Catalytic cracking of 1-butene to propene and ethene on MCM-22 zeolite

Catalytic cracking of butene to propene and ethene was investigated over HMCM-22 zeolite. The performance of HMCM-22 zeolite was markedly influenced by time-on-stream (TOS) and reaction conditions. A rapid deactivation during the first I h reaction, followed by a quasi-plateau in activity, was observed in the process along with significant changes in product distributions, which can be attributed to the fast coking process occurring in the large supercages of MCM-22.

Effect of syngas addition on lower alkene production by the oxidative cracking of hexane

The lower alkene production by the gas-phase oxidative cracking (GOC) or catalytic oxidative cracking (COC) of hexane (C6) with added syngas was investigated. The addition of syngas to the COC process could effectively enhance the selectivity to lower alkenes and decrease the selectivity to COx, because of the preferential reaction between O-2 with H-2 contained in the syngas, whereas it has little effect on the conversion of C6 and product distribution in the GOC process. The high selectivity to lower alkenes of 70% and low selectivity to CO, of 6% at C6 conversion of 66% were achieved over 0.1% Pt/MgAl2O4 catalyst. The COC process of C6 combined with the syngas in the feed could directly produce a gas mixture of lower alkenes, H-2, and CO, which usually is a suitable feedstock for the hydroformylation process.

Production of light olefins and aromatic hydrocarbons through catalytic cracking of naphtha at lowered temperature

Naphtha catalytic cracking were carried out at 650 degrees C over modified ZSM-5. Light olefins and BTX could be obtained over the catalysts. The products showed variable distribution with different catalyst modification. Some modification, such as Fe, Cu and La favored the BTX generation and P and Mg modification favored the light olefins production. In N-2 stream cracking catalyzed by LaZSM-5, more than 50% naphtha feed were converted to BTX, while in steam cracking, with an improved modified catalyst, P, La/ZSM-5, naphtha can be converted to light olefins with high activity and long-term stability.

Butene catalytic cracking to propene and ethene over potassium modified ZSM-5 catalysts

Catalytic cracking of butene over potassium modified ZSM-5 catalysts was carried out in a fixed-bed microreactor. By increasing the K loading on the ZSM-5, butene conversion and ethene selectivity decreased almost linearly, while propene selectivity increased first, then passed through a maximum (about 50% selectivity) with the addition of ca. 0.7-1.0% K, and then decreased slowly with further increasing of the K loading. The reaction conditions were 620 degrees C, WHSV 3.5 h(-1), 0.1 MPa 1-butene partial pressure and 1 h of time on stream. Both by potassium modification of the ZSM-5 zeolite and by N(2) addition in the butene feed could enhance the selectivity towards propene effectively, but the catalyst stability did not show any improvement. On the other hand, addition of water to the butene feed could not only increase the butene conversion, but also improve the stability of the 0.7%K/ZSM-5 catalyst due to the effective removal of the coke formed, as demonstrated by the TPO spectra. XRD results indicated that the ZSM-5 structure of the 0.07% K/ZSM-5 catalyst was not destroyed even under this serious condition of adding water at 620 degrees C.

The management of health library outreach services: evaluation and reflection on lessons learned on the VIVOS project

Yeoman, A. J., Cooper, J. M., Urquhart, C. J. & Tyler, A. (2003). The management of health library outreach services: evaluation and reflection on lessons learned on the VIVOS project. Journal of the Medical Library Association, 91(4), 426-433. Sponsorship: Resource

Portable, Fiber-Based, Diffuse Reflection Spectroscopy (DRS) Systems for Estimating Tissue Optical Properties.

Steady-state diffuse reflection spectroscopy is a well-studied optical technique that can provide a noninvasive and quantitative method for characterizing the absorption and scattering properties of biological tissues. Here, we compare three fiber-based diffuse reflection spectroscopy systems that were assembled to create a light-weight, portable, and robust optical spectrometer that could be easily translated for repeated and reliable use in mobile settings. The three systems were built using a broadband light source and a compact, commercially available spectrograph. We tested two different light sources and two spectrographs (manufactured by two different vendors). The assembled systems were characterized by their signal-to-noise ratios, the source-intensity drifts, and detector linearity. We quantified the performance of these instruments in extracting optical properties from diffuse reflectance spectra in tissue-mimicking liquid phantoms with well-controlled optical absorption and scattering coefficients. We show that all assembled systems were able to extract the optical absorption and scattering properties with errors less than 10%, while providing greater than ten-fold decrease in footprint and cost (relative to a previously well-characterized and widely used commercial system). Finally, we demonstrate the use of these small systems to measure optical biomarkers in vivo in a small-animal model cancer therapy study. We show that optical measurements from the simple portable system provide estimates of tumor oxygen saturation similar to those detected using the commercial system in murine tumor models of head and neck cancer.

Birth-death processes with an instantaneous reflection barrier

A new structure with the special property that an instantaneous reflection barrier is imposed on the ordinary birth-death processes is considered. An easy-checking criterion for the existence of such Markov processes is first obtained. The uniqueness criterion is then established. In the nonunique case, all the honest processes are explicitly constructed. Ergodicity properties for these processes are investigated. It is proved that honest processes are always ergodic without necessarily imposing any extra conditions. Equilibrium distributions for all these ergodic processes are established. Several examples are provided to illustrate our results.

A reconfigurable component model using reflection

Providing a method of transparent communication and interoperation between distributed software is a requirement for many organisations and several standard and non-standard infrastructures exist for this purpose. Component models do more than just provide a plumbing mechanism for distributed applications, they provide a more controlled interoperation between components. There are very few component models however that have support for advanced dynamic reconfigurability. This paper describes a component model which provides controlled and constrained transparent communication and inter-operation between components in the form of a hierarchical component model. At the same time, the model contains support for advanced run-time reconfigurability of components. The process and benefits of designing a system using the presented model are discussed. A way in which reflective techniques and component frameworks can work together to produce dynamic adaptable systems is explained.

Legal method and legal reflection: experiential learning in the law school

The two main themes of the conference centre around teaching experiences in legal education and theme and international and European perspectives in legal education.

Prediction of reinforcement corrosion in concrete and its effects on concrete cracking and strength reduction

Based on extensive research on reinforcing steel corrosion in concrete in the past decades, it is now possible to estimate the effect of the progression of reinforcement corrosion in concrete infrastructure on its structural performance. There are still areas of considerable uncertainty in the models and in the data available, however This paper uses a recently developed model for reinforcement corrosion in concrete to improve the estimation process and to indicate the practical implications. In particular stochastic models are used to estimate the time likely to elapse for each phase of the whole corrosion process: initiation, corrosion-induced concrete cracking, and structural strength reduction. It was found that, for practical flexural structures subject to chloride attacks, corrosion initiation may start quite early in their service life. It was also found that, once the structure is considered to be unserviceable due to corrosion-induced cracking, there is considerable remaining service life before the structure can be considered to have become unsafe. The procedure proposed in the paper has the potential to serve as a rational tool for practitioners, operators, and asset managers to make decisions about the optimal timing of repairs, strengthening, and/or rehabilitation of corrosion-affected concrete infrastructure. Timely intervention has the potential to prolong the service life of infrastructure.

Fostering 'habits of reflection, independent study and free inquiry': an analysis of the short-lived phenomenon of General/Liberal Studies in English vocational education and training

In 1957, 12 years after the end of World War II, the Ministry of Education issued Circular 323 to promote the development of an element of ‘liberal studies’ in courses offered by technical and further education (FE) colleges in England. This was perceived to be in some ways a peculiar or uncharacteristic development. However, it lasted over 20 years, during which time most students on courses in FE colleges participated in what were termed General or Liberal Studies classes that complemented and/or contrasted with the technical content of their vocational programmes. By the end of the 1970s, these classes had changed in character, moving away from the concept of a ‘liberal education’ towards a prescribed diet of ‘communication studies’. The steady decline in apprenticeship numbers from the late 1960s onwards accelerated in the late 1970s, resulting in a new type of student (the state-funded ‘trainee’) into colleges whose curriculum would be prescribed by the Manpower Services Commission. This paper examines the Ministry’s thinking and charts the rise and fall of a curriculum phenomenon that became immortalised in the ‘Wilt’ novels of Tom Sharpe. The paper argues that the Ministry of Education’s concerns half a century ago are still relevant now, particularly as fresh calls are being made to raise the leaving age from compulsory education to 18, and in light of attempts in England to develop new vocational diplomas for full-time students in schools and colleges.

Reflection is alive and well, but not what you think

More and more, Business and Management students (and those in other disciplines) are being asked to undertake written reflection upon their learning as part of assessed course-work. This paper examines this trend and explores the thinking behind it: why lecturers see reflection as valuable to students, whether they undertake reflection themselves, what theoretical underpinning they perceive as justifying and explaining their views. The results of a survey undertaken among Business and Management lecturers are reported, which appear to show that the most influential writer on the subject of reflection in learning – the one most frequently cited by the respondents – is David A. Kolb, author of the well-known Experiential Learning Theory (1984), and one of the moving forces behind experiential learning in general. His ideas have attracted a good deal of criticism, but are still current, having been suitably updated and defended, (2005). The paper critically re-examines Kolb’s Experiential Learning Theory, challenging its relevance to most of Higher Education, as characterised by Peter Jarvis in his useful table of learning situations as “formal and intended” (2004; 108). Other criticisms of Kolb’s Experiential Learning Theory are advanced that are entirely new. Returning to the survey, the papers discusses the reasons lecturers believe reflection is valuable to students and concludes that Kolb’s model, and others such as Schön’s (1987), fail to adequately explain or even identify them.

Structured reflection breaks embedded in an online course – effects on learning experience, time on task and performance

The purpose of this article is to gain an insight into the effects of practicing short, frequent,and structured reflection breaks interspersed with the learning material in a computer-based course. To that end, the study sets up a standardized control trial with two groups of secondary school pupils. The study shows that while performance is not affected by these embedded “reflection rituals,” they significantly impact time on task and perceived learning. The study also suggests that the exposure to such built-in opportunities for reflection modifies the engagement with the content and fosters the claimed readiness for application of a similar reflective approach to learning in other occasions.