欧盟对熏剂产品制定最大残留限制标准

最近欧盟委员会对用于采收后的熏剂产品进行了列表登记，这些熏剂将不再受欧盟新的最大残留限制标准的约束。该表属于新的欧盟农药最大残留限制标准管理规则396／2005的附录VII的一部分，旨在帮助那些在收割采收后使用了熏剂产品的农产品免遭贸易损害。     

山区高速公路环境影响评价及对策

根据山区环境和地形特征，论述了山区高速公路的工程特点和环境影响的主要问题，分析了建设期和营运期的环境影响因素，提出了相应的环境保护对策及管理措施。     

风险指引型管理方法及在大亚湾核电厂运行安全管理中的应用

安全评价是核电厂运行安全管理中重要的工作内容。本文运用以概率论为基础的概率风险评价方法(PSA)，在分析核电厂安全评价工作特点的基础上．介绍运用PSA方法进行核电厂安全评价的一般过程与方法．最后结合大亚湾核电厂应用PSA进行设备检修的实例，说明其具有可操作性与科学性。     

读友信箱

耳机的基本知识及选购 Q市面上耳机那么多,它们都有什么不同,又该如何选购呢?另外,好些耳机标称的低频下限都在20Hz以下,真有这么低?     

Experimental Research on Erbium-doped Superfluorescent Fiber Source

The effects of the variations in fiber length, fiber mirror reflectance on efficiency and output power are experimentally investigated for erbium-doped double pass backward superfluorescent fiber sources (SFSs). The influence of fiber length on mean wavelength stability (MWS) has also been demonstrated. By incorporating a short section of un-pumped erbium-doped fiber (EDF) at the output port, the pump power dependent on MWS becomes independent of pumped EDF length. This is a novel phenomenon that hasn‘t been reported up to now,and should be helpful to SFS fabrication and theory analysis. By using a fiber Michelson interferometer as spectrum slicing component,a multi-wavelength fiber source (MWFS) with ～20 channels (from 1542nm to 1559nm) is got. The MWFS has a channel spacing of ～0. 8 nm which satisfies ITUstandard. The intensity fluctuation among channels is less than 0.5dB,and the extinction ratio of all channels is above 14dB. This kind of MWFS should be useful to wavelength division multiplexing systems.