丙二醇甲醇以太结束胺物综合由超音波技术Xuehong张a， b， Wenyu张a， b， Junping李a， Ning赵a，韦・韦a， Yuhan太阳a修改了多孔硅土， *煤炭转换，学院煤炭化学，中国科学院，太原030001，中国b研究生院状态钥匙实验室中国科学院，北京100039，中国接受了2006年5月16日; 接受以修改过的形式2006年7月10日; 接受2006年7月12日
Synthesis of propylene glycol methyl ether over amine modifiedporous silica by ultrasonic techniqueXuehong Zhang a,b, Wenyu Zhang a,b, Junping Li a, Ning Zhao a, Wei Wei a, Yuhan Sun a,*a State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, Chinab Graduate School of the Chinese Academy of Sciences, Beijing 100039, ChinaReceived 16 May 2006; received in revised form 10 July 2006; accepted 12 July 2006Available online 21 July 2006AbstractAmine modified porous silica were synthesized by ultrasonic technique under mild The samples, which were characterizedby BET, 29Si NMR spectra, element analysis and indicator dye adsorption, exhibited promising catalytic properties towards the synthesisof propylene glycol methyl ether from methanol and propylene They had both high yields and reusability in the reaction, indicatingthat ultrasonic technique was effective for the preparation of organically modified silica Furthermore, the possible reactionmechanism was proposed for the synthesis of propylene glycol methyl ether over such type of 2006 Elsevier BV All rights Keywords: Modified porous silica; Ultrasonic technique; Propylene oxide; Methanol; Propylene glycol methyl IntroductionThe attempt to heterogenize homogeneous catalyst asalternatives to more traditional reagents and catalysts hasbeen one area of research that has seen increasing Much recent work was focused on the preparation oforganically modified solid bases to heterogenize homogeneousamine The modification process was generallyoperated by stirring, heating, refluxing, [1–3]Recently, the interest in synthetic sonochemistry reactionshas grown [4] The ultrasonic technique has been widelyapplied in two-phase systems due to its advantages, suchas high accuracy and Most of these reactions haveinvolved a heterogeneous chemical interaction [5] In thearea of porous materials functionalized by organic groups,however, only limited applications of ultrasound have beenexplored [6,7] In the present work, an alternative syntheticroute for the formation of amine modified silica was developedby using ultrasonic energy, which can produce chemicalmodifications on solids by cavitation phenomenon [8]The amines modified silica with ‘‘single site’’ base strengthwere promising catalysts for a variety of reactions [9]The synthesis of glycol ether over base catalysts is animportant kind of reaction in organic There areseveral methods for the synthesis of propylene glycol ether[10,11] Among them the propylene oxide method is mostlyconvenient and industrial Generally, propyleneoxide reacts with fatty alcohol via acid or base The catalysts used in this process include earlier homogenousbase or acid (NaOH, alcoholic sodium and BF3), latersolid acid and However, few studies have reported theuse of amine modified silica as catalysts for the synthesis ofpropylene glycol methyl ether, though inorganic solid basiccatalysts have performed good activity in the Theimmobilization of the amino functions on a mesoporoussupport, which were with ‘‘single site’’ base strength, couldafford an achieving this kind of In the present work, amine functionalized silica catalysts,including NH2/SiO2, NH(CH2)2NH2/SiO2, TAPM/SiO2 (2,4,6-triaminopyrimidine/SiO2) and TBD/SiO2(1,5,7-triazabicyclo[4,4,0]dec-5-ene/SiO2), were preparedwith 3-aminopropyltrimethoxysilane (APTMS), N-[3-(tri-methoxysilyl)propyl]ethylenediamine (EDPTMS) and 3-chloropropyltrimethoxysilane (CPTMS) as the couplingagents by ultrasonic technique under mild At the same time, in order to confirm the meritsof ultrasonic technique, NH2/SiO2 was also prepared bythe conventional method in order to understand the effectivebehaviour of ultrasonic technique in the preparationof functionalized porous In addition, the catalyticactivity of the organic solid base catalysts was evaluatedby the synthesis of propylene glycol methyl ether frommethanol and propylene Furthermore, the possiblereaction mechanism was proposed for the synthesis of propyleneglycol methyl ether over such type of E Synthesis of catalytic materialsThe amine functionalized silica catalysts could beachieved in two ways under similar conditions as reportedearlier [7]Aminopropylsilyl-functionalized SiO2 was prepared asfollows: 0 g SiO2 was preheated for 12 h at 473 K invacuum to remove all adsorbed moisture but surfaceOH-groups, and than cooled down to room temperaturein vacuum and transferred into a 250 mL conical After mixed with 0 mL cyclohexane and 0 mLAPTMS, the mixture in conical flask was put into the ultrasonicbath for 2 h (Sheshin, Japan, operating power 60 W)at ambient The catalyst was then obtained byextracting with toluene in a soxhlet extractor over a periodof 24 h and drying at 333 K in The same methodwas used for the preparation of NH(CH2)2NH2/SiOTBD/SiO2 was prepared by two steps: silica was firstlymodified by 3-chloropropyltrimethoxysilane via the samemethod as that of aminopropylsilyl-functionalized SiO2,and chloropropylsilyl-functionalized SiO2 was then reactedwith TBD (0 g) in cyclohexane (0 mL) The resultantwas treated by ultrasonic vibration for 1 Afterwards,the catalyst was obtained by extracting with toluene in aSoxhlet extractor over a period of 24 h and drying at333 K in The same method was used for the preparationof TAPM/SiO CharacterizationThe content of carbon, nitrogen, and hydrogen in all thesamples was determined using a Vario EL Thespecific surface area, total pore volume and average porediameter were measured by N2 adsorption–desorptionmethod on a Micromeritics ASAP-2000 instrument (Norcross,GA) The surface areas were calculated by BETmethod, and the pore size distribution was obtained byapplying the BJH pore analysis to the nitrogen adsorption–desorption 29Si NMR spectra were recordedon a Bruker MSL-400 The base strength ofsamples was detected by hammett Catalytic testThe catalytic properties were measured in a 75 ml batchreactor with mol ratio of methanol and propylene oxidebeing 5: After running at 403 K for 10 h under magneticstirring, the reactor was cooled down to room The product was then filtered and analyzed by a gas chromatographwith a flame ionization detector after centrifugalseparation from the The catalysts werewashed with solvent and used for recycling Results and Modification of porous silica with amine groupsThe content of carbon, nitrogen, and hydrogen inamine-free porous silica and all the modified samples werecarried out by elemental W and N% wereobtained from N%, C% and H% (see Table 1) The resultsshowed that there were no carbon and nitrogen in theamine-free porous As a result, carbon and nitrogenin modified samples ought to be from the The element analysis showed that N% of the graftedorganic groups achieved by conventional methods knownfrom the literature [12] was 13 mmol/g, which was farlower than that of the sample prepared by ultrasonic technique(00 mmol/g) (see Table 1) This should be due tothe application of ultrasonic energy to solids and liquids,which could provide the changes including cavitation(bubble formation in a liquid) and chemical reaction (accelerationof chemical reaction), [13] As a result, processesincluding particle size modification, cleaning ofsurfaces or the formation of fresh ones [14,15] could beobtained in heterogeneous media at a solid liquid As to the organic modification of porous silica, cavitationphenomena brought by ultrasound could speed up theliquid transferring velocity in the hole of porous materialsand the liquid–solid As a result, the liquidorganosilanes could be well contacted with silanol groupson the inner wall of the porous silica to react with themin a short time, while stiring could not reach such Therefore, the modification process finished simply andspeedily by The 29Si NMR spectra in solid state indicated that thecovalent bond formed between silylant agents and silanolgroups on the silica surface (see F 1) Two resonancesat 109 and 99 ppm could be attributed to 29Si nucleihaving four Si–O–Si linkages (Q4) and 29Si nuclei havingthree Si–O–Si linkages and one OH (Q3) [16], The resonances at 58 and 67 ppm were assignedto RSi(OSi)(OH)2 and RSi(OSi)3, respectively [17], whichillustrated the successful organo functionalization of poroussilica by the organic groups via covalent C/Nvalue (molar ratio) could also reflect the degree of graftingreaction between silanol groups and organosilanes [18]NH2/SiO2, NH(CH2)2NH2/SiO2 and TBD/SiO2 showedthe C/N = 3–5, 5–0 and 3–6, Theresults also suggested the anchorage of amine groups bySi–O–Si This agreed with the result of the 29SiNMR Structure and basicity of samplesF 2 displays N2 adsorption isotherms for the The functionalized samples displayed type IV isothermswith clear hysteresis loops associated with This indicated that the materials remainedmesoporous before and after functionalization and themodification by various organosilanes hardly changed theisotherm The BET surface area and pore volumeshowed a gradual reduction as the N% of graftedorganic groups increased (see Table 2) This could beattributed to the presence of functional A part ofamino groups grafted onto the microporous also led to adecrease in the BET surface The effect of the organicgroups on the pore diameter of the samples was slight forthe samples NH2/SiO2 and NH(CH2)2NH2/SiO But asfor the sample TBD/SiO2 and TAPM/ SiO2, perhaps dueto the big framework of (CH2)3/TAPM and (CH2)3/TBD groups, the average pore diameters of the samplesdecreased to 90 and 82 However, the average porediameter was not decreased seriously due to the low N%values of the The base strength H of a solid surface is defined as theability of the surface to convert an adsorbed electricallyneutral acid into its conjugate When an electricallyneutral acid indicator is adsorbed on a solid base from anonpolar solution, the color of the acid indicator is changedto that of its conjugate base, provided that the solidhas the necessary base strength to impart electron pairsto the acid [19] A solid with a large positive HH hasstrong basic Grafting with different functional groupscould result in different base As shown in Table3, TBD/SiO2 had the highest base strength of H 0,while NH2/SiO2 and NH(CH2)2NH2/SiO2 only had thebasicity of H 3 and 3 < H < 0, Compared to the other modified samples, TAPM/SiO2had weakest basicity of H < Thus, the basic strengthof the samples was in the order of TBD/SiO2 > NH(CH2)2NH2/SiO2 > NH2/SiO2 > TAPM/SiO Catalytic performanceThe catalytic activity was tested in the synthesis of propyleneglycol methyl ether from methanol and propyleneoxide (see Table 3) As shown in Table 3, PO conversionand isomer selectivity (the ratio of 1-methoxy-2-propanol/total propylene glycol methyl ether) reached 3 3% without the presented catalysts, Amongthe catalysts, the amine-free porous silica showed the lowcatalytic activity due to the weak acid strength of the surfacesilanol For anchored amino groupsNH(CH2)2NH2/SiO2 and NH2/SiO2 catalysts were foundto be more active and selective than other catalysts to 1-methoxy-2-propanol after 10 h of TAPM/SiO2catalyst had low propylene oxide conversion (0%) withthe isomer selectivity of 6% TBD/SiO2,NH(CH2)2NH2/SiO2 and NH2/SiO2 catalysts all showedhigh propylene oxide conversion (>94%), but different NH(CH2)2NH2/SiO2 and NH2/SiO2 withweaker base strength had higher isomer selectivity(>82%), while TBD/SiO2 with moderate base strengthshowed lower isomer selectivity (7%) As for solid basecatalysts, catalysts with moderate base strength shouldhave good isomer selectivity [20] The lower isomer selectivityof TBD/SiO2 could be due to the big framework ofTBDThe catalysts were easily recovered by filtration, andsubjected to utilization for seven cycles with constant conversionof propylene oxide >89% and the utilization formany recycles hardly changed the isomer selectivity under403 K (see Table 4), indicating that amine groups graftedonto silica surface were stable under the experimental The reusability of other samples was similar to thatof NH2/SiO Possible mechanismInorganic solid base catalysts have been extensively usedfor the synthesis of propylene glycol methyl ether frommethanol and propylene oxide [31], in which, the methoxideion and proton was absorbed on acidic and basic siteson the catalyst surface, respectively, and then the methoxideion attacked the C(1) In the present case, however,the samples used for the reaction were characteristicof single site, , the catalyst with unique basic site similarto the homogeneous Because there was no Lewisacidic site on the catalysts, the mechanism should be differentfrom those involving bifunctional The plausiblemechanism of 1-methoxy-2-propanol formation onNH2/SiO2 is illustrated in Scheme There was H-bondsformation between methanol and amine groups in path In path 2, because of the sterically hindered CH3 of PO, theO atom in methanol attacked the C(1) position and protonwas absorbed on the basic sites of the catalysts, and thenC(1)–O band cracked, followed by pick up the proton toform 1-methoxy-2-It seems reasonable to consider that the higher activityof NH(CH2)2NH2/SiO2, NH2/SiO2 and TBD/SiO2 wasdue to the appropriate base strength, which could not onlyform H-bond but also crack it TAPM/SiO2 withvery weak base strength could only form more unstableH- Thus, the activity of TAPM/SiO2 was lower thanthe other On condition that such mechanism isreasonable, the big framework of the organic groups probablycould affect the attacking position of the O atom As a result, TBD of the big framework led tolower isomer Thus, both appropriate basestrength and simple framework of the organic groups wereimportant for the high conversion and good selectivity to1-methoxy-2- ConclusionsThe results presented above led to the following conclusions:(1) the efficient ultrasonic technique could successfullyprepare the amine functionalized porous silicacatalysts, (2) the characterization indicated that the aminegroups were grafted onto the silica surface by covalentbond, (3) appropriate base strength and simple frameworkof the organic groups were important for the high conversionand good selectivity to 1-methoxy-2-propanol, (4) thecatalysts could be recovered by filtration and were subjectedto utilization for many cycles with constant
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各方面计量方法圆钢重量（公斤）=00617×直径×直径×长度 方钢重量（公斤）=00785×边宽×边宽×长度 六角钢重量（公斤）=0068×对边宽×对边宽×长度 八角钢重量（公斤）=0065×对边宽×对边宽×长度 螺纹钢重量（公斤）=00617×计算直径×计算直径×长度 角钢重量（公斤）=00785×（边宽+边宽-边厚）×边厚×长度 扁钢重量（公斤）=00785×厚度×边宽×长度 钢管重量（公斤）=02466×壁厚×（外径-壁厚）×长度 六方体体积的计算 公式① 866×H/m/k 即对边×对边×866×高或厚度 各种钢管(材)重量换算公式 钢管的重量=25×π×(外径平方-内径平方)×L×钢铁比重 其中：π = 14 L=钢管长度 钢铁比重取8 所以， 钢管的重量=25×14×(外径平方-内径平方)×L×8 * 如果尺寸单位取米（M）,则计算的重量结果为公斤（Kg） 钢的密度为： 85g/cm3 （注意：单位换算） 钢材理论重量计算 钢材理论重量计算的计量单位为公斤（ kg ）。其基本公式为： W（重量，kg ）=F(断面积 mm2)×L(长度，m)×ρ(密度，g/cm3)×1/1000 各种钢材理论重量计算公式如下： 名称（单位） 计算公式 符号意义 计算举例 圆钢 盘条（kg/m） W= 006165 ×d×d d = 直径mm 直径100 mm 的圆钢，求每m 重量。每m 重量= 006165 ×1002=65kg 螺纹钢（kg/m） W= 00617 ×d×d d= 断面直径mm 断面直径为12 mm 的螺纹钢，求每m 重量。每m 重量=00617 ×12 2=89kg 方钢（kg/m） W= 00785 ×a ×a a= 边宽mm 边宽20 mm 的方钢，求每m 重量。每m 重量= 00785 ×202=14kg 扁钢 （kg/m） W= 00785 ×b ×d b= 边宽mm d= 厚mm 边宽40 mm ，厚5mm 的扁钢，求每m 重量。每m 重量= 00785 ×40 ×5= 57kg 六角钢 （kg/m） W= 006798 ×s×s s= 对边距离mm 对边距离50 mm 的六角钢，求每m 重量。每m 重量= 006798 ×502=17kg 八角钢 （kg/m） W= 0065 ×s ×s s= 对边距离mm 对边距离80 mm 的八角钢，求每m 重量。每m 重量= 0065 ×802=62kg 等边角钢 （kg/m） = 00785 ×[d （2b – d ）+215 （R2 – 2r 2 ）] b= 边宽 d= 边厚 R= 内弧半径 r= 端弧半径 求20 mm ×4mm 等边角钢的每m 重量。从冶金产品目录中查出4mm ×20 mm 等边角钢的R 为5 ，r 为2 ，则每m 重量= 00785 ×[4 ×（2 ×20 – 4 ）+215 ×（52 – 2 ×2 2 ）]=15kg 不等边角钢 （kg/m） W= 00785 ×[d （B+b – d ）+215 （R2 – 2 r 2 ）] B= 长边宽 b= 短边宽 d= 边厚 R= 内弧半径 r= 端弧半径 求30 mm ×20mm ×4mm 不等边角钢的每m 重量。从冶金产品目录中查出30 ×20 ×4 不等边角钢的R 为5 ，r 为2 ，则每m 重量= 00785 ×[4 ×（30+20 – 4 ）+215 ×（52 – 2 ×2 2 ）]=46kg 常用数据 1 米(m)＝ 281 英尺 1 英寸＝ 4 毫米 1 磅＝ 4536 公斤 1 盎司＝ 3 克 1 公斤力＝ 81 牛顿 1 磅力＝45 牛顿 1 兆帕=161 磅 / 英寸 钢的比重(密度）： 8g/cm 不锈钢比重（密度）：78g/cm 铝的比重（密度）： 7g/cm 锌比重（密度）： 05g/cm 几种金属型材理论重量简易计算公式： 1、 角钢：每米重量=00785×（边宽+边宽—边厚）×边厚 2、 管材：每米重量=02466×壁厚×（外径—壁厚） 3、 圆钢：每m重量=00617×直径×直径 (螺纹钢和圆钢相同） 4、 方钢：每m重量=00786×边宽×边宽 5、 六角钢：每m重量=0068×对边直径×对边直径 6、 八角钢：每m重量=0065×直径×直径 7、 等边角钢：每m重量=边宽×边厚×015 8、 扁钢：每m重量=00785×厚度×宽度 9、 无缝钢管：每m重量=02466×壁厚×(外径-壁厚) 10、电焊钢：每m重量=无缝钢管 11、钢板：每㎡重量=85×厚度 12、黄铜管：每米重量=02670×壁厚×（外径-壁厚） 13、紫铜管：每米重量=02796×壁厚×（外径-壁厚) 14、铝花纹板：每平方米重量=96×厚度 15、有色金属密度：紫铜板9 黄铜板5 锌板2 铅板37 16、有色金属板材的计算公式为：每平方米重量=密度×厚度 17、方管: 每米重量=(边长+边长)×2×厚×00785 18、不等边角钢 ： 每米重量=00785×边厚(长边宽+短边宽--边厚) 19、工字钢 ：每米重量=00785×腰厚[高+f（腿宽-腰厚）] 20、槽钢： 每米重量=00785×腰厚[高+e（腿宽-腰厚）] 备注： 1、角钢、工字钢和槽钢的准确计算公式很繁，表列简式用于计算近似值。 2、f值：一般型号及带a的为34，带b的为65，带c的为26。 3、e值：一般型号及带a的为26，带b的为44，带c的为24。 4、各长度单位均为毫米（mm)
你选一个吧尼古丁 在最初的应用，激怒规定值是signifi- cantly更高(P<001)为尼古丁被对待的边com- 削去与车被对待的边(表1)Initial规定值是 相似为5和1 h interstimulus间隔时间适应 在哪些相同主题被测试了并且是有些 更高为使用分开的小组的24和48 h间隔时间 主题。 当尼古丁在unilat-以后被应用了双向地30分钟 尼古丁的eral舌应用，重大大多数 主题选择了车被预处理的边(即，没预处理 尼古丁)作为有更强的激怒在2AFC (图1A)和被分配的显着更高的强度鼠 对那边(图1B)的ings。近似结果得到为 1和24 h interstimulus间隔时间，虽然与进步 减少在选择车的主题的百分比 在2AFC (图1A)的被对待的边。自已减低敏感 消散在48-h interstimulus间隔时间以后如见证 由缺乏在2AFC和强度规定值的意义 区别(图1A， B)。 辣椒素 在最初的应用，刺激性规定值极大是 (P<001)更高在边对待了与或者10或 100 ppm辣椒素和各自车相比 被对待的边(100 ppm辣椒素的表1)Ratings是 通常可比较与那些尼古丁的，虽然那里 是一些在之间小组可变性。 当双向地应用了10 ppm (33 lM)辣椒素 在它单边的应用，重大以后的5或1 h 多数主题选择了车被预处理的边作为hav- ing更强的激怒(图2A)和极大给了 那边的(图2B)更高的强度规定值。作用 在24 h以后去(图2A， 100 ppm的B)When (330 lM)是同样地应用的，重大大多数主题选择了 车被对待的边作为有更强的激怒 (图3A)和被分配的显着更高的强度鼠 对那边(图3B)的ings在所有interstimulus间隔时间 到48 h。 讨论 尼古丁的口头刺激性感觉的自已减低敏感 为24 h坚持了和在48 h以后不再重大的， 表明那，如果减低敏感仍然是存在作用 是相对地小的。从一个实验性立场，这些 结果表明在测试会议之间的2天的间隔时间 是充足避免尼古丁的重大延期生效， 虽然另外研究是否是需要的确定 作用是完全地缺席的。从一个实用观点， 包含足够的尼古丁产品的口头摄取 导致激怒，例如烟草烟雾，嚼对 bacco或者尼古丁胶，可能导致长时期的自己 减低敏感。
结果 尼古丁 在最初的应用,收视率的愤怒是明显的 cantly更高(P < 001)nicotine-treated侧com - vehicle-treated数目(表1)Initial度 类似的,interstimulus间隔1小时5% 在同一主题进行了测试,都有点 更高的24和48小时间隔,使用不同的 题目。 当尼古丁是30分钟后,应用双侧unilat -吗 eral语言应用的尼古丁,明显的多数 选择vehicle-pretreated科目侧(即不处理 用尼古丁)在2-AFC具有较强的刺激 (动作)和指定的显著高于大鼠-强度 到那边的奖金(图磅)Similar结果 1、24小时interstimulus间隔,尽管有进步 受试者中所占的比例下降的选择车辆- 在2-AFC治疗(图1A),self-desensitization 48-h消退之后interstimulus区间的表现 由于缺乏意义的2-AFC和强度等级 区别,B)(图1A。 辣椒素 在最初的应用、刺激性的评分均显著 (P < 001)更高的一面用10或 辣椒素相比万分之一的各自的车辆 治疗方面(表1)Ratings万分之一是对辣椒 一般相类似的尼古丁虽然那里 一些群体间的变异。 当十万分之一(33 lM)辣椒素用于双向吗 1小时后,要么5或其单方面的应用,具有重要的参考价值 多数的主体选择的vehicle-pretreated一边倍感- ing强刺激(图2)并给显著 高强度等级,一边(图2B)的效果 24小时后就走(图2)当万分之一(330 lM)是同样的应用,多数的主体选择吗 有较强的vehicle-treated一边愤怒 (图3A)和指定的显著高于大鼠-强度 到那边的奖金(图3B)interstimulus间隔 48小时了。 讨论 Self-desensitization口腔刺激性的尼古丁 持续24小时后,就不再重要48小时, 表明如果脱敏仍然呈现的效果 相对较小从实验的角度看,这些 研究结果表明,在为期两天的时间间隔,测试会话 就足以避免重大影响的尼古丁,结转 尽管可能需要进一步的研究来确定 这个效果完全不在从实用的角度看, 口头摄取含有足够的尼古丁 导致过敏,如吸烟、咀嚼来- bacco或尼古丁口香糖,很可能导致长期自我 脱敏治疗。
Results烟碱在上面用缩写名签应用评级的烦躁是signifi-黑话中特有地高(P<001)为烟碱-处理方面com-削去用车辆-处理小几1)Initial等级是相似对于5和1 hinterstimulus时间间隔 conditions在朝派哪一个同样的人科目被测验和是在某种程度上高对于24和48 h时间间隔那使用分开组的科目什么时候烟碱 was适用两边地30分钟下午unilat- eral舌的应用的烟碱a重要多数的科目是选择车辆预先处理方面即不预先处理用烟碱某样的人有强有力地烦躁在朝派2 AFC数字1A和分配在相当大的程度上高强度老鼠ings向那个方面数字1BSimilarresults得到为1 和24 hinterstimulus时间间隔尽管用a进步分子减少在朝派百分比的科目选择车辆处理方面在朝派在一48 hinterstimulus时间间隔这是被一缺少在2 AFC和强度评级差异图1A B中重要性证明之后,2 AFC图1AThe自身麻木不仁驱散在开头应用有刺激性等级上辣椒素是在相当大的程度上方面was用或者10或者和为 100 ppm辣椒素各自车辆处理小几Ratings相比100 ppm辣椒素处理的P<001更高右手击球员的左后方场地虽然有一些在中间组易变性,是通常可比较的那些为烟碱什么时候10 ppm33 lM辣椒素was适用两边地或者5或者它的1 h下午单方面应用a重要多数的科目选择车辆预先处理方面某样的人hav- ing强有力地烦躁数字2A和是让步在相当大的程度上高强度评级为那个方面数字2BThe影响was去下午24 h数字2A BWhen100 ppm330 lMwas同样适用a重要多数的科目选择车辆-把方面当作有更坚强烦躁((图3A)和给在相当大的程度上更高强度分配老鼠ings向那个方面(图3B)阿特 all interstimulus intervals out to 48 Discussion Self-desensitization of the oral irritant sensation of nicotine persisted for 24 h and was no longer significant after 48 h, indicating that if desensitization were still present the effect was relatively From an experimental standpoint,these results indicate that a 2-day interval between testing sessions is sufficient to avoid a significant carryover effect of nicotine, although additional studies would be needed to determine if the effect is completely From a practical viewpoint, the oral ingestion of products that contain enough nicotine to induce irritation,such as tobacco smoke,chewing to- bacco,or nicotine gum,is likely to induce prolonged self-
英语翻译毕业论文可以写某个电影或者某本书的翻译，开始也不太会，也是莫文网的高手帮忙的，很靠谱的说应用英语翻译呼唤理论指导大学英语翻译教学:现状与对策商务英语翻译中存在的问题与对策新世纪十年来商务英语翻译研究:回顾与前瞻国内商务英语翻译研究综述顺应理论视角下科技英语翻译切雅实证分析经济一体化环境下的商务英语翻译教学大学英语翻译教学存在的问题与对策语用观视角下的中医英语翻译教学实证研究翻译——找到源语的所指——对规划教材《商务英语翻译》误译译例的批判研究从功能对等角度看商务英语翻译高校科技英语翻译课程设置探讨功能对等理论指导下的商务英语翻译科技英语汉译的英语翻译技巧研究——以船舶英语文本中的汉译为例功能对等视角下的科技英语翻译论商务英语翻译的4Es标准关联理论在科技英语翻译中的应用——以Climate Change and Peak Oil文本的翻译为例大学英语翻译教学:问题与对策英语翻译专业本科生的笔译能力调查分析——以某师范大学英语翻译专业为例中国职业篮球俱乐部体育英语翻译人员现状及发展对策研究从目的论的角度下看商务英语翻译试论旅游英语翻译中的创造性论高职商务英语翻译教学中学生跨文化交际意识的培养试论近代国人英语翻译基于功能翻译理论的商务英语翻译教学任务型教学法在《商务英语翻译》教学中的运用跨文化因素对商务英语翻译的影响及调整策略商务英语翻译教学存在的问题与改革商务英语翻译与文化信息等值研究大学英语翻译教学教材编写探讨东西方文化差异对商务英语翻译的影响顺序分析在科技英语翻译中的应用——以翻译项目《大气污染排放系数手册》为案例从关联理论分析法律英语翻译中的文化差异及其翻译补偿商务英语翻译原则探讨商务英语翻译中的文化与语用因素研究Advanced Systematic Golf高尔夫技术英语翻译项目的实践报告
毕业设计的英文翻译有两类 第一种,是将毕业实际中的摘要用英文进行翻译 第二种,是自己找一篇与毕业设计相关的论文,将它翻译为英文,翻译的时候可以用专业的翻译工具
毕业设计不会做，抄也要讲究方法作为一个已经毕业了的大学生，在做毕业设计的过程中，无论是设计成果的研究还是毕业论文的撰写，不可回避的一个问题就是抄袭。作为一个过来人，我想说的是，做毕业设计难免会有抄袭的现象，但是一定要掌握方法，千万不要盲目的抄完了事，那样做是非常危险的。有的同学看都不看就抄到论文上去了，有的同学拿着别人做完的东西都不研究一下就参加答辩去了。我就听过一个活生生、血淋淋的例子—— 老师问：“你这段代码是什么意思？” 答：“我不知道。” 老师又问下一段代码，又不知道，老师问：“这是你做的吗？” 答：“不是，老师给的。”其结果可想而知了。 你们想想，那些东西都是往届毕业生做出来的，老师们能看不出来吗？掩耳盗铃，自欺欺人，大家都是成年人，我想不用多说了吧。 大家在完成毕业设计的过程中肯定会遇到各种各样的现实性困难，成果做不出来了怎么办?论文写不出来了怎么办？外文文献不会翻译怎么办？其实这都好办，世界上再难的技术也是人做出来，没有成果就找个现成的东西；论文写不出来就多看几本书，多引用书里的内容；外文水平不高就用翻译软件。总之一句话，你有张良计，我有过墙梯，物竟天择，适者生存。文章转自 众赏文库 毕业设计论文,专业文档下载
去百度搜索，需要什么语言直接在线翻译就OK啦