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排序方式: 共有286条查询结果,搜索用时 15 毫秒
61.
62.
Benoit Huard Mathieu Grossard Sandrine Moreau Thierry Poinot 《Control Engineering Practice》2013,21(9):1178-1187
This paper proposes a multi-model based approach that estimates joint position and collision detection of a lightweight electric actuator dedicated to manipulation tasks. Taking advantage of an optimized back-drivable mechatronic design, the use of proprioceptive measures at the motor level enables the estimation of the unmeasured terminal position of the mechanical motor-to-joint transmission and force contact disturbance. A polytopic formulation is introduced based on an accurate model of the mechatronic transmission. Then, a multi-model observer-based estimator is synthesized using root-clustering for exteroceptive variables estimation without additional position/force sensor. The approach is experimentally validated with a single degree-of-freedom manipulator. 相似文献
63.
P. K. Johnny Wong Elmer van Geijn Wen Zhang Anton A. Starikov T. Lan Anh Tran Johnny G. M. Sanderink Martin H. Siekman Geert Brocks Paul J. Kelly Wilfred G. van der Wiel Michel P. de Jong 《Advanced functional materials》2013,23(39):4933-4940
Structurally ordered interfaces between ferromagnetic electrodes and graphene or graphite are of great interest for carbon spintronics, since they allow spin‐filtering due to k‐vector conservation. By solid phase epitaxy of amorphous/nanocrystalline CoFeB at elevated temperatures, the feasibility of fabricating crystalline interfaces between a 3d ferromagnetic alloy and graphite is demonstrated, without suffering from the unwetting problem that was commonly seen in many previous studies with 3d transition metals. The films fabricated on graphite in this way are found to have a strong body‐centered‐cubic (110) texture, albeit without a unique, well‐defined in‐plane epitaxial relationship with the substrate lattice. Using various X‐ray spectroscopic techniques, it is shown that boron suppresses the formation of CoFe‐O during CoFeB deposition, and then diffuses out of the CoFe lattice. Segregation of B occurred exclusively to the film surface upon in situ annealing, and not to the interface between CoFeB and graphite. This is favorable for obtaining a high spin polarization at the hybrid CoFe/graphite crystalline interface. The Co and Fe spin moments in the crystalline film, determined by X‐ray magnetic circular dichroism, are found to be bulk‐like, while their orbital moments show an unusual giant enhancement which has yet to be understood. 相似文献
64.
Large‐Scale Synthesis of Freestanding Layer‐Structured PbI2 and MAPbI3 Nanosheets for High‐Performance Photodetection
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Changyong Lan Ruoting Dong Ziyao Zhou Lei Shu Dapan Li SenPo Yip Johnny C. Ho 《Advanced materials (Deerfield Beach, Fla.)》2017,29(39)
Recently, due to the possibility of thinning down to the atomic thickness to achieve exotic properties, layered materials have attracted extensive research attention. In particular, PbI2, a kind of layered material, and its perovskite derivatives, CH3NH3PbI3 (i.e., MAPbI3), have demonstrated impressive photoresponsivities for efficient photodetection. Herein, the synthesis of large‐scale, high‐density, and freestanding PbI2 nanosheets is demonstrated by manipulating the microenvironment during physical vapor deposition. In contrast to conventional two‐dimensional (2D) growth along the substrate surface, the essence here is the effective nucleation of microplanes with different angles relative to the in‐plane direction of underlying rough‐surfaced substrates. When configured into photodetectors, the fabricated device exhibits a photoresponsivity of 410 mA W?1, a detectivity of 3.1 × 1011 Jones, and a fast response with the rise and decay time constants of 86 and 150 ms, respectively, under a wavelength of 405 nm. These PbI2 nanosheets can also be completely converted into MAPbI3 materials via chemical vapor deposition with an improved photoresponsivity up to 40 A W?1. All these performance parameters are comparable to those of state‐of‐the‐art layered‐material‐based photodetectors, revealing the technological potency of these freestanding nanosheets for next‐generation high‐performance optoelectronics. 相似文献
65.
We present a system for constructing 3D models of real-world objects with optically challenging surfaces. The system utilizes a new range imaging concept called multi-peak range imaging, which stores multiple candidates of range measurements for each point on the object surface. The multiple measurements include the erroneous range data caused by various surface properties that are not ideal for structured-light range sensing. False measurements generated by spurious reflections are eliminated by applying a series of constraint tests. The constraint tests based on local surface and local sensor visibility are applied first to individual range images. The constraint tests based on global consistency of coordinates and visibility are then applied to all range images acquired from different viewpoints. We show the effectiveness of our method by constructing 3D models of five different optically challenging objects. To evaluate the performance of the constraint tests and to examine the effects of the parameters used in the constraint tests, we acquired the ground truth data by painting those objects to suppress the surface-related properties that cause difficulties in range sensing. Experimental results indicate that our method significantly improves upon the traditional methods for constructing reliable 3D models of optically challenging objects. 相似文献
66.
Ashwin?Natarajan Ying?CaiEmail author Johnny?Wong 《Multimedia Tools and Applications》2009,43(2):179-193
Periodic broadcast is a cost-effective solution for large-scale distribution of popular videos. Regardless of the number of
video requests, this strategy guarantees a constant worst service latency to all clients, making it possible to serve a large
community with a minimal amount of broadcast bandwidth. Although many efficient periodic broadcast techniques have been proposed,
most of them impose rigid requirements on client receiving bandwidth. They either demand clients to have the same bandwidth
as the video server, or limit them to receive no more than two video streams at any one time. In our previous work, we addressed
this problem with a Client-Centric Approach (CCA). This scheme takes into consideration both server broadcast bandwidth and client receiving bandwidth and allows clients
to use all their receiving capability for prefetching broadcast data. As a result, given a fixed broadcast bandwidth, a shorter
broadcast period can be achieved with an improved client communication capability. In this paper, we present an enhanced version
of CCA to further leverage client bandwidth for more efficient video broadcast. The new scheme reduces the broadcast latency
up to 50% as compared to CCA. We prove the correctness of this new technique and provide an analytical evaluation to show
its performance advantage as compared with some existing techniques.
相似文献
Johnny WongEmail: |
67.
Kristin Guldbrandsen Froysa Johnny Froyen Magne S. Espedal 《Computing and Visualization in Science》2000,3(3):121-131
Recently an operator splitting technique for convection diffusion equations, originating in porous medium flow, has been developed
and analysed for one and two space dimensional models. The method is based on a solution of a modified hyperbolic problem
which is used to approximate the original equation in a second step. The main objective of this paper is to investigate these
algorithms for three dimensional porous media models, where handling of the gravity term is a main issue. The balance between
the external pressure and the gravity may give a velocity field which is vanishing and may change sign in parts of the computational
domain. This type of problem is dificult to solve accurately. Two different solution approaches are tested for accuracy, stability
and computational costs.
Received: 29 June 1998 / Accepted: 11 February 2000 相似文献
68.
Sen Zhang Pingdan Xiao Xitong Hong Ruohao Hong Chang Liu Qianlei Tian Wanhan Su Chao Ma Xingqiang Liu Kenli Li Johnny C. Ho Yawei Lv Qinghui Hong Lei Liao Xuming Zou 《Advanced functional materials》2023,33(44):2306173
Metal oxide semiconductors (MOSs) are considered as potential candidates for the low-cost, large-area fabrication of flexible optoelectronic devices. However, the current optoelectronic devices based on MOSs are limited to unidirectional photoresponse, which constrains the performance of MOSs-based vision sensors for artificial vision systems. Herein, for the first time, a flexible artificial vision system integrated with optical perception, computation, and learning functionalities is demonstrated using SnO optoelectronic synaptic transistor-based event-driven vision sensors to enable dynamic image perception, noise reduction, detection, and recognition. Specifically, an ambipolar SnO transistor is demonstrated by introducing HfO2 passivation layer, which facilitates the movement of O atoms around Sn-vacancy sites to the HfO2 layer to achieve the transformation from p-type to ambipolar transport behaviors. More importantly, the HfO2-passivated SnO transistors exhibit gate-tunable bidirectional photoresponse behavior, which is essential to simulate the neurobiological functionalities of bipolar cells. This way, the multilayer neural network learning circuit built from SnO transistors achieves fast recognition at a 16% Gaussian noise level and high recognition accuracy up to 95.2% for pattern letters. Under the bending states, recognition accuracies are still retained at 91.2%. These properties are well retained even under the influence of 100% offset of the synaptic programming value. 相似文献
69.
Pengshan Xie Xu Chen Zixin Zeng Wei Wang You Meng Zhengxun Lai Quan Quan Dengji Li Weijun Wang Xiuming Bu Sai-Wing Tsang SenPo Yip Jia Sun Johnny C. Ho 《Advanced functional materials》2023,33(4):2209091
The visual system, one of the most crucial units of the human perception system, combines the functions of multi-wavelength signal detection and data processing. Herein, the large-scale artificial synaptic device arrays based on the organic molecule-nanowire heterojunctions with tunable photoconductivity are proposed and demonstrated. The organic thin films of p-type 2,7-dioctyl[1]benzothieno[3,2-b][1] benzothiophene (C8-BTBT) or n-type phenyl-C61-butyric acid methyl ester (PC61BM) are used to wrap the InGaAs nanowire parallel arrays to configure two different type-I heterojunctions, respectively. Due to the difference in carrier injection, persistent negative photoconductivity (NPC) or positive photoconductivity (PPC) are achieved in these heterojunctions. The irradiation with different wavelengths (solar-blind to visible ranges) can stimulate the heterojunction devices, effectively mimicking the synaptic behaviors with two different photoconductivities. The long-term and multi-state light memory are also realized through synergistic photoelectric modulation. Notably, the arrays with different photoconductivities are adopted to build the hardware kernel for the visual system. Due to the tunable photoconductivity and response to multiple wavelengths, the recognition rate of neural networks can reach 100% with lower complexity and power consumption. Evidently, these photosynaptic devices are illustrated with retina-like behaviors and capabilities for large-area integration, which reveals their promising potential for artificial visual systems. 相似文献
70.
Anne-Kathrin Knuth Arnaud Huard Zumer Naeem Peter Rappl Rebekka Bauer Ana Carolina Mota Tobias Schmid Ingrid Fleming Bernhard Brüne Simone Fulda Andreas Weigert 《International journal of molecular sciences》2021,22(5)
The interaction of macrophages with apoptotic cells is required for efficient resolution of inflammation. While apoptotic cell removal prevents inflammation due to secondary necrosis, it also alters the macrophage phenotype to hinder further inflammatory reactions. The interaction between apoptotic cells and macrophages is often studied by chemical or biological induction of apoptosis, which may introduce artifacts by affecting the macrophages as well and/or triggering unrelated signaling pathways. Here, we set up a pure cell death system in which NIH 3T3 cells expressing dimerizable Caspase-8 were co-cultured with peritoneal macrophages in a transwell system. Phenotype changes in macrophages induced by apoptotic cells were evaluated by RNA sequencing, which revealed an unexpectedly dominant impact on macrophage proliferation. This was confirmed in functional assays with primary peritoneal macrophages and IC-21 macrophages. Moreover, inhibition of apoptosis during Zymosan-induced peritonitis in mice decreased mRNA levels of cell cycle mediators in peritoneal macrophages. Proliferation of macrophages in response to apoptotic cells may be important to increase macrophage numbers in order to allow efficient clearance and resolution of inflammation. 相似文献