Gas-phase synthesis of nanoparticles: scale-up and design of flame reactors

The scale-up and design of flame aerosol reactors are investigated for synthesis of silica and titania nanoparticles. In specific, coflow burners of different dimensions are studied at various precursor, fuel, and oxygen flow rates. The influence of the flame enthalpy content on product primary particle size is investigated by changing the fuel from methane to propane or hydrogen. Operation lines relating product particle size with reactant outlet conditions, burner size, and flame enthalpy are developed, showing how the different reactors can produce silica or titania nanoparticles of the same size. A scale-up procedure developed for fumed silica is extended to the synthesis of titania nanoparticles covering production rates of 2-200 g/h. At high fuel-oxidant velocity difference at the burner outlet, the operation of diffusion flame reactors converges to that of premixed ones.     

Continuous hydrogenation of fats and fatty acids at short contact times1

Continuous hydrogenation of fats and fatty acids using suspended catalysts was studied in a vertical flow reactor packed with Raschig rings. A short time of reactive contact of the fat or the fatty acid with the catalyst and hydrogen is the unique feature of this system. A nickel catalyst used in the hydrogenation of soybean oil gave a reduction of 40-50 iodine value units per min, small amounts oftrans-isorners (10-20%), large proportions of linoleate in unreduced octadecadienoyl moieties (70-80%), and nonselective reduction of polyunsaturated acyl moieties (linoleate selectivity ratio 1-3). Another nickel catalyst, used in the hydrogenation of tallow fatty acids, also gave a reduction of 40-50 iodine value units per min and nonselective reduction of polyunsaturated fatty acids. A copper chromite catalyst used in the hydrogenation of soybean oil gave a reduction of 10-15 iodine value units per min, low levels oftrans- isomers (10-15%), and selective reduction of linolenoyl moieties (linolenate selectivity ratio 4-6). Composition of positional isomers of cis- andtrans-octadecenoyl moieties in partially hydrogenated products obtained both with nickel and copper chromite catalysts reveals that essentially the same mechanisms of isomerization are involved in continuous hydrogenation at short time of reactive contact as in batch hydrogenation. 1The terms “linoloyl” and “linolenoyl” are used throughout to designate9-cis, 12-cis-octadecadienoyl and 9-cis, 12-cis, 15-cis- octadecatrienoyl groups, respectively.     

Elastic deformation of a hypoid gearbox

High load carrying capacity in the gear mesh can be achieved when the contact load is well distributed. Designing an adequate tooth flank geometry requires a thorough calculation approach. This is particularly important for automotive hypoid gearboxes with aluminum housing. In this paper, the deformation analysis of housing, bearings and shafts for a hypoid gearbox is validated by measurements at a static test rig. The challenge of compensating friction effects to get high-quality measurement results is successfully met by the presented approach.There are several computer programs to calculate the elastic deformation behavior of the system shaft-bearing-housing. Most of the calculation programs use analytical approaches. The advantage of these programs, in comparison to a full FEM approach, is an efficient parameterization of gears and a very short calculation time, while delivering high precision results. The deformation behavior of housings can be considered in different ways. The deformation behavior of a bearing seat can be modelled by its stiffnesses. For housings with lower stiffnesses (for example aluminum housings), crossover influences become more and more important. The deformation behavior of a housing can be taken into account by a stiffness matrix. The stiffness matrix of a housing can be determined by using the finite elements method. Therefore, the complex elastic deformation behavior of housings can be considered in analytical calculation approaches. Within the scope of a research project, investigations have been made to validate the calculated elastic deformations of the shaft-bearing-housing system. For this purpose, deformation measurements of a test gearbox were taken by using a 3D coordinate measuring machine. The test gearbox is static and consists of a hypoid gearbox for automotive applications. The input torque is provided by a lever mechanism. The elastic deformation of the test gear box has been measured and compared to calculation results. Therefore, different approaches of modelling the elastic deformation behavior of the housing can be validated and compared to each other.     

Self-lubricating gears with oil-impregnated sintered materials

This study shows the first results on the operating behavior of self-lubricating gears based on oil-impregnated sintered material. The term self-lubrication is referred to as oil that bleeds from the open-pored sintered gear and providing lubrication to the gear contact. Experiments were carried out at the FZG efficiency gear test rig. Thereby, the pinion was made of open-pored, case-hardened sintered steel and impregnated with oil, and the wheel was made of conventional case-hardened steel. The total loss in torque and the bulk temperatures of the pinion and wheel were measured for various operating conditions defined by load and circumferential speed. The mean coefficient of friction in the gear contact was derived from the torque loss measurements. Results confirm that self-lubricating tribological systems with oil-impregnated sintered materials can be transferred from model test rigs to gears. The mean coefficient of friction shows the order of magnitude of externally lubricated gears. The tooth flanks after test runs show partially noticeable wear. As the heat dissipation of self-lubrication is limited, bulk temperatures and thermal load limits influence operating behavior significantly. Further work will focus on understanding the mechanisms of the lubricant film formation of self-lubricated, highly-loaded EHL contacts and on extending the thermal load limits.     

Consistent integration of models based on views of meta models

The complexity of large system models in software engineering nowadays is mastered by using different views. View-based modelling aims at creating small, partial models, each one of them describing some aspect of the system. Existing formal techniques supporting view-based visual modelling are based on typed attributed graphs, where views are related by typed attributed graph morphisms. Such morphisms up to now require a meta model given by a fixed type graph, as well as a fixed data signature and domain. This is in general not adequate for view-oriented modeling where only parts of the complete meta model are known and necessary when modelling a partial view of the system. The aim of this paper is to extend the framework of typed attributed graph morphisms to generalized typed attributed graph morphisms, short GAG-morphisms, which involve changes of the type graph, data signature, and domain. This allows the modeller to formulate type hierarchies and views of visual languages defined by GAG-morphisms between type graphs, short GATG-morphisms. In this paper, we study the interaction and integration of views, and the restriction of views along type hierarchies. In the main result, we present suitable conditions for the integration and decomposition of consistent view models (Theorem 4.1) and extend these conditions to view models defined over meta models with constraints (Theorem 5.1). As a running example, we use a visual domain-specific modelling language to model coarse-grained IT components and their connectors in decentralized IT infrastructures. Using constraints, we formulate connection properties as invariants.     

Das Identitätsproblem der tiefen Hirnstimulation und einige seiner praktischen Implikationen

Definition of the problem Questions of personal identity play a prominent role in the developing debate within medical ethics on the ethical implications of deep brain stimulation (DBS); however, their exact role is unclear. Argumentative strategy Since personal identity is also discussed in the more theoretical branches of philosophy, this essay focuses not only on the question of informed consent in DBS but also tries to better understand what the debate on DBS and personal identity is all about. Only then can the role and set up of informed consent in identity-affecting DBS be accurately determined. Conclusion There is reason to believe that in identity-affecting DBS the common way to legitimize medical interventions via informed consent should be replaced by a two-step procedure.     

缓冲胶结的反应-传递模型的试验校正

在KBS-3核废料储存库的早期及非恒温演变期,热梯度变化能改变膨润土缓冲层的矿物特性,且由于矿物质沉淀作用,黏土颗粒将相互胶结起来.据此,使用已发表的有关结晶岩石中缓冲黏土的水-热转换的试验结果,研究并评估一种缓冲胶结的反应-传递模型.模型的预测值能够定性地与高温下缓冲区的观测试验值相吻合,表明次生矿物的沉淀(无水石膏(无定形二氧化硅(opal-CT)(方解石)和由Na基蒙脱石变为Ca 基蒙脱石(皂石的相交替过程.与现场观测中的一种情况不同的是,模型没有预测出这一区域中石英、高岭土和长石的大量溶解,这种不一致现象可能是由于缺乏热动力基本数据造成的,使得在高岭土-蒙脱石混合地层中高电荷蒙脱石变为低电荷蒙脱石过程中的水-热转换在模型中不能加以表示.然而,在整体上模型预测与试验观测还是较为符合的.这表明,用已知的时间-温度及再饱和过程的试验数据,该模型能够用于对KBS-3近场潜在的缓冲胶结进行长至几百年的敏感性分析.     

Analysis of Release and Role of Benzyl Cyanide in Male Desert Locusts, Schistocerca gregaria

Volatiles emanating from living Schistocerca gregaria at various stages of development were trapped by means of a closed-loop-stripping system. Benzyl cyanide was previously identified with GC-MS methods as a volatile that was exclusively released by adult mature gregarious males. The amount of BC released depended on the number of males per group. Mature female locusts did not stimulate the release of benzyl cyanide in gregarious males. After physical isolation of previously grouped males, a steady reduction in benzyl cyanide release was observed. After regrouping the isolated males, BC emission was restored. In olfactometer bioassays, benzyl cyanide had a strong repellent effect on gregarious mature males but only a weak one on immature males. The possible origin and role of benzyl cyanide in sexual behavior are discussed.