Strategies to Improve Field Emission Performance of Nanostructural ZnO

Nanostructural ZnO is a good candidate for field emission (FE) because of its high aspect ratio, controllable electrical conductivity, and good thermal and chemical stability. In order to improve the FE performance, ZnO nanopins, gallium-doped nanofibers, periodic nanorod arrays, and aligned nanotubes were designed and fabricated by a vapor-phase transport method using ZnO + C and ZnO + C + Ga₂O₃ powder mixtures, electrochemical deposition, and hydrothermal decomposition, respectively. The FE behaviors including threshold of electric field, emission current density, field enhancement factor, and stability are reviewed in this paper based on our previous works. Some strategies to improve the performance of the nanostructural ZnO field emitters are demonstrated.     

(Semi-)blind channel estimation for space time block coded system with transmit diversity

This paper deals with a blind channel estimation method for space-time coded block transmission system. By concatenating the real part and imaginary part of the received signal to form an elongated vector, we derive an equivalent input–output system model. Then channel state information (CSI) is blindly estimated using subspace method, utilizing only the redundancy inherent in space-time block coding (STBC) and cyclic prefix (CP). The estimation ambiguity, which is common to all blind methods, is analyzed in detail and we prove that there only exist four scalar indeterminacies. Three effective methods to eliminate the ambiguities are also proposed. Compared with other blind channel estimation methods for space time systems, this method needs neither redundant precoding nor oversampling, and thus has higher data rate. Besides, this method is robust to channel order overestimation, which is effectively demonstrated by numerical simulations. This work was supported by NSFC (60496310, 60672093), NSFJS(BK2005061) and BK2005061.     

多径信道PAM-TH-MA系统性能分析

超宽带(UWB)通信具有数据速率高、功率谱密度低、定位精度高以及抗多径能力强等优点,通过重复利用频谱,可解决频谱拥挤不堪的问题,已成为无线通信领域研究的热点。本文针对PAM-TH-MA系统在多径信道下的抗噪性能进行研究,并比较了分别采用S-Rake和P-Rake接收机时的性能。仿真结果表明,采用S-Rake接收机时的系统性能优于P-Rake接收机。     

EMG and EPP-integrated human-machine interface between the paralyzed and rehabilitation exoskeleton

Although a lower extremity exoskeleton shows great prospect in the rehabilitation of the lower limb, it has not yet been widely applied to the clinical rehabilitation of the paralyzed. This is partly caused by insufficient information interactions between the paralyzed and existing exoskeleton that cannot meet the requirements of harmonious control. In this research, a bidirectional human-machine interface including a neurofuzzy controller and an extended physiological proprioception (EPP) feedback system is developed by imitating the biological closed-loop control system of human body. The neurofuzzy controller is built to decode human motion in advance by the fusion of the fuzzy electromyographic signals reflecting human motion intention and the precise proprioception providing joint angular feedback information. It transmits control information from human to exoskeleton, while the EPP feedback system based on haptic stimuli transmits motion information of the exoskeleton back to the human. Joint angle and torque information are transmitted in the form of air pressure to the human body. The real-time bidirectional human-machine interface can help a patient with lower limb paralysis to control the exoskeleton with his/her healthy side and simultaneously perceive motion on the paralyzed side by EPP. The interface rebuilds a closed-loop motion control system for paralyzed patients and realizes harmonious control of the human-machine system.     

Low-Dose X-ray CT Reconstruction via Dictionary Learning

Although diagnostic medical imaging provides enormous benefits in the early detection and accuracy diagnosis of various diseases, there are growing concerns on the potential side effect of radiation induced genetic, cancerous and other diseases. How to reduce radiation dose while maintaining the diagnostic performance is a major challenge in the computed tomography (CT) field. Inspired by the compressive sensing theory, the sparse constraint in terms of total variation (TV) minimization has already led to promising results for low-dose CT reconstruction. Compared to the discrete gradient transform used in the TV method, dictionary learning is proven to be an effective way for sparse representation. On the other hand, it is important to consider the statistical property of projection data in the low-dose CT case. Recently, we have developed a dictionary learning based approach for low-dose X-ray CT. In this paper, we present this method in detail and evaluate it in experiments. In our method, the sparse constraint in terms of a redundant dictionary is incorporated into an objective function in a statistical iterative reconstruction framework. The dictionary can be either predetermined before an image reconstruction task or adaptively defined during the reconstruction process. An alternating minimization scheme is developed to minimize the objective function. Our approach is evaluated with low-dose X-ray projections collected in animal and human CT studies, and the improvement associated with dictionary learning is quantified relative to filtered backprojection and TV-based reconstructions. The results show that the proposed approach might produce better images with lower noise and more detailed structural features in our selected cases. However, there is no proof that this is true for all kinds of structures.     

个性化推荐在移动互联网业务中的应用

以SoLoMo为标志的新一轮商业模式带动了移动互联网时代用户的上网行为及消费方式的转变,用户对互动性、实时性服务的需求愈发迫切,服务差异化和需求个性化的期望也为数据挖掘和应用提供了新的机遇和挑战。本文从移动互联网用户的行为知识库开放平台、智能化用户模型关键技术、个性化信息推荐及应用等几个方面,探索如何构造一个共赢的移动生态产业链体系。     

Multi-Functional Black Bioactive Glasses Prepared via Containerless Melting Process for Tumor Therapy and Tissue Regeneration

Tissue regeneration in complex lesions such as the site of tumors, bacterial infection, and sites lacking blood vessels, has been a huge challenge. Therefore, developing bioactive implantable materials with multi-functional properties such as tumor destruction, bacteria growth inhibition, and angiogenesis promotion is of great significance. In this study, black CaO-SiO₂-TiO₂ (CST) glasses are prepared through the containerless melting approach, by which heterogeneous nucleation can be avoided and thereby glass formation becomes possible via fast quenching. This approach enables the formation of trivalent titanium (Ti³⁺) without using a reducing atmosphere or reducing agents. The black CST glasses are found in this study to possess a strong ability to inhibit bacteria and tumors by their excellent photothermal and photocatalytic effects. Strikingly, these glasses also promote the formation of blood vessels and accelerate the healing of chronic wounds by the synergistic effects of the photothermal effect and Si ions. Thus, this glass system can be a promising multi-functional material for tissue regeneration in complex lesions.     

A Bionanozyme with Ultrahigh Activity Enables Spatiotemporally Controlled Reactive Oxygen Species Generation for Cancer Therapy

Nanozymes hold great potential in nanomedicine, yet biotoxicity limits their clinical translation because of their uncontrolled catalytic activity, artificial inorganic components, and harsh synthesis conditions. Herein, a peroxidase-like bionanozyme with ultrahigh and photocontrolled catalytic activity through the self-assembly of biomolecules, hemin, and in situ polymerization of pyrrole in an aqueous solution is reported. Such bionanozymes leverage the specific cues of the tumor microenvironment and precise light-induced photothermal heating for spatiotemporally controlled reactive oxygen species generation in tumors. The tunable catalytic activity and excellent biocompatibility of the bionanozyme result in high cancer cell apoptosis and tumor growth inhibition in murine models with negligible biotoxicity. This work highlights the potential of biomolecule-based nanozymes for cancer-specific therapy. Bionanozymes with ultrahigh and tunable catalytic activity may lay the important foundation for more advanced nanomedicine and biosensing.     

A High Capacity All Solid-State Li-Sulfur Battery Enabled by Conversion-Intercalation Hybrid Cathode Architecture

As demands for electrochemical energy storage continue to rise, alternative electrochemistries to conventional Li-ion batteries become more appealing. Here, an intercalation-conversion hybrid cathode that combines intercalation-type VS₂ with conversion-type sulfur chemistry to construct high performance solid-state lithium-sulfur batteries is reported. The layered VS₂ nanomaterial features Li-ion transport channels, metallic conductivity, and active capacity contribution, all of which provide an ideal platform for the solid state S/Li₂S redox couple to unlock its high gravimetric capacity. The S/VS₂/Li₃PS₄ hybrid cathode composite is prepared by a facile, low-cost, and low-energy mechanical blending process. The S/VS₂/Li₃PS₄|Li₃PS₄|Li/In (or Li) all-solid-state cell exhibits sulfur utilization of ≈85%, with a Coulombic efficiency of close to 100%. High areal capacity up to 7.8 mA h cm⁻² with an active material loading (S/VS₂) as high as 15.5 mg cm⁻² is achieved.