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1.
采用等电点结晶法,对液膜法提取的苯丙氨酸内相的模拟浓缩液进行了结晶工艺的研究。对不同操作温度,初始浓度和外界添加物影响下结晶质量的考察结果表明:只有控温在转化点温度以上才能得到优良的α-晶型;盐析剂氯化钠的加入对提高收率效果显著,乙醇的加入可以提高产品的纯度;保持较高的初始浓度对产生α-晶型和提高收率均有利。  相似文献   

2.
PVF和CaHPO4对Nylon6的热行为和晶型的影响   总被引:3,自引:0,他引:3  
利用DSC法研究了甲酸部分酯化聚乙烯醇(PVF)和二价金属盐CaHPO4对晶态-非晶态Nylon6/PVF共混体系中Nylon6的熔融、结晶及晶型结构的影响.结果表明,非晶态PVF虽降低了Nylon6的结晶能力,却使Nylon6能同时形成α和γ两种晶型;γ晶型的相对含量(Iγ)随共混物中PVF含量的增加而增加,而α晶型则相反;在相同的共混组成条件下,CaHPO4有利于Nylon6γ晶型形成.非等温结晶动力学结果表明,非晶态PVF对Nylon6的结晶生长速率和结晶生长方式均有显著影响;CaHPO4导致Nylon6从熔体中结晶出现前期和后期结晶,前期和后期结晶的结晶生长速率均明显增大,表明CaHPO4影响Nylon6的成核并起成核剂的作用.  相似文献   

3.
酸法合成针形超微粒α—FeOOH过程研究:I.晶种制备   总被引:5,自引:2,他引:5  
探讨了反应温度、通气量、搅拌转速、初始混合状态等对晶种制备过程氧化速率及晶种形态的影响。发现晶种制备阶段存在溶解-氧化动态平衡过程,此时溶液pH值和[Fe^2+]基本不变;在25 ̄50℃范围内可制得形态较好的单一相α-FeOOH;随通气量和搅拌转速增加,晶种粒子粒度分布趋于均匀,枝叉和孪晶减少;初始混合状态对晶种最终形态影响不大。  相似文献   

4.
间规聚苯乙烯的等温熔体结晶   总被引:1,自引:0,他引:1  
用WAXD、FTIR和DSC方法研究了间规聚苯乙烯(S-PS)的等温熔体结晶行为。发现不同温度tc下结晶所得的s-PS均为α和β两晶型的混合物。高温下(tc>245℃)结晶有利于β晶型的生成,相对分子质量和间规度的提高有利于形成α晶型。随tc的升高,结晶样品的熔程变窄,晶体的完善程度增加。  相似文献   

5.
探讨了反应温度、通气量、搅拌转速、初始混合状态等对晶种制备过程氧化速率及晶种形态的影响。发现晶种制备阶段存在溶解。氧化动态平衡过程,此时溶液pH值和[Fe ̄(2+)]基本不变;在25~50℃范围内可制得形态较好的单一相α-FeOOH;随通气量和搅拌转达增加,晶种位子粒度分布趋于均匀,枝叉和孪晶减少;初始混合状态对品种最终形态影响不大。  相似文献   

6.
溶析结晶广泛用于有机工业结晶过程,但目前溶析结晶过程普遍存在着以下问题;晶体主粒度小,变异系数高,产品过滤分离难度大,杂质含量高,针对这些问题。本文研究了溶析结晶体系的介稳区性质,并采用了如下几种强化方法;用压力溶解和静置冷却来提高过饱和度;在沉淀中添加表面活性剂以及采用弹性叶片摩擦和超声波刺激来提高成核速度;动静态交替育晶减少生长分散;加入促进构型转变的物质获得所需晶型的晶体;按照最佳操作程序流  相似文献   

7.
α—芳氨基乙酰芳胺的合成及除草活性   总被引:1,自引:0,他引:1  
α-芳氨基乙酰芳胺的合成路线作了小结,优化了传统反应条件发现加入碘化 催化剂后,反应时间短,条件温和,收率高,在优化条件下合成了11个α-芳氨基乙酰芳胺;对产物进行了^1HNMR和MS表征;除草活性测试表明产物对双子叶植物的根有较好的抑制作用。  相似文献   

8.
超支化聚合物对尼龙6结晶及力学性能的影响   总被引:1,自引:0,他引:1  
超支化聚合物(HBP)作为共混组分加入到尼龙6(Nylon 6)基体中,有望在改善其熔体加工性能的同时提高产品性能.采用DSC、X-ray、力学测试等手段研究了不同质量分数的HBP对Nylon 6结晶性能、力学性能等的影响.结果表明:HBP的加入使得Nylon 6的结晶度有一定程度的提高,Nylon 6的晶型发生变化,γ-晶型弱化,由α-晶型占据主导地位,而且HBP在Nylon 6基体中能够均匀分散,同时提高了Nylon 6的力学性能.  相似文献   

9.
采用离子束溅法,在单晶Si(100)基片上制备CNx薄膜。研究了基片温度对CNx薄膜性能和结构的影响。结果表明:随着基片温度的提高,薄膜生长致密,表面光滑;薄膜硬度逐渐提高,但温度升高到200℃后,硬度增加缓慢。同时,基片温度升高使薄膜中的N含量增加,促进C-N化合物结晶。X射线衍射结果证明在850℃时,薄膜中产生α-C3N4晶相。  相似文献   

10.
以空气-NaHCO3饱和液为介质,在新型碳化塔的模拟塔内,测定了气体流速ug、液体流速uL、液相内循环速度uc、晶浆平均停留时间τ等参数对结晶动力学的影响;重点研究聚丙烯酸钠加入碳化塔后动力学参数的变化规律.按Randolph和Larson模型计算了结晶成核速率B0和晶体生长速率G,并建立了结晶动力学方程.结果表明,添加聚丙烯酸钠,有利于增大结晶颗粒,改善重碱结晶质量.  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

14.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

15.
正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-  相似文献   

16.
We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-  相似文献   

17.
正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that  相似文献   

18.
For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the  相似文献   

19.
Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of  相似文献   

20.
<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with  相似文献   

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