狭缝式熔体微分电纺工艺参数对射流间距的影响

采用自主设计的狭缝式熔体微分静电纺丝装置对聚丙烯（PP）材料进行熔体静电纺丝,研究了纺丝电压、纺丝距离和纺丝温度3个纺丝参数对射流间距的影响。结果表明,射流间距随纺丝电压的升高而减小;射流间距随纺丝距离的减小而增大,但当纺丝距离低于80 mm并继续减小时,射流间距保持不变;射流间距随纺丝温度的升高而减小,当纺丝温度达到230 ℃并继续升高时,射流间距保持不变;当纺丝电压为60 kV,纺丝距离为100 mm,纺丝温度为245 ℃时,射流间距最小,可达3.3 mm。     

纺丝液性质对静电纺丝的影响研究进展

静电纺丝技术是制备高品质纳米纤维的最有效方法之一,纺丝液的性质对静电纺丝效果具有重要的影响。本文简要介绍了静电纺丝的原理,从纺丝液黏度、导电性、表面张力三个方面综述了纺丝液性质对静电纺丝的影响,最后指出静电纺丝技术存在的问题及未来的发展。     

聚乙烯醇静电纺丝纳米纤维的制备及形貌研究

利用静电纺丝技术制备聚乙烯醇（PVA）纳米纤维材料,通过正交试验调节制备过程中纺丝电压、纺丝距离和纺丝溶液浓度等工艺参数,探究其对PVA纳米纤维直径大小、直径分布以及纤维形貌的影响。结果表明,影响纳米纤维形貌的主要因素排序是纺丝溶液浓度＞纺丝距离＞纺丝电压,并确定最优水平组合为纺丝电压为20 kV,PVA纺丝溶液浓度为6 %(质量分数,下同),纺丝距离为12 cm。     

聚合物离心静电纺丝技术研究进展

简述了离心静电纺丝技术的工作原理,对国内外近期离心静电纺丝的研究进展进行了综述.总结了离心静电纺丝的成纤机理,根据纺丝材料特性,将离心静电纺丝分为溶液离心静电纺丝和熔体离心静电纺丝两类,并将这两类纺丝方法的装置和工艺创新进行了分类,总结了各种装置的结构特征和优缺点,并对其工艺参数进行了分析.最后对离心静电纺丝微纳米纤维...     

圆形纺丝箱与长方形纺丝箱结构设计的比较

从纺丝箱强度计算、箱体焊接结构、纺丝箱内的传热计算、保温层壁厚计算等方面对PET熔体圆形纺丝箱与长方形纺丝箱的结构设计进行了比较。圆形纺丝箱箱体壁厚是长方形纺丝箱箱体壁厚的1/2,箱体质量轻1/2以上。从结构上看,圆形纺丝箱的焊缝要少于长方形纺丝箱焊缝,采用圆形纺丝箱可以节省制造成本。所需加热能源是方形的2/3,可以节约生产成本。     

无纺丝头的熔融纺丝法

近年来,合成纤维纺丝的新工艺和新技术不断出现,如薄膜撕裂纤维法、无纺丝头纺丝法、瞬时纺丝法和相分离纺丝法等。本文专介绍无纺丝头熔融纺丝法(简称无头纺丝法)。 在常规熔融纺丝中,纤维成形是熔融聚合物强制通过纺丝头喷丝板的细孔予以实现,这     

聚苯乙烯的制备及可纺性研究

采用微乳液聚合法,以十二烷基磺酸钠为乳化剂(SDS)、过硫酸铵为引发剂(APS)、苯乙烯为原料合成了聚苯乙烯(PS)。运用静电纺丝工艺对聚苯乙烯进行纺丝,探究纺丝液、纺丝电压、外加磁场和聚苯乙烯摩尔质量对聚苯乙烯纺丝纤维可纺性影响。运用扫描电子显微镜(SEM)对聚苯乙烯纺丝纤维的形貌进行表征,结果表明,一定范围内的纺丝液浓度、纺丝电压、外加磁场和聚苯乙烯摩尔质量均对纺丝纤维结构产生重要影响。     

聚合物离心纺丝模式的研究现状

阐述了离心纺丝的基本原理,介绍了溶液、熔体离心纺丝及其扩展方法,如离心静电纺丝及气流辅助离心纺丝等不同离心纺丝模式的发展现状,分析了不同工艺参数对纤维特征参数的影响,对离心纺丝的发展具有一定借鉴意义。     

醋酸纤维素的熔体静电纺丝

静电纺丝是一种利用聚合物溶液或熔体在强电场作用下形成喷射流,制备连续纳米纤维的工艺。熔体法静电纺丝技术不使用溶剂,绿色环保。探索了改性醋酸纤维素(CA)的熔体静电纺丝技术,考察了不同纺丝条件如纺丝温度和纺丝电压对纤维直径的影响,并通过MFR测试、纺丝纤维XRD表征、SEM分析表征了不同纺丝实验条件下制备纤维的性能,得出醋酸纤维素在熔体温度为190℃,纺丝距离为14 cm,纺丝电压为63 k V时获得的纤维直径最小。     

熔体静电纺丝技术及其在生物医学中的应用

熔体静电纺丝技术不使用溶剂,可制备连续的超细纤维,在生物医学领域有着广泛的应用。从流体黏度、射流特点、纤维直径、纺丝效果方面比较了熔体静电纺丝与溶液静电纺丝的差异;介绍了近年来熔体静电纺丝的技术进展,如激光加热熔体静电纺丝技术、同轴熔体静电纺丝技术,以及熔体静电纺丝直写技术等;综述了熔体静电纺丝技术在组织工程、伤口敷料和药物释放方面的应用;指出熔体静电纺丝应进一步优化加工工艺,获得具有适度自粘结结构的支架,从而提高其应用性。     

颗粒介质用机械密封热力耦合变形及摩擦磨损研究

在含有颗粒介质的工作环境中下,硬质材料配对机械密封环的热力耦合变形和摩擦磨损对机械密封的泄漏和使用寿命起着至关重要的作用。考虑动静环和颗粒介质的摩擦,试验测定了摩擦系数,建立了动静环热力耦合的有限元计算模型,研究了WC-Co硬质合金和无压烧结碳化硅（SSiC）陶瓷两种硬质材料密封的温度场和端面变形规律,分析了不同工况下的密封间隙变化规律。试验测试分析了密封环温度、磨损前后的泄漏及表面粗糙度,讨论了端面的磨损机理,验证了计算模型的准确性。结果表明：考虑动环磨粒摩擦热的有限元模型能准确地预测密封的温度和端面变形;耦合作用下动静环端面呈现外径脱离、内径贴合的变形,且变形差异程度随压差和转速的增大而加剧;变形导致端面磨痕分布不均匀,内径磨痕较严重。WC-Co硬质合金配对密封环的端面变形小、泄漏量小,高硬度WC颗粒对Co基体能产生很好的“阴影效应”,具有良好的耐磨粒磨损性能。SSiC陶瓷材料韧性差,易产生片状磨屑,形成过渡型磨粒磨损,材料耐磨性较差,泄漏量增加明显。在磨粒工况下,WC-Co硬质合金机械密封具有泄漏小、耐磨性强的特点。研究结果为颗粒介质中机械密封的材料应用及设计优化提供了参考。     

Some gas phase reactions during the firing of magnesite-chromite refractories in a tunnel kiln

Conclusions A correlation is shown between the high-temperature, physicochemical processes in basic refractories, changes and reactions in the gaseous phase, and the nature of the wear of the roof of a tunnel kiln.As a result of dissociation, oxidation, and volatilization the waste gases are enriched with vapors of alkalis, CrO₃, sulfur trioxide, and oxides of iron and magnesium, and become corrosive with respect to the kiln lining. The reaction of the oxides vapors with each other and with the lining of the roof and their condensation determines the nature of the wear in the magnesite-chromite refractories, the chemical and mineral compositions of the resulting deposits and crusts. The main source of alkalis and sulfur trioxide is the sulfite yeast dregs (sulfite lye) present in the goods being fired.We determined the temperature relationship with the composition and amounts of deposits and crusts. Carcase and skeletal deposits and crusts formed on the firing section of the kiln, mainly periclase and spinel compositions; in the warming-up section the deposits were brittle, granulated, consisting of sulfates, chromates, chromium oxide, periclase, and spinels.It was found that the deposits on the walls of the pores in the MKhS refractories consist of sulfates and chromates, forming solid solutions.Translated from Ogneupory, No. 5, pp. 13–16, May, 1980.     

Price evolution of foods and nutriments in Mexico from 1973 to 2004

The aim of this study was to know the price changes of foods and nutriments in México during the last three decades. To this end, two sets of data were analyzed: the National Consumer Prices Index for 1973 to 2003, and quotations of food prices for 1990, 1995, 2000 and 2004. Cost estimates were calculated for 100 kcal, 10 g of saturated fat, 100 mg of cholesterol, 10 g of fiber and 1 mg of iron. Regression models were used to analyze the association between nutrient and energy's costs and energetic and nutrimental densities. Our results lead to infer that that in M6xico, the structure of foods prices differed between the eighties and the nineties decades. In the former, vegetables and corn and wheat derived foods had the lowest price increment, whereas their price had the largest increment in the following decade. On the other hand, the prices of fresh meat of cattle and pig, and of fish and seafood rose during the eighties but became cheaper during the nineties. The differences in prices of the meat are inversely related to their energy density and nutrimental value: lean meat became more expensive that those with more fat (i.e., more energy and cholesterol). Canned fish (tuna and sardine), eggs and poultry became cheaper at the turn of the eighties. The prices of the majority of oils and fats have increased less than the inflation of the group of food. Processed and industrialized foods became cheaper than the fresh ones. The energy density of the foods is negatively correlated to their cost. The implications of our results are discussed in terms of public policies.     

HD低温蒸发系统中填料蒸发器传质传热的分析

通过研究系统中填料蒸发器的蒸发传质传热过程以及两相流动特性，采用计算流体力学（computational fluid dynamics，CFD）中离散相与连续相耦合的方法来模拟规整填料内部通道的蒸发传质传热过程，实现了填料蒸发器中两相传质传热的过程以及液滴流动的可视化，为研究气液两相在规整填料内的流动提供了一种模拟方法。通过与实验结果的比较，最终选用RNG k-ε湍流模型来分析规整填料内部气液两相传质传热以及流动情况。数值模拟研究了规整填料板间距对填料内部气液两相传质传热以及液滴运动影响，发现随着板间距的增大，填料内部压力降逐渐降低，出口空气中水蒸气的含量不断减小，液滴蒸发速率降低，液滴进出口质量差减小，气相出口温度逐渐降低，蒸发传质传热效率降低。随着气速的增大，出口空气中水蒸气的含量不断减小，液滴蒸发速率增加，气相出口温度降低，气液两相传质传热效率降低。     

气泡在颗粒床层表面的生成脱离行为

试验研究了气泡在颗粒床层表面的生成脱离过程及其行为特性,利用高速摄像技术揭示了进气管管径、颗粒床层高度、颗粒粒径等因素对气泡脱离直径及其生成周期的影响规律,对比分析了颗粒床层表面和进气管管口的气泡生成脱离行为差异。研究结果表明：在1500～3000μm粒径范围的床层表面所生成气泡的初始形态相对更扁小,气泡也更快向扁平状演变;颗粒粒径的增大使得进气流量对气泡形态的影响减弱;管径和颗粒床层高度的增大可以有效促进气泡脱离直径的增长,但延缓了气泡的生成脱离,增加了气泡的生成周期;颗粒粒径对气泡生成周期的影响随着进气流量的增大而逐渐减弱;气泡在颗粒床层表面和管口的生成脱离行为存在显著差异,相比之下,150～300μm粒径范围的颗粒床层对气泡的生成脱离具有更明显的阻碍作用,其表面所生成气泡的脱离直径和生成周期相对较大。     

民用工业中复合材料桁架的应用和发展

本文叙述了复合材料桁架的构造、分类和计算方法,突出了复合材料桁架的优越性能和在民用工业中的应用前景;在分析大量文献资料的基础上阐述复合材料桁架杆件的多种加工工艺,并比较不同截面形式对杆件性能的影响;探讨复合材料杆件的破坏机理和分析方法,介绍节点的类型和各自的特点,提出节点及连接部位存在的关键问题;根据国内外复合材料桁架的研究和应用现状,阐述了复合材料桁架的性能和不同的设计方法,总结归纳影响复合材料桁架性能的关键因素和设计中存在的一些问题,并提出改进杆件设计、节点设计和优化复合材料桁架的建议。     

Fast gas combustion in systems with hydraulic resistance

Various aspects of the sonic velocity regime, one of the steady-state regimes of filtration combustion of gases, is analyzed. The conditions and region of existence of the regime, the velocity and structural characteristics of the combustion wave, the gas ignition and combustion mechanisms, conditions for the stabilization of the wave velocity, and regime transitions are considered. A characteristic feature of the regime is the presence of a pressure wave in the zone of turbulent flame due to the choking of channels and narrowings. The main factors determining the nature and properties of the sonic velocity regime are the hydraulic resistance, piezo diffusion, the energetics of the mixture, the compressibility and turbulence of the gas, and the reactivity of the mixture at high pressures and temperatures. The sonic velocity regime is a unique and intriguing combustion regime which is promising for applications.     

世界油气主产国油气资源管理的基本经验及启示

油气是重要的战略资源,关系国计民生。随着工业化和城镇化的加速推进以及汽车进入普及期,我国油气供需形势日趋严峻。解决我国油气供应不足的问题。应首先立足于开发利用国内的油气资源,不断提高自给水平,然而却存在管理体制和政策的掣肘。世界油气主产国都不断改善其油气资源开发利用的管理体制与政策,促进更加有效与合理地开发利用和保护油气资源。本文总结了该领域的国际经验,从加强油气资源法律法规体系建设、促进油气资源管理体制改革、完善油气资源矿业管理等方面提出了对我国的启示和改革建议。     

胜利坨11南交联聚合物驱采出液油水界面性质及乳状液稳定性研究

用界面张力仪、表面粘弹性仪和Zeta电位仪测定了胜利坨11南原油模拟油与采出水间的界面特性,研究了聚合物、交联剂及弱凝胶对这些界面特性及乳状液稳定性的影响。结果表明,模拟水中加入聚合物、弱凝胶后,模拟水与原油模拟油间的界面张力、界面剪切粘度和油滴表面的Zeta电位绝对值增加,原油与含聚合物和弱凝胶的模拟水间所形成的W/O和O/W乳状液稳定性随聚合物、弱凝胶浓度增加而增强;交联剂对原油模拟油与模拟水间的界面性质及所形成的乳状液稳定性影响很小。     

Effects of carboxylated styrene-butadiene latex nanoparticles on channeling leakage and pore structure of oil well cement

The exploitation efficiency of oil and gas resources depends on the cementing quality. In cementing engineering, interlayer migration occurs in the underground gas layer with cement hole as the main channel, which seriously threatens the sealing integrity of cement casing and leads to the failure of cementing operation. To improve the gas migration control ability of oil well cement (OWC), two carboxylated styrene-butadiene latex nanomaterials styrene butadiene latex containing itaconic acid and sodium p-styrene sulfonate (SBSI) and styrene-butadiene latex containing methacrylic acid and sodium p-styrene sulfonate (SBSM) were synthesized. The effects of SBSI and SBSM with different carboxyl structures on the gas migration control ability and pore structure of cement were investigated. The results show that the latex is densely packed on the cement matrix through the dissociation and adsorption behavior of carboxyl groups, and the smaller particle size and lower adsorption are more conducive to the formation of the film. The introduction of latex effectively shortened the transition time of cement gel state and significantly reduced the permeability of interlayer material migration. Compared with OWC, the transition time of cement containing SBSI and SBSM latex (SBSI/OWC and SBSM/OWC) decreased from 28 to 18 and 17 min, respectively, and the filter loss decreased from 60 to 40 and 36 mL, respectively. The isolation effect of the latex film on the interlayer gas and the provision of mechanical support have greatly improved the gas migration control ability of the cement and ensured the cementing quality. In addition, the refinement of cement pore structure caused by latex brings better rheological and mechanical properties to cement. This study clarified the change of latex in the gel transition stage of OWC from liquid to solid and revealed the mechanism of latex on the internal structure change of cement. It broadens the application range of latex nanomaterials in the field of OWC and provides a new possibility for the use of OWC in high temperature and high salt environment.