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Diffusion limitations inducing pores blocking is a key para- meter when using heterogeneous catalysts. The aim of this work is to study the influence of the particle size and therefore, the external surface extent, on catalytic properties of ZSM-5 crystals. Nanocrystals or microcrystals of Cu-ZSM-5 were prepared and characterized. The key difference between these catalysts is the extent of external active surface, favouring the nanocrystal form of ZSM-5. Both materials were further employed for the catalytic oxidation of various substrates differing by their size. Oxidation of indane, tetralin, propyl and octylbenzene was successfully performed when using both catalysts. However, a clear enhancement was observed when the nanocrystal form of Cu-ZSM-5 was used. The different efficiency of both catalysts was discussed in terms of external active surface and diffusion limitations.

Diffusion limitations inducing pores blocking is a key para- meter when using heterogeneous catalysts. The aim of this work is to study the influence of the particle size and therefore, the external surface extent, on catalytic properties of ZSM-5 crystals. Nanocrystals or microcrystals of Cu-ZSM-5 were prepared and characterized. The key difference between these catalysts is the extent of external active surface, favouring the nanocrystal form of ZSM-5. Both materials were further employed for the catalytic oxidation of various substrates differing by their size. Oxidation of indane, tetralin, propyl and octylbenzene was successfully performed when using both catalysts. However, a clear enhancement was observed when the nanocrystal form of Cu-ZSM-5 was used. The different efficiency of both catalysts was discussed in terms of external active surface and diffusion limitations.

Earlier studies on the design of reinforced concrete structures by equilibriumserviceability methods (that simultaneously satisfy collapse and service criteria) are extended to continuous prestressed and partially prestressed concrete structures. The objectives of the paper are to present a practical design approach to nonlinear design for prestressed concrete structures and to identify its potential benefits. The paper also demonstrates the conflict between desirable plastic redistribution (at ultimate limit state) and zero or limited cracking (at serviceability limit state) for fully prestressed concrete structures. Optimization results suggest that partially prestressed concrete structures represent the most economical compromise between these conflicting criteria, and the optimal prestressing degree strikes a good balance between adequate service conditions (stresses, cracking, and deflection) and economy. Optimization of prestressed concrete beams is cast as a nonlinear programming problem and is solved by the projected Lagrangian algorithm. Examples of (threespan and twospan) continuousbeam optimizations illustrate the method and its features, as well as resulting differences between full and partial prestressing design solutions.

This paper presents a practical and efficient approach to the optimization of prestressed concrete structures if two or more (possibly conflicting) objectives must simultaneously be satisfied. The most relevant objective function is adopted as the primary criterion, and the other objective functions are transformed into constraints by imposing some lower and upper bounds on them. The singleobjective optimization problem is then solved by the projected Lagrangian algorithm. Two numerical examples illustrate the application of the approach to the design of a posttensioned floor slab and a pretensioned highway bridge system for two conflicting objectives: minimum cost and minimum initial camber. The Pareto optima achieve a compromise between the two conflicting objectives and represent more rational solutions than those obtained by independent optimizing each objective function.

Superstructure design of short and mediumspan highway bridge systems may be conceived as a process of multilevel and multiobjective optimization. Three optimization levels are identified: (1) Level 1—component optimization; (2) level 2—structural configuration optimization; and (3) level 3—overall system optimization. Designs may be optimized by separately or simultaneously considering one, two, or more of the following objectives: cost, prestressing steel or concrete consumption, and superstructure depth. The optimal solution may be found by a sequence of nonlinear programming and sievesearch techniques. Levels 1 and 2 optimizations identify the best solutions for specific components (precast Igirders, voided and solid slabs, single and twocell box girders) and layouts (for precast Igirder: one, two, and three; simple or continuous spans). Level 3 optimization selects the overall best system for given bridge lengths, widths, and traffic loadings. The present study results in: (1) A systematic procedure for bridge design; (2) a rational approach to optimization of standard precast sections; (3) direct design aids for selection of optimized bridge systems; and (4) simplified optimality criteria for preliminary design.

We give the great interest to characterise the InP and InPO4/InP submitted to electron beam irradiation owing to the Auger Electron Spectroscopy (AES) associated to both methods Electron Energy Loss Spectroscopy (EELS). The incident electron produces breaking of (In-P) chemical bonds. The electron beam even acts to stimulate oxidation of InP surface involving on the top layers. Other, the oxide InPO4 developed on InP does appear very sensitive to the irradiation due to electron beam shown by the monitoring of EELS spectra recorded versus the irradiated times of the surface. There appears a new oxide thought to be In2O3. We give the simulation methods Casino (Carlo simulation of electron trajectory in solids) for determination with accuracy the loss energy of backscattered electrons and compared with reports results have been obtained with EELS Spectroscopy. These techniques of spectroscopy alone do not be able to verify the affected depth during interaction process. So, using this simulation method, we determine the interaction of electrons in the matter.

The use of polycarbonate bottles as track detectors makes it possible to overcome some of the shortcomings of the electrochemically etched dosemeters such as the complexity of the etching apparatus, the strong angular dependence, and the difficulty of measuring the neutron incident angle. Because of its shape, the bottle provides a dosemeter with isotropic response and separates electrically the two etching electrolytes, as required for the electrochemical etching processes. Since the polycarbonate bottles are used typically as containers of bubble detectors, a detector combination is thus achieved, which can be used to good advantage to solve the complex problem of personal neutron monitoring.

The Dosimetry Laboratory of the Radiation Protection and Safety Centre in Algiers has developed a fast neutron personal dosemeter using a PADC detector. This dosemeter has been type tested in terms of the ICRU calibration quantity, directional dose equivalent at 10 mm, H'(10). This paper gives the results of type test measurements. In addition, some properties of five different PADC materials were investigated in this study.