1、注意標題上邊有一空行平頂山學院2010屆本科生畢業論文小五號宋體/ Times New Roman四號黑體，加粗，居中，段前）-行，段后1行。_譜儀系統百分死時間與計數率丟失校正因子的關系，使該系統允許計數率大大提高，王某某HPGe 丫譜儀系統死時間校正方法的實驗研究小二號黑體，加粗，居中，段前1.5行，段后1.5行給出了 HPGe y譜儀系統死時間校正的一種實用方法。用強源干擾找到了 HPGe y四號字，Arial Black，居中， 段前0行，段后1行。AbstractKey Words： HPGey spectrometer, Deadtime, Coefficient of corre

2、ction小四號字，ArialBlack小四號字，Times、New Roman小四號字，Times New Roman，1.5 倍行距（如果內容較多可適當減速 小行距，以美觀為標準）英文狀態下的逗號，且后有一空格Experimental study on the method of deadtimecorrection For HPGe yspectrometer system小三號字，Arial Black，居中，段前1.5 行，段后1.5行。標題兩行間距30磅A practical method of deadtime correction for HPGe y spectrometer

3、 system was given.The relationbetween the percent deadtime and the correction of counting rate losses for HPGe y spectrometer system was found by using a strong y source. Therefore ,the activity measurement can be finished at very high count rate,with this y spectrometer.注意：如果摘要內容較多，一頁排不下，則中文摘要（含關鍵詞

4、）單獨占一頁，英 文摘要（含關鍵詞）單獨占一頁。如下所示：a -取代甲苯定向硝化的理論研究運用密度泛函理論(DFT),研究了吸電子氟基和供電子羥基在取代甲苯的a-H以 后，其鄰、間、對各位次進行硝化反應的速控步驟,在B3LYP/6-311G*水平上,計算 了該速控步驟基元反應各反應駐點(反應物、過渡態和中間體)的優化幾何、電子結構 和能量性質，并首次給出了目標硝化反應速控步驟的IR譜學的動態特征及解析，從 微觀層面上驗證了反應坐標C-N的形成和C-H的斷裂是非協同的，從而無一級動力 學同位素效應的實驗事實.通過對目標硝化反應速控步驟的微觀動態計算，驗證了氟 基對甲基定位的影響.氟基的電負性大，

5、吸電子能力強，取代甲苯的a-H以后對 硝酰陽離子的進攻有抑制作用，活化能較取代前高，但比較芐基氟各位次硝化活化能 的相對大小得知，一CH2F仍為鄰、對位定向基團.而供電子羥基取代甲苯的a-H以 后，則對硝酰陽離子的進攻有促進作用，因而各反應駐點絡合物的穩定化能較a-H取 代前甲苯的有所增大，且鄰、對位硝化的活化能較間位低，故一CH2OH為鄰、對位定 位基.但對位因硝化活化能低，反應放熱多，空間位阻小，為親電試劑NO +最有利的 進攻位；而鄰位則因羥基取代甲苯a-H 后多了2 一個氧原子，增大了鄰位進攻的空間位阻，使得其絡合物的能量比相應對位的高.關鍵詞：芐基氟，芐醇，a-取代，取代基效應，速控

6、步驟Theoretical Study on Selectivity for Nitration ofa-Substituted Toluene with NitroniumAbstractThe rate-determining steps of isomeric ortho, meta and para nitrations of benzyl alcohol and benzyl fluoride have been theoretically investigated at B3LYP/6-311G* level. Stationary points of the step invol

7、ving reactant, transition state and intermediate complexes were successfully located and characterized without any restriction on the internal coordinates. Their molecular geometries, electronic structures, IR spectra, and the FMO symmetries of two initial aromatic compounds and the nitronium ion NO

8、 + have been studied. The vibrational shifts of CN and CH stretches from TS to INT at the rate-determining step of target aromatic nitrations show up that the formation of C N and the cleavage of CH are not con-cerned but stepwise to provide an explanation, on a microscopic scale, for the experiment

9、al fact of the absence of kinetic isotopic effect in the nitration process for the first time. Also, the influence of introduced fluorine on the orientation effect was figured by calculating the microscopic and kinetic properties of the rate-determining step of concerned aromatic nitrations. The NO

10、+ attack to the benzyl fluoride was deactivated because of high electronegativity and strong electron withdrawal of fluorine atom. The activation energy af ter a -substitution of methyl group by a fluorine atom became higher. Yet the CH2F group was still an ortho-para directive, since the activation

11、 energies of ortho and para nitrations were relatively lower than that of meta nitration. Contrarily, the introduction of electron-donating substituent OH onto the methyl accelerated the NO + attack. Consequently the stabilization energies of complexes were droped even lower than before the a-substi

12、tution occurred. The activation energies of ortho and para nitrations, however, were also quite lower than the energy of meta nitration. Therefore, the C%OH is an ortho-para directing group. Compared to the ortho, the para position is the most favorable due to the NO + to approach, for its low steric hindrance effect and high exothermicity. Attack at ortho, however, became even more crowd since one more O atom has been introduced after the a-substitution onto the methyl gro