1,485 research outputs found
Highly Durable Oxygen Reduction Reaction Electrocatalyst with Uniformly Distributed Platinum Nanoparticles in a 3D Bicontinuous and Hollow N-doped Carbon Support
No full textSimultaneous Optimization of Patient-Image Registration and Hand-Eye Calibration for Accurate Augmented Reality in Surgery
No full textObjective: Augmented reality (AR) navigation using a position sensor in endoscopic surgeries relies on the quality of patient-image registration and hand-eye calibration. Conventional methods collect the necessary data to compute two output transformation matrices separately. However, the AR display setting during surgery generally differs from that during preoperative processes. Although conventional methods can identify optimal solutions under initial conditions, AR display errors are unavoidable during surgery owing to the inherent computational complexity of AR processes, such as error accumulation over successive matrix multiplications, and tracking errors of position sensor. Methods: We propose the simultaneous optimization of patient-image registration and hand-eye calibration in an AR environment before surgery. The relationship between the endoscope and a virtual object to overlay is first calculated using an endoscopic image, which also functions as a reference during optimization. After including the tracking information from the position sensor, patient-image registration and hand-eye calibration are optimized in terms of least-squares. Results: Experiments with synthetic data verify that the proposed method is less sensitive to computation and tracking errors. A phantom experiment with a position sensor is also conducted. The accuracy of the proposed method is significantly higher than that of the conventional method. Conclusion: The AR accuracy of the proposed method is compared with those of the conventional ones, and the superiority of the proposed method is verified. Significance: This study demonstrates that the proposed method exhibits substantial potential for improving AR navigation accuracy. © 1964-2012 IEEE.1
Hybrid dual full-bridge DC-DC converter with reduced circulating current, output filter and conduction loss of rectifier stage for RF power generator application
No full textIn this paper, a hybrid dual full-bridge DC-DC converter for radio-frequency (RF) power generator application is proposed to overcome the drawbacks of conventional phase-shift full-bridge (PSFB) converter such as large circulating current of primary side and large output filter size. The proposed converter adopts dual full-bridge hybrid structure with a small series capacitor in the primary side and full-bridge rectifier with two additional low-voltage-rated diodes in the secondary side. With this structure, the proposed converter has advantages of reduction of circulating current, zero-voltage switching (ZVS) operation of all primary switches, size reduction of output inductor, and low conduction loss of rectifier stage. Furthermore, the proposed converter can regulate the output voltage very wide by changing the operational mode according to the output voltage. These advantages result in the improvement of whole load efficiency. The operational principle and analysis of proposed converter are presented and analyzed. A 3kW 40-200V output laboratory prototype is designed and built to verify the feasibility and the effectiveness of the proposed converter
Augmented reality-based electrode guidance system for reliable electroencephalography
No full textAbstract Background In longitudinal electroencephalography (EEG) studies, repeatable electrode positioning is essential for reliable EEG assessment. Conventional methods use anatomical landmarks as fiducial locations for the electrode placement. Since the landmarks are manually identified, the EEG assessment is inevitably unreliable because of individual variations among the subjects and the examiners. To overcome this unreliability, an augmented reality (AR) visualization-based electrode guidance system was proposed. Methods The proposed electrode guidance system is based on AR visualization to replace the manual electrode positioning. After scanning and registration of the facial surface of a subject by an RGB-D camera, the AR of the initial electrode positions as reference positions is overlapped with the current electrode positions in real time. Thus, it can guide the position of the subsequently placed electrodes with high repeatability. Results The experimental results with the phantom show that the repeatability of the electrode positioning was improved compared to that of the conventional 10–20 positioning system. Conclusion The proposed AR guidance system improves the electrode positioning performance with a cost-effective system, which uses only RGB-D camera. This system can be used as an alternative to the international 10–20 system
A new cell-to-cell balancing circuit with a center-cell concentration structure for series-connected batteries
No full textA bidirectional cell-to-cell balancing structure using two switches per each cell shows good balancing ability, but many switches lead to increase of the cost and size. To reduce the number of switches, this paper proposes a new cell-to-cell balancing circuit with a center-cell concentration structure. The proposed circuit collects the charges of the overcharged cell into the center-cell, and then the collected charges are redistributed to the other cells. The proposed circuit has unidirectional balancing structure with single switch per each cell, but it can achieve competitive balancing ability compared to bidirectional structure. In this paper, the operational principles of the proposed circuit are analyzed, and the comparison between the proposed and conventional circuits is shown. To verify the validity of the proposed circuit, experiment with 8 batteries is carried out, and the experimental results show the improved cell balancing ability although one switch is used per each cell
이차 전지용 고용량 고성능 Zr계 수소 저장 합금
No full textA hydrogen storage alloy, represented by the following formula I which is suitable for use as an active anode material for ni-metal hydride secondary cells by virtue of its high discharge characteristics including, for example, a discharge capacity ranging from approximately 300 to 400 mAh/g and a rate capability of at least 80%; Zr12212#xtix(MnuVvNiy)z2003#2003#I wherein, x, u, v, and z each represent an atom fraction under the condition of: 0003c#x0.2, 1.5u0.7, 0.5v0.7, 1.0y1.4, and 0.84z1.0.1
역률개선을 위한 자기에너지 궤환기법의 간단한 삼상 단일전력단 AC/DC 컨버터
No full textA simple three-phase single-stage AC/DC forward converter with transformer magnetic energy feedback technique for power factor correction is proposed. The operational principle of the proposed converter is presented. The proposed converter gives the good power factor correction, low line current harmonic distortions, and tight output voltage regulation. The prototype shows high power power factor with low line current harmonics
Modularized Charge Equalization Converter for Hybrid Electric Vehicle Lithium-ion Battery Stack
No full textModularized charge equalization converter for HEV lithium-ion battery cells is proposed in this paper, in which intra-module and inter-module charge equalization can be achieved at the same time. For intra-module charge equalization, the conventional flyback DC/DC converters of low power and small size are employed, in which all of the primary sides are coupled in parallel for selective charge of the specific under charged cell within the module. For inter-module charge equalization, the flyback DC/DC converters are also added, in which all the secondary windings are electrically linked in parallel for automatic charge balancing among the modules. An engineering sample of forty cells hiring the proposed cell balancing scheme is implemented and its experimental result shows that the proposed modularized charge equalization circuit has good cell balancing performance
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