一种高灵敏度TD-LTE 通信接收机设计

TD-LTE接入方式、可变大带宽等新技术的运用,对测试仪表接收端性能提出了很高的要求,特别是如何在大带宽下提高接收灵敏度成为设计重点和难点。基于本振馈通抵消技术,设计了一种高灵敏度TD-LTE通信接收机,降低了本振信号馈通,避免了本振馈通引起的杂散、噪声等问题,从而提升了接收机的灵敏度和动态范围。对接收机的测试和理论对比表明,该接收机具有结构简单、易仿真、高指标等特点,可以推广到各种通信制式的测试设备、基站等产品中,具有广泛应用前景。     

高精度的来波方位估计

给出了干涉仪测向的基本原理和数学模型,对干涉仪测向的精度进行了一般性讨论。指出提高测向精度的有效途径是增加基线长度。主要研究长短基线组合方式、测向算法及系统性能分析,重点在于克服测向系统的测向模糊性和提高测向精度。给出了理论上的高精度干涉仪测向算法如何在实际工程中的应用及系统的实现方法以及部分实验数据。     

Overcoming the poor short wavelength spectral response of CdS/CdTe photovoltaic modules via luminescence down‐shifting: ray‐tracing simulations

The short‐wavelength response of cadmium sulfide/cadmium telluride (CdS/CdTe) photovoltaic (PV) modules can be improved by the application of a luminescent down‐shifting (LDS) layer to the PV module. The LDS layer contains a mixture of fluorescent organic dyes that are able to absorb short‐wavelength light of λ < 540 nm, for which the PV module exhibited low external quantum efficiency (EQE), and re‐emit it at a longer wavelength (λ > 540 nm), where the solar cell EQE is high. Ray‐tracing simulations indicate that a mixed LDS layer containing three dyes could lead to an increase in the short‐circuit current density from J_sc = 19.8 mA/cm² to J_sc = 22.9 mA/cm² for a CdS/CdTe PV module. This corresponds to an increase in conversion efficiency from 9.6% to 11.2%. This indicates that a relative increase in the performance of a production CdS/CdTe PV module of nearly 17% can be expected via the application of LDS layers, possibly without any making any alterations to the solar cell itself. Copyright © 2006 John Wiley & Sons, Ltd.     

Transforming One‐Dimensional Nanowalls to Long‐Range Ordered Two‐Dimensional Nanowaves: Exploiting Buckling Instability and Nanofibers Effect in Holographic Lithography

Two‐dimensional nanowaves with long‐range order are fabricated by exploiting swelling‐induced buckling of one‐dimensional (1D) nanowalls with nanofibers formed in‐between during holographic lithography of the negative‐tone photoresist SU‐8. The 1D film goes through a constrained swelling in the development stage, and becomes buckled above the critical threshold. The degree of lateral undulation can be controlled by tuning the pattern aspect ratio (height/width) and exposure dosage. At a high aspect ratio (e.g., 6) and a high exposure dosage, nanofibers (30–50 nm in diameter) are formed between the nanowalls as a result of overlapping of low crosslinking density regions. By comparing experimental results with finite‐element analysis, the buckling mechanism is investigated, which confirms that the nanofibers prevent the deformed nanowalls from recovery to their original state, thus, leading to long‐range ordered two‐dimensional (2D) wavy structures. The film with nanowaves show weaker reflecting color under an ambient light and lower transmittance compared to the straight nanowalls. Using double exposure through a photomask, patterns consisting of both nanowaves and nanowalls for optical display are created.     

A highly luminescent organic crystal with the well-balanced charge transport property: The role of cyano-substitution in the terminal phenyl unit of distyrylbenzene

1,4-bis(2-cyano styryl)benzene (2-CSB) crystal with cyano substituent groups introduced to the terminal phenyl rings of distyrylbenzene (DSB) has been prepared and its luminescence efficiency could be as high as ∼55%. Based on the analyses of cyclic voltammetry and crystal structure, cyano substituents not only lower the LUMO level but also result in a change of the packing mode from the herringbone arrangement to the face-to-face slipped π stacking motif. Then field-effect transistors (FETs) based on high-quality 2-CSB crystals grown by the physical vapor transport method have been fabricated and the highest hole and electron mobilities were measured as 0.66 and 0.29 cm²/Vs, which enhanced the corresponding values of DSB crystal by up to one and two orders of magnitude, respectively. 2-CSB crystal simultaneously combined the high luminescence and the well-balanced mobility is expected to be of interest for the fundamental research of organic light-emitting devices.     

二分量BEC原子数密度在射频场作用下的崩塌与复苏现象

研究射频场频率对二分量玻色-爱因斯坦凝聚体(BEC)原子数密度长时间演化特性的影响,研究结果显示当射频场频率较小而时间较长时BEC第二分量原子数密度的演化呈现出量子力学中典型的崩塌与复苏现象;原子数密度在更长时间的动力学行为中,若射频场频率增大,则呈现出崩塌与复苏现象的原子数密度震荡曲线整体逐渐下降.     

ZnO薄膜材料的发光特性

回顾了最近几年对 Zn O薄膜材料发光特性的研究进展 ,介绍了用不同方法制备 Zn O薄膜的自发辐射和受激辐射发光特性。     

Harvesting Lost Photons: Plasmon and Upconversion Enhanced Broadband Photocatalytic Activity in Core@Shell Microspheres Based on Lanthanide‐Doped NaYF4, TiO2, and Au

Efficiently harvesting solar energy for photocatalysis remains very challenging. Rational design of architectures by combining nanocomponents of radically different properties, for example, plasmonic, upconversion, and photocatalytic properties, offers a promising route to improve solar energy utilization. Herein, the synthesis of novel, plasmonic Au nanoparticle decorated NaYF₄:Yb³⁺, Er³⁺, Tm³⁺‐core@porous‐TiO₂‐shell microspheres is reported. They exhibit high surface area, good stability, broadband absorption from ultraviolet to near infrared, and excellent photocatalytic activity, significantly better than the benchmark P25 TiO₂. The enhanced activity is attributed to synergistic effects from nanocomponents arranged into the nanostructured architecture in such a way that favors the efficient charge/energy transfer among nanocomponents and largely reduced charge recombination. Optical and energy‐transfer properties are modeled theoretically to support our interpretations of catalytic mechanisms. In addition to yielding novel materials and interesting properties, the current work provides physical insights that can contribute to the future development of plasmon‐enhanced broadband catalysts.     

A Chlorotoxin-Directed Diselenide-Bridged Tumor-Homing Persistent Luminescence Nanoprobes Mediating Inhibition of Oxidative Phosphorylation for Long-Term Near-Infrared Imaging and Therapy of Glioblastoma

Glioblastoma (GBM) is the most prevailing malignant primary brain tumor, and the precise diagnosis of GBM has always been a challenge. Gboxin is a recently developed drug efficiently inhibiting the oxidative phosphorylation in GBM cells, and both the chlorotoxin (CLTX) and GBM cell membrane coating are capable of GBM targeting and tumor homing. Herein, the near-infrared (NIR) persistent luminescence (PL) nanoparticle, CUDZG, with a dual function of imaging and therapy is developed based on ZnGa₂O₄:Cr³⁺,Sn⁴⁺. CUDZG exhibits superior rechargeable NIR PL for at least 48 h with excellent tissue penetration in vivo, which enables the longstanding autofluorescence-free imaging of the orthotopic GBM. The tumor growth of both the orthotropic and subcutaneous GBM-bearing mice are significantly suppressed by CUDZG. This is the first-time report of 1) the integration of CLTX and cell membrane coating for drug delivery, 2) diselenide-based trigger release for anti-GBM therapy, and 3) the systemic delivery of Gboxin. This study also offers an example of the highly promising blood-brain penetrable drug carriers for precise diagnosis and therapy of central nervous system diseases.     

同时测量弯曲曲率和弯曲方向的长周期光纤光栅传感器

通过实验发现了高频CO2激光脉冲制备的长周期光纤光栅（LPFGs）的弯曲特性具有明显的弯曲方向性：即当其向不同的方向弯曲时,其谐振波长和损耗峰值的变化对应的弯曲灵敏度不同,并且在两个弯曲方向上最敏感,而在另外两个弯曲方向最不敏感。本文根据此独特性质,提出了不仅可以测量弯曲曲率而且可以同时判别弯曲方向的传感器,该弯曲传感器由2个具有弯曲方向相关性的LPFG和1个没有弯曲方向相关性的LPFG组成。结果表明,它克服了其它弯曲传感器只能测量弯曲曲率或只能判别弯曲方向的缺点。