A review of hydrotalcite based catalysts for hydrogen production systems

Hydrotalcite is a double layered lamellar clay and is used as a catalyst precursor due to its structural properties. Hydrotalcite derived catalysts for hydrogen production through different processes have been reviewed. Recent developments of catalysts for hydrogen production are discussed accordingly. A brief introduction to structure and different synthesis routes of hydrotalcite based catalysts is also included. Article is focused on hydrotalcite derived catalysts consisting of different metals like Fe, Ni, Cu, Pt etc. and their performances in hydrogen production at different conditions. Use of such catalysts in hydrogen production process like steam reforming, sorption enhanced based generation, and various other applications is reviewed critically. Pros and cons of catalysts are discussed in detail. The scope and challenges in development of the hydrogen production process have been detailed out focusing modified hydrotalcite derived catalyst and process conditions.     

Whole-body vibration transmissibility in supine humans: Effects of board litter and neck collar

Whole-body vibration has been identified as a stressor to supine patients during medical transportation. The transmissibility between the input platform acceleration and the output acceleration of the head, sternum, pelvis, head-sternum, and pelvis-sternum of eight supine subjects were investigated. Vibration files were utilized in the fore-aft, lateral, and vertical directions. The power spectral density across the bandwidth of 0.5–20 Hz was approximately flat for each file. A comparison between a baseline rigid-support and a support with a long spinal board strapped to a litter has shown that the latter has considerable effects on the transmitted motion in all directions with a double magnification in the vertical direction around 5 Hz. The results also showed that the neck-collar has increased the relative head-sternum flexion–extension because of the input fore-aft vibration, but reduced the head-sternum extension–compression due to the input vertical vibration.     

Regional line of the Cairo metro

Completion of the first phase of the Cairo metro's regional line in 1987 was a milestone for Cairo, which was the first city in Africa and the Middle East to adopt this modern means of transport. The regional metro line serves the Greater Cairo population of 10 million. The line includes 33 stations, five of which are underground stations in the central business disrict, and transports 400,000 passengers per day. The author discusses the project in terms of the site geology of central Cairo, the design concept for the metro, the method of executing the excavation, the interior design of the stations, and the electrical/mechanical works.     

Adaptation fran?aise du "Counseling Evaluation Inventory": une mesure de l'efficacité per?ue de l'aidant.

Tested the factorial stability of a French version of the Counseling Evaluation Inventory by J. Linden et al (1965) and assessed its capacity to differentiate among therapists using different theoretical approaches. 230 university psychology students (aged 19–48 yrs) were asked to evaluate films of 3 counseling sessions by 3 therapists with different theoretical orientations. Ss were divided into separate groups to whom the films were presented in varying orders. The results were statistically analyzed. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress analysis of gear teeth using displacement potential function and finite differences

A new numerical approach has been developed for the analysis of displacements and stresses in arbitrary‐shaped elastic bodies subjected to mixed boundary conditions. An ideal mathematical model, based on the displacement‐potential function, has been used in the finite‐difference solution to investigate the state of stresses at the critical sections of spur gear teeth. Two different types of gear tooth and two different regions of loading are included in the present analysis. The solutions found by the present approach are compared and discussed in the light of available finite‐element results in the literature. Copyright © 2001 John Wiley & Sons, Ltd.     

Electron beam surface modification of a porous bronze-graphite composite

Elemental powders were mixed to obtain a 90 wt pct copper, 8 wt pct tin, and 2 wt pct graphite composite. The porosity level of the sintered specimens was reduced from 25 to 10 pct, which resulted in an increase in the macrohardness value from 17 Hv (90 MPa) to 67 Hv (355 MPa); the density of the sintered specimen was 7.80 g · cm⁻³. The synthesized material was then subjected to electron beam (EB) surface melting. The resultant surface was homogeneous and the microstructural features were refined. The segregation level and variation in the microhardness were drastically reduced. The morphology of the otherwise irregular pores changed to spherical, thereby reducing their interfacial energy. An intriguing modification in the EB melted layer had a density gradient with depth that is sensitive to the heating time of the material using EB. At a heating time of 250 ms, the upper region of the melted layer was dense and hard; the density and the hardness were 8.5 g · cm⁻³ and 103 ± 7 Hv, respectively, while the lower region had density of 6.7 g · cm⁻³ (porosity 22 pct). If the heating time was reduced to 17 ms, the distribution of pores was reversed; the density of upper and lower layers changed to 3.9 and 8.2 g · cm⁻³, respectively. In spite of the higher density of pores, the EB processed composite exhibited increased hardness, compressive strength, and tensile strength. The formation of pores in the lower EB melted region was explained using a qualitative fluid flow model. The combination of a dense substrate and porous surface was desirable, since the former improved the strength and the thermal conductivity of the composite and the latter could be impregnated with oil to achieve the required lubrication levels.     

A study of switching overvoltages on composite feeders—Line-cable feeders

This study is concerned with the overvoltages produced as a result of switching operations on composite feeders, this is when a circuit-breaker closes its contacts at the peak values of the applied voltage. Line-cable feeders are considered in the study. The means by which such overvoltages can be reduced are also included. Also, the effects of system parameters and factors on the initial voltage applied and accompanied overvoltages are covered.     

Mining top?k frequent patterns without minimum support threshold

Finding frequent patterns play an important role in mining association rules, sequences, episodes, Web log mining and many other interesting relationships among data. Frequent pattern mining methods often produce a huge number of frequent itemsets that is not feasible for effective usage. The number of highly correlated patterns is usually very small and may even be one. Most of the existing frequent pattern mining techniques often require the setting of many input parameters and may involve multiple passes over the database. Minimum support is the widely used parameter in frequent pattern mining to discover statistically significant patterns. Specifying appropriate minimum support is a challenging task for a data analyst as the choice of minimum support value is somewhat arbitrary. Generally, it is required to repeatedly execute an algorithm, heuristically tuning the value of minimum support over a wide range, until the desired result is obtained, certainly, a very time-consuming process. Setting up an inappropriate minimum support may also cause an algorithm to fail in finding the true patterns. We present a novel method to efficiently retrieve top few maximal frequent patterns in order of significance without use of the minimum support parameter. Instead, we are only required to specify a more human understandable parameter, namely the desired number itemsets k. Our technique requires only a single pass over the database and generation of length two itemsets. The association ratio graph is proposed as a compact structure containing concise information, which is created in time quadratic to the size of the database. Algorithms are described for using this graph structure to discover top-most and top-k maximal frequent itemsets without minimum support threshold. To effectively achieve this, the method employs construction of an all path source-to-destination tree to discover all maximal cycles in the graph. The results can be ranked in decreasing order of significance. Results are presented demonstrating the performance advantages to be gained from the use of this approach.