蜂窝基站测试中的射频信号取样

从系统角度出发,主要讨论蜂窝基站测试的射频信号的取样问题.根据国标中的相关要求,通过实验比较讨论衰减器和耦合器的非线性特性,从理论和实验结果进行分析并得出结论.     

Surface‐Enhanced Raman Scattering Using Microstructured Optical Fiber Substrates

Microstructured optical fibers (MOFs) represent a promising platform technology for fully integrated next generation surface enhanced Raman scattering (SERS) sensors and plasmonic devices. In this paper we demonstrate silver nanoparticle substrates for SERS detection within MOF templates with exceptional temporal and mechanical stability, using organometallic precursors and a high‐pressure chemical deposition technique. These 3D substrates offer significant benefits over conventional planar detection geometries, with the long electromagnetic interaction lengths of the optical guided fiber modes exciting multiple plasmon resonances along the fiber. The large Raman response detected when analyte molecules are infiltrated within the structures can be directly related to the deposition profile of the nanoparticles within the MOFs via electrical characterization.     

Encapsulation of Nanoparticles Using Nitrilotriacetic Acid End‐Functionalized Polystyrenes and Their Application for the Separation of Proteins

The use of nitrilotriacetic acid end‐functionalized polystyrenes (NTA‐PS) as a multifunctional nanocarrier for the aqueous dispersion of CdSe, γ‐Fe₂O₃ and gold nanoparticles (NPs) is described. When the amphiphilic end‐ functionalized polystyrenes and NPs are dissolved together in tetrahydrofuran, the addition of water causes the spontaneous formation of micellar aggregates, resulting in the successful encapsulation and aqueous dispersion of NPs. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, and vibrating sample magnetometer (VSM) are used to characterize the structure and properties of the NPs‐containing micellar aggregates (nanocarrier). After complexation of Ni²⁺ with NTA on the surface of the nanocarrier containing γ‐Fe₂O₃, specific binding between Ni‐NTA complex and histidine‐tagged (His‐tagged) proteins enables selective separation of His‐tagged proteins using a magnet.     

Ideal Energy‐Level Alignment at the ZnO/P3HT Photovoltaic Interface

Hybrid semiconductor‐polymer nanostructured solar cells hold the promise of photovoltaic energy conversion based on abundant and nontoxic materials and scalable manufacturing processes. After a decade of intense research activity, hybrid solar cells still exhibit low short‐circuit currents and moderate open‐circuit voltages. These bottlenecks call for a detailed understanding of the physics underlying the device operation at the nanoscale. Using first‐principles calculations the ideal energy‐level alignment of hybrid solar cell interfaces based on the wide bandgap semiconductor ZnO and the polymer poly(3‐hexylthiophene) (P3HT) is investigated. The interfacial charge transfer is quantified and it is shown that this effect increases the ideal open‐circuit voltage with respect to the electron‐affinity rule by as much as 0.5 V. The results of this work suggests that there is significant room for optimizing this class of excitonic solar cells by tailoring the semiconductor/polymer interface at the nanoscale.     

Cold isostatic pressing technique for producing highly efficient flexible dye‐sensitised solar cells on plastic substrates

One of the biggest challenges for making dye‐sensitised solar cells (DSCs) on plastic substrates is the difficulty in making good quality nanoporous TiO₂ films with both good mechanical stability and high electrical conductivity. Cold isostatic pressing (CIP) is a powder compaction technique that applies an isostatic pressure to a powder sample in all directions. It is particularly suitable for making thin films on plastic substrates, including non‐flat surfaces. Cold isostatically pressed nanocrystalline TiO₂ electrodes with excellent mechanical robustness were prepared on indium tin oxide (ITO)‐coated polyethylene naphthalate (PEN) substrates in the absence of organic binders and without heat treatment. The morphology and the physical properties of the TiO₂ films prepared by the CIP method were found to be very compatible with requirements for flexible DSCs on plastics. This room‐temperature processing technique has led to an important technical breakthrough in producing high efficiency flexible DSCs. Devices fabricated on ITO/PEN films by this method using standard P‐25 TiO₂ films with a Ru‐complex sensitiser yielded a maximum incident photon‐to‐current conversion efficiency of 72% at the wavelength of 530 nm and showed high conversion efficiencies of 6.3% and 7.4% for incident light intensities of 100 and 15 mW cm⁻², respectively, which are the highest power conversion efficiencies achieved so far for any DSC on a polymer substrate using the widely used, commercially available P‐25 TiO₂ powder. Copyright © 2011 John Wiley & Sons, Ltd.     

上海光源剂量联锁PLC系统和故障记录

上海光源恒流注入模式需建立辐射剂量硬件联锁。剂量联锁系统以PLC为基础,采用一主站四从站的现场总线布局,通过语句表编程实现逻辑综合,并具有故障记录功能。程序采用字逻辑将状态输入与设定屏蔽位图进行比较,逐个模块地检查有无累积剂量超限输入和瞬时剂量超限输入,综合后经断开延时形成累积剂量联锁输出和瞬时剂量联锁输出。程序通过双字逻辑比较,得到新近发生的故障位置和故障时间,形成故障记录。故障记录功能有助于参与联锁探测器的故障定点诊断和维护。     

氘核中子反应截面的法捷耶夫方程理论计算

中子引起的轻核反应是核数据研究的重要内容。当前我国核数据库中氘核中子反应截面的计算结果局限于采用s 波可分离势,且入射能量在20 MeV以下。需要发展三体核反应的法捷耶夫方程理论方法,采用超出s 波的核子 核子相互作用,从而对更高能量范围内氘核全套中子反应截面做出准确的描述。本文介绍了利用法捷耶夫方程计算n+d三核子反应体系的弹性散射微分截面、破裂反应、破裂反应出射中子和质子的双微分截面的理论框架及数值计算结果,同时计算了弹性散射总截面和破裂反应总截面的激发函数。计算结果与实验数据及CENDL 32、ENDF/B Ⅷ.0、JENDL 5、JEFF 33等数据库中的评价数据符合较好。     

碳化硅结势垒肖特基二极管的质子辐射效应

碳化硅结势垒肖特基二极管(SiC JBS)是新一代航天器电推进系统的关键部件,但高能粒子辐射严重威胁其可靠性与稳定性。为揭示其辐射损伤机理,为其抗辐射加固设计与考核评估储备数据,本研究基于加速器开展了先进商用SiC JBS 10~20 MeV中能质子地面辐照实验,并提取器件辐照前后的正向伏安特性、反向伏安特性、电容电压等电学参数及缺陷特性。系统分析器件关键特性随辐照条件的改变规律。结果显示,质子辐照引起了器件肖特基势垒升高、载流子浓度降低,且10 MeV较低能质子导致的位移损伤退化更严重。分析认为,PN结界面缺陷导致高性能商用SiC JBS反向电学性能对中能质子的辐照更加敏感,正向特性相对稳定,辐照生碳缺陷造成载流子去除效应是引起SiC JBS性能退化的主要机制。     

小剂量辐射影响B16黑色素瘤血道肺转移作用机制研究

Ｃ５７ＢＬ／６小鼠经７．５ｃＧｙＸ线全身照射后２４ｈ静脉注射＾１２５ＩＵｄＲ标记的Ｂ１６黑色素瘤细胞，２４ｈ后测定肺活瘤细胞存留率时发现，照射组小鼠的肺活瘤细胞存瘤率明显降低。与此同时，于照射后２４ｈ检测小鼠的免疫功能发现，照射组小鼠脾脏有核细胞数明显增多，脾细胞ＮＫ细胞毒活性及体内巨噬细胞功能均显著增强，结果提示，小剂量辐射可能通过提高ＮＫ细胞，巨噬细胞功能而加速肺内瘤细胞的清除速率。