equal to −27.23 dB. [ABSTRACT FROM AUTHOR]

Snake-like flexible manipulators are widely used in minimally invasive surgery (MIS), which require adequate dexterity in confined workspace. Typically, the design mechanisms of these manipulators include tendon-driven mechanism and concentric tube mechanism. Though, the workspace and dexterity of these designs are limited due to the lack of control in either the length of the bending section or the curvature of the bending section at the distal end. In this paper, we present a novel constrained wire-driven flexible mechanism (CWFM), in which both the length and the curvature of the bending section are controllable. The idea is to employ an active constraint to control the length of the bending section and use the wires to control the curvature of the bending section. Compared to the existing designs based on wire-driven flexible mechanism (WFM), CWFM has expanded workspace and enhanced dexterity while its size is not sacrificed. Additional benefits include much reduced sweeping area and controllable stiffness. Based on the computer simulation, on average, CWFM with the same size as WFM can improve the dexterity by 4.69 times and reduce the sweeping area to 20.5%. [ABSTRACT FROM AUTHOR]

Abstract: We present a photonic crystal (PC) three-port channel drop filter (CDF) with flat-top response and high quality factor value of 8836.7, and it can be used in the dense wavelength division multiplexing (DWDM) system. The CDF is engineered based on the three-port system with the wavelength-selective reflection feedback, where both micro-cavities are the synthesized coupled-resonators. In this case, the conditions to achieve complete power transfer are same to that of the corresponding three-port system while both micro-cavities are the single-mode resonators. As two micro-cavities are single point-defect resonators or synthesized coupled-resonators respectively, it is confirmed that these CDFs exhibit different response characteristics by the simulation results calculated by using two dimensional finite-difference time-domain (2D-FDTD) method, and these filters will find applications in future wavelength division multiplexing (WDM) optical communication systems. [Copyright &y& Elsevier]

Abstract: As an important component of scanning near-field optical microscope (SNOM), optical fibre nanoprobe has been applied to many fields extensively. A melt-stretched etching method is proposed to produce optical fibre nanoprobe with low cost. Firstly, optical fibre tip with micrometer-sized diameter is created by the melt-stretched measure. Next, it is dipped into hydrofluoric acid (HF), and a fine optical fibre nanoprobe will be made after a short-time etching. Owing to the taper structure of tip, it can be etched again in acid if a nanoprobe is not constructed when the first etching is completed. In addition, optical fibre nanoprobe is applied to spectral investigation, and the fluorescence spectroscopy of rhodamine B (Rh B) solution is collected by an optical investigation system with a bifurcated fibre. [Copyright &y& Elsevier]

Abstract: A novel three-port channel add/drop filter consisting of two waveguides and two cavities is proposed. One is used for a resonant tunneling-based channel add/drop operation from the bus waveguide to the add/drop waveguide, while the other is used to realize the wavelength-selective reflection feedback in the bus waveguide. By means of coupled mode theory in time, the conditions to achieve 100% add efficiency are derived thoroughly. Based on these theoretical analysis, the channel add filter and some other multi-channel filters are designed in two-dimensional photonic crystals (2D PCs) with square lattice of dielectric rods in air. The numerical results by using the finite-difference time-domain (FDTD) method demonstrate almost complete channel add/drop tunneling at resonance via the three-port systems. [Copyright &y& Elsevier]

This work presents a novel soft actuator with a 3D-printed elastic body based on a fused-deposition-modeling technique and with tendon actuation based on flexible shafts, which allow push, pull, and twist torque transmissions. The combination of the soft body and flexible shaft furnishes an easy-making, modular and functional unit that possesses softness and enables three degrees of freedom. We derive the kinematics and statics of the actuator based on the assumption of piecewise constant curvature, and identify the parameters experimentally. To understand the performance of the soft actuator in different design and fabrication settings, extensive experiments are performed to compare different shapes of cross sections, infill densities, infill patterns, dentation structures and moment arms in terms of generating forces under the same pulling forces. In addition, experimental validations are performed to characterize other properties such as workspace, hysteresis, pushing force, transmitted torque, and tip force under both bending and twisting. Finally, three potential applications, i.e., a soft robotic hand, a multisegment continuum robot, and a miniaturized drilling device, are prototyped and presented experimentally where the flexibility endowed by the shafts is demonstrated and highlighted. The scalability and modularity are also showcased in the three applications. [ABSTRACT FROM AUTHOR]

This paper develops a novel shared control scheme for online-switching tele-operated and autonomous system with time-varying delays. Type-2 Takagi–Sugeno (T–S) fuzzy model is used to describe the dynamics of master and slave robots in this system. A novel non-singular fast terminal siding mode (NFTSM)-based algorithm combined with an extended wave-based time domain passivity approach (TDPA) is presented to enhance the master–slave motion synchronization in the tele-operated mode and reference-slave motion synchronization in the autonomous mode, while simultaneously ensuring the stability of the overall system in the presence of arbitrary time delays. In addition, based on the Type-2 Fuzzy model, a new torque observer is designed to estimate the external torques and then the torque tracking method is employed in the control laws to let the slave apply the designated force to further improve the operator’s force perception for the environment. The stability of the closed-loop system is proven using the Lyapunov–Krasovskii functions. Finally, experiments using two haptic devices prove the superiority of the proposed strategy. [ABSTRACT FROM AUTHOR]

Robot manipulators are increasingly used in minimally invasive surgery (MIS). They are required to have small size, wide workspace, adequate dexterity and payload ability when operating in confined surgical cavity. Snake-like flexible manipulators are well suited to these applications. However, conventional fully actuated snake-like flexible manipulators are difficult to miniaturize and even after miniaturization the payload is very limited. The alternative is to use underactuated snake-like flexible manipulators. Three prevailing designs are tendon-driven continuum manipulators (TCM), tendon-driven serpentine manipulators (TSM) and concentric tube manipulators (CTM). In this paper, the three designs are compared at the mechanism level from the kinematics point of view. The workspace and distal end dexterity are compared for TCM, TSM and CTM with one, two and three sections, respectively. Other aspects of these designs are also discussed, including sweeping motion, scaling, force sensing, stiffness control, etc. From the results, the tendon-driven designs and concentric tube design complement each other in terms of their workspace, which is influenced by the number of sections as well as the length distribution among sections. The tendon-driven designs entail better distal end dexterity while generate larger sweeping motion in positions close to the shaft. [ABSTRACT FROM AUTHOR]

To radically eliminate the influence of coupling torque caused by gyroscopic effects on system stability and precision and to improve the high precision performance of the low speed gimbal servo system in a double gimbal control moment gyro (DGCMG), this paper proposes a novel composite controller design method combining state feedback linearization and adaptive sliding mode control method. The precision problem caused by residual coupling and nonlinear friction have been successfully solved by introducing an adaptive sliding mode compensator. Simulation and experimental results show that the proposed method realizes dynamics decoupling of gimbal system and enhances system robustness against parameter change and external disturbance. [ABSTRACT FROM AUTHOR]

Abstract: It is shown that the imaging visibility of a two-beam intensity correlated field may be utilized to determine the strength of scattering potential of quasi-homogeneous (QH) media by solutions of the inverse scattering problem provided that both the ratio D/R and the polarization of incident plane waves are known. Analytical descriptions of the methods for the scalar and electromagnetic cases are deduced, respectively. [Copyright &y& Elsevier]

[Display omitted] • Propose an FCN architecture using octave partial convolution and skip connection with scSE (skip-scSE). • Design a novel decoder efficiently using a skip-scSE module. • Design a multi-modal MRI to single MRI modality synthesizing model using proposed FCN as a generator and encoder–decoder discriminator using the cGAN learning approach. • Generate missing modalities for the TCGA dataset using the available modality (or modalities) and predict segmentation using both available and synthesized modalities. • Design a radiogenomic model by combining radiomic features such as intensity, shape, and geometry with gene expression profiling data. The accurate prognosis of glioblastoma multiforme (GBM) plays an essential role in planning correlated surgeries and treatments. The conventional models of survival prediction rely on radiomic features using magnetic resonance imaging (MRI). In this paper, we propose a radiogenomic overall survival (OS) prediction approach by incorporating gene expression data with radiomic features such as shape, geometry, and clinical information. We exploit TCGA (The Cancer Genomic Atlas) dataset and synthesize the missing MRI modalities using a fully convolutional network (FCN) in a conditional generative adversarial network (cGAN). Meanwhile, the same FCN architecture enables the tumor segmentation from the available and the synthesized MRI modalities. The proposed FCN architecture comprises octave convolution (OctConv) and a novel decoder, with skip connections in spatial and channel squeeze & excitation (skip-scSE) block. The OctConv can process low and high-frequency features individually and improve model efficiency by reducing channel-wise redundancy. Skip-scSE applies spatial and channel-wise excitation to signify the essential features and reduces the sparsity in deeper layers learning parameters using skip connections. The proposed approaches are evaluated by comparative experiments with state-of-the-art models in synthesis, segmentation, and overall survival (OS) prediction. We observe that adding missing MRI modality improves the segmentation prediction, and expression levels of gene markers have a high contribution in the GBM prognosis prediction, and fused radiogenomic features boost the OS estimation. [ABSTRACT FROM AUTHOR]

• An underwater fan-wing thruster is tested by towing and self-driving experiments. • Vertical force and velocity are measured at different rotational speeds. • Computational fluid dynamics simulations match the towing experiments. • Unique characteristics are identified, based on experiments and simulations. • Mechanism and unique characteristics are explained, based on a physical model. Fan-wing thrusters are primarily used for aircraft propulsion, but their potential for underwater applications has also been demonstrated. Although many achievements have been made through experimentation, there still remains much work to be done in mechanism and hydrodynamic analyses, especially for the underwater fan-wing thruster (UFT). In this work, experiments are designed and carried out for a UFT. Both self-driving and towing experiments are conducted with a custom-made experiment device. In the self-driving experiments, vertical force and velocity are measured at different rotational speeds of the cross-flow fan. Then, for studying the hydrodynamic performance, specific towing experiments and computational fluid dynamics (CFD) simulations are carried out. Simulation results are in good agreement with the towing experiment results. On the basis of the CFD simulation results, specific unique characteristics are identified. Finally, a physical model is built and analyzed, and the mechanism and distinctive characteristics are explained by the physical model. [ABSTRACT FROM AUTHOR]

Fan-wings, as a form of aircraft propulsion, have shown effectiveness for underwater propulsion. The underwater fan-wing thruster (UFT), which is composed of a fixed-wing and a cross-flow fan under the fixed-wing, can generate significate vertical force underwater. Although some experiments and simulations are carried out to analyze the UFT, the role of the fixed-wing to the UFT has not been researched in depth. In this paper, four parameters: the front opening angle, rear opening angle, upper horizontal length, and incoming flow angle are selected for the role study in four aspects, including vertical force, thrust force, torque, and efficiency. Computational fluid dynamics (CFD) simulations in different rotational speeds of the cross-flow fan and incoming flow velocities conditions are carried out for the UFTs with different parameters, which concurred with towing experiments. Self-driving experiments are also carried out for studying the actual cruise performance of the UFT with different parameters. After that, mechanisms of the effects are analyzed on many velocity magnitude cloud maps from CFD simulation. A physical model is utilized to explain some of the unique fluid phenomena. Finally, the role of the fixed-wing is summarized, and some principle on parameter setting is proposed. • The fixed-wing is abstracted into four parameters, and four characters of underwater fan-wing thruster are discussed. • CFD simulation, experiments, and physical model analyses are carried out. • The fixed-wing can adjust the inflow and outflow to the cross-flow fan, and regulate the number of blades in work. • The fixed-wing can limit the rate and direction of the wake; and affects the formation of some field phenomena. • Some ways to balance the VF and TF and balance the forces and efficiency are proposed. [ABSTRACT FROM AUTHOR]

Abstract: The rapid processing of mass remote sensing data put challenges on computer''s processing capability. Through parallel programming environment based on message passing, parallel K-means unsupervised classification of remote sensing image with different sizes we performed in parallel environment with different computers number. The speedup and efficiency of parallel computation as well as effect of message communication on parallel unsupervised classification were analyzed. The results show that the classification speed of mass amount data parallel remote sensing image unsupervised classification has been greatly improved and the parallel unsupervised classification has effect on parallel efficiency. In the parallel programming, message communication should be minimized as possible and messages should be merged to improve computation efficiency. Rational task allocation and communication can improve performance of parallel computing. [Copyright &y& Elsevier]

Oropharyngeal tumor is traditionally resected from an open approach, often necessitating the need of a midline mandibulotomy in order to remove tumor safely with oncologic margins. The limitations imposed by a transoral route include poor visualization of the inferior extent of the oropharynx, rigid instrumentation, and inability to resect tumor that extends caudally into the supraglottis. While visualization with angled endoscopes, coupled with flexible laser development and microscopic magnification may overcome some of these limitations, this technique suffers from linear trajectory of the instruments which hampers expedient surgical resection in a 3-dimensional fashion. With development of the Da Vinci Surgical System, the safety and oncologic feasibility of removing oropharyngeal tumors are made possible because it provides a 3-dimensional magnification of the surgical field and wristed maneuverability of the surgical instruments which enable surgeons to operate around tight anatomical confines. Nevertheless, this first-generation robot is continually being modified with more flexibility and maneuverability through the development of robots like the FLEX Robotic System and more recently the Da Vinci Single Port System (SP). In this review, we will discuss the historic developments of robots for transoral applications, present the current approved robotic systems, and highlight the upcoming robots for transoral robotic surgery (TORS). Finally, we will also propose an ideal TORS surgical robot by highlighting the engineering technologies to accomplish these challenges. [ABSTRACT FROM AUTHOR]

Glioblastoma multiforme (GBM) are aggressive brain tumors, which lead to poor overall survival (OS) of patients. OS prediction of GBM patients provides useful information for surgical and treatment planning. Radiomics research attempts at predicting disease prognosis, thus providing beneficial information for personalized treatment from a variety of imaging features extracted from multiple MR images. In this study, MR image derived texture features, tumor shape and volumetric features, and patient age were obtained for 163 patients. OS group prediction was performed for both 2-class (short and long) and 3-class (short, medium and long) survival groups. Support vector machine classification based recursive feature elimination method was used to perform feature selection. The performance of the classification model was assessed using 5-fold cross-validation. The 2-class and 3-class OS group prediction accuracy obtained were 98.7% and 88.95% respectively. The shape features used in this work have been evaluated for OS prediction of GBM patients for the first time. The feature selection and prediction scheme implemented in this study yielded high accuracy for both 2-class and 3-class OS group predictions. This study was performed using routinely acquired MR images for GBM patients, thus making the translation of this work into a clinical setup convenient. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the tracking control design for the interval type-2 (IT2) polynomial-fuzzy-model-based (PFMB) control system subject to time-varying delay situation is investigated. The tracking control system is formed of the IT2 polynomial fuzzy model representing a nonlinear system with time-varying delay, the stable reference model and the IT2 polynomial fuzzy controller. The control objective is to design a proper IT2 polynomial fuzzy controller which is capable of driving the states of the polynomial fuzzy model to track those in the reference model and the tracking performance is evaluated and improved by the H ∞ performance index. Also, to handle the uncertainty in the membership functions, the property of IT2 fuzzy sets is utilized to enhance the fuzzy controller’s robustness against uncertainty. In addition, considering the effect of time-varying delay, the Lyapunov–Krasovskii functional based approach is adopted to facilitate the delay-dependent stability analysis. Stability conditions depending on the time-varying delay characteristic with the consideration of H ∞ performance are obtained in terms of sum-of-squares (SOS). Furthermore, the information of the IT2 membership functions is employed in the stability analysis to relax the stability conditions, both membership-function-independent (MFI) and membership-function-dependent (MFD) approaches are presented to develop the stability conditions. Simulation examples are presented to verify the effectiveness of the proposed tracking control approach. [ABSTRACT FROM AUTHOR]

The main purpose of this study was to develop a method for a robust H-infinity control of an unmanned underwater vehicle (UUV) based on the interpolation of the Riccati equation solution. This method combined the robust H-infinity control theory and results of the interpolation of the Riccati equation solution. The UUV's velocity, heading, and depth controllers were derived and obtained. A simulation and experiment in a lake were conducted to verify the effectiveness of the developed controllers. Results indicated that the controllers were feasible, effective, and robust in managing the control of a UUV. [ABSTRACT FROM AUTHOR]

• A novel preparation method for acetone-PMMA and benzene-PMMA coating liquids was developed and demonstrated for manufacturing ultrathin flexible DOEs. • A film-forming technique for ultrathin flexible diffractive optical elements (DOEs) was developed, and the thickness of 2.8μm was achieved for a flexible DOE with home-made benzene-PMMA coating liquid. • An optical device based on a pair of the fabricated DOEs with reciprocating movement was applied for speckle suppression in an experimental imaging system. The speckle contrasts for red, green, and blue lasers decreased to 5%-7%, and the transmittances for DOEs increased to 88%-92%. Compact and flexible optical components are expected to be utilized in laser-imaging systems. We introduce a novel technique for producing self-made ultrathin flexible diffractive optical elements (DOEs) with reciprocating movement that are effective in suppression of laser speckle. We developed a preparation method for acetone-PMMA and benzene-PMMA coating liquids, and obtained all the process parameters for producing ultrathin flexible PMMA DOEs. Experimental results revealed that the fabricated DOEs reduced the speckle contrasts for red, green, and blue lasers substantially; in addition, their transmittance increased significantly. The proposed techniques can be applied extensively in the development of other kind of flexible microoptics. [ABSTRACT FROM AUTHOR]

This paper studies the self-triggered control consensus problem of general linear multi-agent systems(MASs). A novel self-triggered control strategy based on output feedback is proposed for centralized and distributed cases, respectively. In consideration of the states of agents that are not available, a state observer is adopted. A dynamic observer-based control law is employed to improve the transient response. Under this triggering strategy, both the estimated states of MASs and the states of controller are updated at triggering time. The next triggering time is predetermined at the last triggering instant. Moreover, the asymptotic consensus of MASs can be guaranteed. Finally, the effectiveness of the proposed control strategy is illustrated by a numerical example. [ABSTRACT FROM AUTHOR]

Wire-driven flexible robots are efficient devices for minimally invasive surgery, since they can work well in complex and confined environments. However, the real-time position and shape information of the robot cannot be well estimated, especially when there is a payload on the end effector. In this paper, a novel tracking and shape reconstruction method for a wire-driven flexible robot is proposed. The proposed method utilizes the length of the robot as well as the positional and directional information measured by an electromagnetic sensor mounted at the distal end of the robot. A reconstruction algorithm, which is based on a three order Bézier curve, is then carried out utilizing the positional and directional information along with the length information of the robot. This method can provide good tracking results and high shape reconstruction accuracy with limited modification of the robot. Compared with other reconstruction methods, the proposed method does not rely on any mechanical model of the robot. Therefore, the method works well with an unknown payload. The feasibility of the proposed method is verified by both simulation and experimental results. [ABSTRACT FROM AUTHOR]

The underwater fan-wing thruster (UFT), which is composed of a fixed wing and a cross-flow fan (CFF) under the fixed wing, has excellent underwater propulsion performance, especially for vertical propulsion. Despite prior experiments and simulations in analyzing the UFT, the effects of the CFF on the performance of the UFT have not been studied in depth. In this paper, the hydrodynamic and acoustic performance of UFT is studied by computational fluid dynamics (CFD) simulations with different CFF parameters, including the number of blades, internal to external diameter ratio, internal blade angles, and external blade angles. Towing experiments are also carried out for verification. Based on cloud and vector maps generated by CFD, the effect mechanisms of parameter variation are also analyzed. The effects of CFF on the UFT are finally summarized, and the best sets of parameters are discussed based on the real working conditions of UFTs. • The cross-flow fan is abstracted into four parameters. • Hydrodynamic and acoustic characters of underwater fan-wing thruster are discussed. • CFD simulation, experiments are carried out. • Smooth across flow of the CFF determines the hydrodynamic performance of the UFT. • The number of blades is the most critical parameter affecting acoustic performance. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we investigate the dispersion and polarization properties of photonic crystal fiber with one ring or more rings of elliptical air-holes using plane-wave expansion (PWE) method. By introducing three rings of elliptical air-holes, PCF with ultra-low and ultra-flattened dispersion is designed and a total dispersion curve between ±0.5ps/nm/km from 1315 to 1855nm wavelength range is demonstrated. Furthermore, the polarization property of these elliptical air-hole-containing PCFs is analyzed and the variation of the birefringence with the area and ellipticity of the elliptical air-holes are discussed. [Copyright &y& Elsevier]

Abstract: The effects of pump noise on noise characteristics of single-pump and two-pump fiber optical parametric amplifiers (FOPAs) are analyzed theoretically. The results show that the increased noise of FOPAs caused by the pump noise is related to the structural parameters of amplifiers. Therefore, the structural parameters of FOPAs should be optimized to balance the conflicting requirement of high gain and low noise. [Copyright &y& Elsevier]