Search

Blue quantum dot (QD) light emitting diode (QLED) developments are far lagging behind the red and green ones as it becomes difficult to balance charge injection and photo stability than the latter. Here, we introduced a combination of a low band energy shell with better surfactants, which largely meet both abovementioned requirements. Our simulation pinpoints that it is the exposed Se on the QD surface, which causes non-radiative relaxations. By adding tributyl phosphine (TBP), which is a good ligand to Se, we recover photoluminescence quantum yield (PLQY) from less than 8.0% up to above 85.0%. The corresponding external quantum efficiency (EQE) of QLEDs increases from 3.1% to 10.1%. This demonstrates that the low bandgap shell with effective surfactant passivation is a promising strategy to enhance QLED performance.

Motion control strategies of currently available bioprinters are mainly based on the Cartesian coordinate system to perform layer-by-layer stacking of materials along the vertical direction through the axial-aligned horizontal slicing method. The stacked bioprinting strategy that is inconsistent with the growing pattern of natural biological tissues/organs with anisotropic property in some sense, is stimulating new bioprinting techniques such as the stereotactic bioprinting. This paper analytically calculates the forward and inverse kinematics of a four degree-of-freedom (4-DOF) robotic bioprinter prototype developed in our group which is featured with a 3-DOF manipulator and a 1-DOF circular rail for stereotactic bioprinting. Numerical simulations of working space and motion characteristics using MATLAB and V-REP software have validated the performance and feasibility of the developed prototype, which provides a robot-assisted solution reference for the stereotactic bioprinting.

The calibration of binocular infrared camera is a key step to realize the positioning of infrared camera. The existing methods of binocular camera calibration are not suitable for infrared camera, so it is necessary to study the methods of binocular infrared camera calibration and positioning. In this paper, a calibration and positioning method of binocular infrared camera is proposed, and the infrared positioning of two kinds of objects is completed by using this method. Firstly, a special temperature calibration system is used to collect the images for binocular calibration, then the center point detection algorithm and Zhang’s calibration method are used to process the infrared calibration image to obtain the internal and external parameters of the binocular infrared camera. The calibration error is compared with that of binocular visible camera to prove the feasibility of the binocular infrared camera calibration. Secondly, according to the calibrated parameter matrix of the binocular infrared camera, symmetrical circle calibration object detection algorithm and coordinate transformation are carried out for the distortion correction images to achieve infrared positioning of different objects, and the positioning error is obtained. The results show that the calibration method of binocular infrared camera is feasible, and it has more functions than the traditional calibration method.

Anal center detection is of great significance for the diagnosis of anorectal diseases, for accurate anal center detection can help gastrointestinal (GI) robot enter the human body automatically and check the patient’s anal and lower intestinal diseases, which is the first step to realize autonomous diagnosis. However, there is no available result on the anal center detection. In this work, the superpixel method is employed to find the anal center. In the first step, the collected image dataset is expanded through the data augmentation method. In the second step, we use the superpixel segmentation method, a machine learning algorithm, to segment the image by pixels with similar features in the image. Then we determine the region of interest (ROI) based on the threshold and the size of the connected region. After that, the gray barycenter method is used to determine the center of gravity of the ROI i.e., the anal center. The ground-truth anal center is obtained by the average of the anal center coordinates determined by ten anorectal surgeons. By the proposed algorithm, it is found that the ROI detected in 70.59% of the images in the dataset includes the anal center, and the positioning accuracy of the anal center is 88.87% averagely. Thus, the method can provide the anal center for GI robot.

In this paper, we address the problem of fully automatic labeling and segmentation of 3D vertebrae in arbitrary Field-Of-View (FOV) CT images. We propose a deep learning-based two-stage solution to tackle these two problems. More specifically, in the first stage, the challenging vertebra labeling problem is solved via a novel transformers-based 3D object detector that views automatic detection of vertebrae in arbitrary FOV CT scans as a one-to-one set prediction problem. The main components of the new method, called Spine-Transformers, are a one-to-one set based global loss that forces unique predictions and a light-weighted 3D transformer architecture equipped with a skip connection and learnable positional embeddings for encoder and decoder, respectively. We additionally propose an inscribed sphere-based object detector to replace the regular box-based object detector for a better handling of volume orientation variations. Our method reasons about the relationships of different levels of vertebrae and the global volume context to directly infer all vertebrae in parallel. In the second stage, the segmentation of the identified vertebrae and the refinement of the detected centers are then done by training one single multi-task encoder-decoder network for all vertebrae as the network does not need to identify which vertebra it is working on. The two tasks share a common encoder path but with different decoder paths. Comprehensive experiments are conducted on two public datasets and one in-house dataset. The experimental results demonstrate the efficacy of the present approach.

The low efficiency and fast degradation of devices from ink-jet printing process hinders the application of quantum dot light emitting diodes on next generation displays. Passivating the trap states caused by both anion and cation under-coordinated sites on the quantum dot surface with proper ligands for ink-jet printing processing reminds a problem. Here we show, by adapting the idea of dual ionic passivation of quantum dots, ink-jet printed quantum dot light emitting diodes with an external quantum efficiency over 16% and half lifetime of more than 1,721,000 hours were reported for the first time. The liquid phase exchange of ligands fulfills the requirements of ink-jet printing processing for possible mass production. And the performance from ink-jet printed quantum dot light emitting diodes truly opens the gate of quantum dot light emitting diode application for industry., Designing efficient and scalable quantum dot LEDs meeting industrial requirements remains a challenge. Here, the authors, by leveraging the liquid phase exchange of d-MX2 ligands, present printed quantum dot LEDs with external quantum efficiency over 16% and half lifetime of more than 1,721,000 hours.

Clinical-oriented robot configuration and data-driven artificial intelligence is evolving robotic orthopedics. This chapter summarizes the harmonious collaboration trend among surgeon–robot–environment interaction in the OR from aspects of the rigid–flexible–soft hybrid mechanical configuration and the environmental structurization, the data-driven trend from aspects of the surgical data science idea, and the artificial intelligence applications in the orthopedics.

Due to the huge reserves and great commercial potential of No. A group coal seam, the study on its thermal properties and combustion kinetics have attracted much attention. Via thermogravimetric (TG) analysis, the combustion characteristics and kinetics of No. A 3 coal were studied with three types of coal samples, with the grain diameter less than 200 meshes, 200~100 meshes, 100~60meshes, seperately. Under three characteristic temperatures such as T t , T p and T b , the whole combustion process could be roughly divided into 4 stages. Combined with the T max and T i , these five characteristic temperatures increase with elevating heating rates. The Kissinger-Akahira-Sunose (KAS) method and Flynn-Wall-Ozawa (FWO) method as reliable methods were used to verify the results of activation energy ( E a ) determined by of model-fitting methods. As complementary, the Coats-Redfern method was used to calculate the pre-exponential factor ( A ) and the correlation coefficient ( R 2 ). According to the evaluation criteria of E a and R 2 , D1 mechanism was the most probable model to depict the combustion kinetics.

The hand-eye calibration is used to determine the transformation between the end-effector and the camera marker of the robot. But the robot movement in traditional method would be time-consuming, inaccurate and even unavailable in some conditions. The method presented in this article can complete the calibration without any movement and is more suitable in clinical applications.Instead of solving the classic non-linear equation AX = XB, we collected the points on X and Y axes of the tool coordinate system (TCS) with the visual probe and fitted them using the singular value decomposition algorithm (SVD). Then, the transformation was obtained with the data of the tool center point (TCP). A comparison test was conducted to verify the performance of the method.The average translation error and orientation error of the new method are 0.12 ± 0.122 mm and 0.18 ± 0.112° respectively, while they are 0.357 ± 0.347 mm and 0.416 ± 0.234° correspondingly in the traditional method.The high accuracy of the method indicates that it is a good candidate for medical robots, which usually need to work in a sterile environment.

Early prediction is one of the key technologies to the prevention and extinguishment of spontaneous combustion of coal. The aim of this study was to propose a type of scientific and convenient forecasting indicator for initial spontaneous combustion of coal in the gob area. The authors developed the calculation model of carbon monoxide (CO) concentration in the air return corner based on the generation mechanism, sources, and influencing factors of CO. The parameters obtained from both large-scale coal self-heating experiment and in-situ observation of four collieries in Yuanyang lake mine area were used to calculate the extreme value of CO concentrations on various stages of spontaneous combustion. The established indicators were applied to specific coal mine scenarios and combined with the in-situ measurements. It demonstrates that this method has provided the scientific guidance for safer exploitation on coal mines. Furthermore, the main reasons of unstable CO concentrations in the return corne...

GaAs is one of the most important semiconductors. However, colloidal GaAs nanocrystals remain largely unexplored because of the difficulties with their synthesis. Traditional synthetic routes either fail to produce pure GaAs phase or result in materials whose optical properties are very different from the behavior expected for quantum dots of direct-gap semiconductors. In this work, we demonstrate a variety of synthetic routes toward crystalline GaAs NCs. By using a combination of Raman, EXAFS, transient absorption, and EPR spectroscopies, we conclude that unusual optical properties of colloidal GaAs NCs can be related to the presence of Ga vacancies and lattice disorder. These defects do not manifest themselves in TEM images and powder X-ray diffraction patterns but are responsible for the lack of absorption features even in apparently crystalline GaAs nanoparticles. We introduce a novel molten salt based annealing approach to alleviate these structural defects and show the emergence of size-dependent excitonic transitions in colloidal GaAs quantum dots.

Application of 3D printing in the individualized fabrication of biological organ receives more and more attentions. The adopted movement trajectories of nozzle in 3D printing are all based on depositing materials vertically layer by layer. We noticed that the biological organ has always anisotropic property and its natural growing procedure implies a so-called stereotactic fabrication method which can be implemented utilizing robotic techniques. In this research, we proposed and simulated a robot-assisted stereotactic printing method. Kinematics analysis of the robotic manipulator was analyzed. Trajectory planning method for stereotactic operation was designed. Motion simulation analysis of the planned trajectory utilizing manipulator was conducted which validated effectiveness of the proposed printing system from aspects of motion accuracy, flexibility, and potential collisions. The results indicated flexibility of the proposed robot-assisted stereotactic printing technology.

Impurity doping has been widely used to endow semiconductor nanocrystals with novel optical, electronic, and magnetic functionalities. Here, we introduce a new family of doped NCs offering unique insights into the chemical mechanism of doping, as well as into the fundamental interactions between the dopant and the semiconductor host. Specifically, by elucidating the role of relative bond strengths within the precursor and the host lattice, we develop an effective approach for incorporating manganese (Mn) ions into nanocrystals of lead-halide perovskites (CsPbX3, where X = Cl, Br, or I). In a key enabling step not possible in, for example, II–VI nanocrystals, we use gentle chemical means to finely and reversibly tune the nanocrystal band gap over a wide range of energies (1.8–3.1 eV) via postsynthetic anion exchange. We observe a dramatic effect of halide identity on relative intensities of intrinsic band-edge and Mn emission bands, which we ascribe to the influence of the energy difference between the cor...

The test method and principle that isothermal difference leading the elevated temperature experiment and the large coal spontaneous ignition experiment are different, data acquisition methods are also different, the content and calculation basis of coal spontaneous combustion characterization parameters and solution are slightly different. In order to realize the comparative analysis of isothermal difference leading experiment and large coal spontaneous combustion experiment, it selects samples of Zhaoxian Coal Mine to conduct large coal spontaneous combustion experiment (defined as ZXDY) and isothermal difference leading experiment (defined as ZXYM), and to make an analysis of the characterization parameters of coal spontaneous combustion, obtaining the characteristics and applicability of the two experimental methods of coal spontaneous combustion characterization parameters.

In this paper, we present a method for automatic segmentation of lumbar vertebrae from a given lumbar spinal CT image. More specifically, our automatic lumbar vertebrae segmentation method consists of two steps: affine atlas-target registration-based label fusion and bone-sheetness assisted multi-label grid cut which has the inherent advantage of automatic separation of the five lumbar vertebrae from each other. We evaluate our method on 21 clinical lumbar spinal CT images with the associated manual segmentation and conduct a leave-one-out study. Our method achieved an average Dice coefficient of 93.9 ± 1.0% and an average symmetric surface distance of 0.41 ± 0.08 mm.

The use of semiconductor nanocrystal quantum dots (QDs) in optoelectronic devices typically requires postsynthetic chemical surface treatments to enhance electronic coupling between QDs and allow for efficient charge transport in QD films. Despite their importance in solar cells and infrared (IR) light-emitting diodes and photodetectors, advances in these chemical treatments for lead chalcogenide (PbE; E = S, Se, Te) QDs have lagged behind those of, for instance, II-VI semiconductor QDs. Here, we introduce a method for fast and effective ligand exchange for PbE QDs in solution, resulting in QDs completely passivated by a wide range of small anionic ligands. Due to electrostatic stabilization, these QDs are readily dispersible in polar solvents, in which they form highly concentrated solutions that remain stable for months. QDs of all three Pb chalcogenides retain their photoluminescence, allowing for a detailed study of the effect of the surface ionic double layer on electronic passivation of QD surfaces, which we find can be explained using the hard/soft acid-base theory. Importantly, we prepare highly conductive films of PbS, PbSe, and PbTe QDs by directly casting from solution without further chemical treatment, as determined by field-effect transistor measurements. This method allows for precise control over the surface chemistry, and therefore the transport properties of deposited films. It also permits single-step deposition of films of unprecedented thickness via continuous processing techniques, as we demonstrate by preparing a dense, smooth, 5.3-μm-thick PbSe QD film via doctor-blading. As such, it offers important advantages over laborious layer-by-layer methods for solar cells and photodetectors, while opening the door to new possibilities in ionizing-radiation detectors.

3D printing (3DP) is becoming a research and development focus in nanobiomaterials as it can quickly and accurately fabricate any desired 3D tissuemodel only if itssize is appropriate. The different material powders (with different dimensional scales) and the printing strategies are the most direct factors influencing 3DP quality. With the development of nanotechnologies, 3DP is adopted more frequently for its rapidness in fabrication and precision in geometry. The fabrication in micro/nanoscale may change the performance of biomaterials and devices because it can retain more anisotropy of biomaterials compared with the traditionally rapid prototyping techniques. Thus, the biosafety issue is especially concerned by many researchers and is investigated in performance and safety of biomaterials and devices. This paper investigates the performance of 3DP in fabrication of nanobiomaterials and devices so as to partially explain how 3DP influences the performance and safety of nanobiomaterials.

Background Efficiency evaluation is important for expanding the acceptance and deployment of medical robots, but it is still an open issue. In this study, a data envelopment analysis (DEA)-based method was proposed and implemented with a novel robotic system for femoral neck surgery. Methods Femoral neck surgeries with and without the assistance of the robotic system were modelled as decision-making units (DMUs). C2R model was chosen to calculate the relative efficiency. Results Clinical simulation experiments were performed with 12 Sawbone models and 24 cadaveric femurs, and 19 clinical cases were chosen to be the control group. The minimum value of the robotically assisted surgery was 1, and the minimum value of the traditional surgery was 0.741535, demonstrating the efficiency of the robotic system. Conclusion This research showed that DEA-based efficiency evaluation is practical for medical robotic systems. Copyright © 2009 John Wiley & Sons, Ltd.

We examine the stability of excitons in quantum-confined InP nanocrystals as a function of temperature elevation up to 800 K. Through the use of static and time-resolved spectroscopy, we find that small inorganic capping ligands substantially improve the temperature dependent photoluminescence quantum yield relative to native organic ligands and perform similarly to a wide band gap inorganic shell. For this composition, we identify the primary exciton loss mechanism as electron trapping through a combination of transient absorption and transient photoluminescence measurements. Density functional theory indicates little impact of studied inorganic ligands on InP core states, suggesting that reduced thermal degradation relative to organic ligands yields improved stability; this is further supported by a lack of size dependence in photoluminescence quenching, pointing to the dominance of surface processes, and by relative thermal stabilities of the surface passivating media. Thus, small inorganic ligands, which benefit device applications due to improved carrier access, also improve the electronic integrity of the material during elevated temperature operation and subsequent to high temperature material processing.

Almost all navigation systems have incorporated binocular vision-based tracking function, thus the investigation of binocular vision-based surgical planning can effectively improve the operation accuracy and efficiency. In order to integrate better human-computer interactions, an interactive path planning procedure for 2D fluoroscopy-based intramedullary nailing of bone fracture is proposed, which emphasizes on the interactive selection of end points of target path (3D line segment) on only two arbitrary projection images for navigation. The 3D line segment can be calculated by these selected end points. After introduction of planning and navigating algorithm, the characteristics of this planning procedure is discussed, and experimental tests are conducted in the navigation module of the HybriDot robotic system. The results showed the feasibility of the planning procedure.

Feature correspondence is one of the essential difficulties in image processing, given that it is applied within a wide range in computer vision. Even though it has been studied for many years, feature correspondence is still far from being ideal. This paper proposes a multigeometric-constraint algorithm for finding correspondences between two sets of features. It does so by considering interior angles and edge lengths of triangles formed by third-order tuples of points. Multigeometric-constraints are formulated using matrices representing triangle similarities. The experimental evaluation showed that the multigeometric-constraint algorithm can significantly improve the matching precision and is robust to most geometric and photometric transformations including rotation, scale change, blur, viewpoint change, and JPEG compression as well as illumination change. The multigeometric-constraint algorithm was applied to object recognition which includes extraprocessing and affine transformation. The results showed that this approach works well for this recognition.

Background Spatial positioning is the key function of a surgical navigation robot system, and accuracy is the most important performance index of such a system. Methods The kinematic parameters of a six degrees of freedom (DOF) robot arm were used to form the transformation from intraoperative fluoroscopy images to a robot's coordinate system without C-arm calibration and to solve the redundant DOF problem. The influences of three typical error sources and their combination on the final navigation error were investigated through Monte Carlo simulation. Results The navigation error of the proposed method is less than 0.6 mm, and the feasibility was verified through cadaver experiments. Error analysis suggests that the robot kinematic error has a linear relationship with final navigation error, while the image error and gauge error have nonlinear influences. Conclusions This kinematic parameters based method can provide accurate and convenient navigation for orthopedic surgeries. The result of error analysis will help error design and assignment for surgical robots.

We report the colloidal synthesis of monodisperse nanocrystals (NCs) of InSb, which is an important member of III-V semiconductor family. Colloidal InSb NC quantum dots showed well-resolved excitonic transitions in the near-infrared spectral range, with the optical band gaps tunable from ∼1.03 eV (1200 nm) to ∼0.71 eV (1750 nm) corresponding to 3.3 and 6.5 nm InSb NCs, respectively. We observed size-tunable band edge photoluminescence that could be significantly enhanced by growing InSb/CdSe or InSb/CdS core-shell nanostructures. Films of InSb NCs capped with S(2-) ions showed ambipolar charge transport.

NMI (network management interfaces) are important part of network management system. The conformance testing of NMI is an important mean to ensure interconnection, inter-working, interoperability among management systems. In order to complete complex function or service test for NMI, a series of test cases must be organized together with logical relationship to compose test transaction. Using test transaction to execute test automatically can improve test efficiency and reduce test cost. Currently, test transaction is described by script format and can not support visual edit. This paper presents a Graphical Presentation Format to describe test transaction so that test transaction is easily edited and showed flexibility.

Entry position of the graft is very important in anterior cruciate ligament (ACL) reconstruction. However the determination of entry position is very difficult to the surgeon. In this paper, a navigation and evaluation system assisted by the 6-DOFS robot is implemented for the simulation evaluation and planning insertion points based on quadrant method for the femur and Staublis method for the tibia on the lateral X-ray image of knee joint. Meanwhile, the implementation of the key technologies such as image correction, image registration, C-arm calibration, video tracking, bone surface reconstruction, image fusion, 6-DOFS robot, and virtual simulation are introduced. Finally, Experiments about the tunnel planning method and real time tracking of surgical apparatus are implemented on 8 bone of plastic models (Sawbone, Swiss) and 10 bones of the goat. In the experiment, the tibia rotates around the femur under the surgeon's implementation to evaluate the planning result with the virtual simulation and evaluation module. The positioning error is 1.59mm from analysis on 30 space targets. The virtual reconstruction ACL is satisfied with two important criteria of the best isometry and collision detection between graft and intercondylar surface of femur. The results are well accepted in operations. In order to satisfying with the request of exact operation in ACL reconstruction, we have developed 6-DOFS passive robot to assist the surgeons entry positioning and drilling of implant tunnels, implementing exact operation in knee joint.