A High Efficiency Wavelength Conversion Scheme Based on Four Wave Minxing in a Semiconductor Optical Amplifier

A new approach of all optical wavelength converter based on four wave mixing (FWM) in a semiconductor optical amplifier (SOA) with the conjugate wave reflected by a fiber Bragg grating (FBG) and then amplified by the SOA is reported. By adjusting the pump power, the conversion efficiency could be improved 7～10dB with signal-to-background-noise-ratio (SBR) deteriorated 1～2dB, compared with traditional single pump four wave mixing.     

Mitochondrial class II introns encode proteins related to the reverse transcriptases of retroviruses

Organelle introns share several distinctive features that set them apart from their counterparts in nuclear-encoded pre-messenger RNAs (reviewed in ref. 1): their termini do not obey the GU...AG rule; the introns are 'structured' (members of the same family or 'class' can theoretically adopt very similar RNA secondary conformations and several of the postulated pairings have been confirmed by studies of splicing mutants and their revertants (see, for example, ref. 4); many introns from both classes contain long open reading frames. We report here that the proteins potentially encoded by four class II introns are related to several RNA-dependent polymerases of viral and transposable element origins.     

热动力学的研究(Ⅶ)——再论一级反应的热动力学研究法

导出了一级反应热谱曲线的t时峰高与t前峰面积之间的关系,以及一级反应速度常数、量热计冷却常数和总峰面积以无量纲参数为变量的数学表达式.还建立了用曲线拟合法求无量纲参数的方法.用这种方法研究了已知反应速度常数的三个反应体系.     

关于干电池内阻测量方法的研究

过去人们通常把干电池的内阻看成是一个恒量,但通过实验证明它是随电流大小而变化的量,所以过去测量干电池内阻的方法必须进行改进。本文对此进行了一些探索,其结果比较精确,符合实际。     

PAN负载聚氨酯泡沫塑料富集分光光度法测定微量锰

报导用PAN螯合剂负载的聚氨酯泡沫塑料富集,分光光度法测定微量锰的简单易行方法。2吡啶偶氮—萘酚(PAN)在pH=9.5缓冲溶液中既做为负载剂又做为显色剂。锰离子富集之后,用1mol/L HNO_3洗脱,光度法测定。在0～0.12Mg/1ml锰离子范围符合比尔定律,方法用于麦饭石水和天然水中微量锰离子测定。     

粉末冶金法合成Gd-Sn-Te体系合金

用粉末冶金方法合成了系列Gd-Sn-Te体系合金,并利用X射线衍射仪和差热分析仪分析试样的相组成和相变.结果表明,该工艺制备的试样成分和组织均匀,元素Gd可以比较均匀地固溶到合金体系中,达到了所需的平衡态.此制备方法满足相图和相结构研究的要求.     

Near-optimal cumulative longitude low-thrust orbit transfer

The indirect method for the continuous low-thrust near minimum cumulative longitude orbit transfer problem is addressed. The movement of the satellite is described by the Gauss equation using the modified equinoctial elements and replacing time as the system independent variable by the cumulative longitude. The maximum principle is adapted to design the optimal control in order to minimize the final cumulative longitude, and the twopoint- boundary-value problem is derived from the orbit transfer problem. The single shooting method is applied in a numerical experiment, and the simulations demonstrate that the orbit transfer mission is fulfilled and the product of the maximal thrust and the minimum cumulative longitude is near constant.     

高纯元素合成磺化汞及其单晶的生长

研究了“真空冷指升华法”制备高纯碘（I2）；采用“三温区汽相合成法”将高纯汞（Hg)与高纯碘合成碘化汞（HgI2);α-HgI2单晶的“三温区定点成核法”的汽相生长，分析讨论了温度场对晶体生长的影响，实验结果表明：汞与碘合成时对碘源区，汞源区，碘化汞沉积区分别设置成不同的合适温度，在合成时碘的量比按化学配比的计算值过量5％左右，且在长晶时对原料进行碘处理的方法能确保HgI2的纯度及汞与碘的最佳化学比，长晶时源区温度在125－126℃，长晶区温度在111－112℃，源区与长晶区的温度梯度为1℃/cm，这样在生工安瓿中所形成的温度场对晶体的生长是比较适宜的。     

Reflective State pattern with dynamic constructiveness

After discussing the reflective method of structure and behavior in the State design pattern based on Role Object pattern and the Reflective pattern of software architecture, this paper proposes a reflective state pattern with dynamic constructiveness. This paper explains the meta level and the base level, which are two levels of this pattern, and specifies the relation of two levels by using Meta Object Protocol (MOP). Then it discusses mechanism of interception and reification for reflecting base, object from Meta object. Finally this paper gives an example of network server for applying the Reflective State pattern.     

英语专业八级考试人文知识题评析

本文从信度、效度及反拨效应等几个方面对2005—2009年英语专业八级考试新增人文知识实考试题进行了简要评析，希望对提高英语专业八级考试人文知识试题的质量有一定的实际价值，以及对考试相关人员有一定的启示。