Design considerations and experimental studies on semi-active smart pin joint

Hostile dynamic loadings such as severe wind storms, earthquakes, and sudden impacts can cause severe damage to many civil engineering structures. An intelligent structural system equipped with smart structural members that are controllable in real-time is an effective solution to structural damage and failure during such situations. Civil intelligent structures with controllable properties to adapt to any changes due to dynamic loadings can lead to effective protection of structures and their occupants. In this paper, design and testing of a semi-active magnetorheological (MR) pin joint, in which the moment resistance can be controlled in real-time by altering the magnetic field, is reported with the view of using it as a potential candidate for smart members in the development of intelligent structures. Design of prototype smart pin joints includes theoretical analysis related to the radius of the rotary plate, the property of MR fluids and the gap between the rotary plate and the casing based on the requirements of the dynamics of MR pin joints. FEM analysis was deployed to study the distribution of the magnetic field along the gap. It is found, from the theoretical analysis and experimental verification, that the MR pin joint with a diameter of 180 mm can produce a torque of up to 30 Nm, which meets requirements for semi-active members in a multi-storey prototype building model in the next stage of research and development.     

Influence of seismic incident angle on response uncertainty and structural performance of tall asymmetric structure

The estimation of critical seismic response of a structure is complicated in nature due to the uncertain distribution of the internal forces under multidirectional seismic excitations. One of the important concerns inherent to this complication is the uncertainty associated with the final design direction as different seismic directions result in different seismic responses. In this regard, this research provides a detailed examination of (1) response‐to‐response and record‐to‐record variability under varying seismic orientations, (2) quantification of seismic response uncertainties and (3) the seismic performance of asymmetric structure in the context of conservative/nonconservative seismic design. With the mentioned research objectives, a realistic case study asymmetric structure under the influence of varying bidirectional seismic excitations was evaluated. It has been argued in this research that the seismic excitations applied at structure's reference axes are very unlikely to demonstrate maximum response for all response quantities simultaneously, even if it results in a peak response for a particular seismic response quantity. This research is particularly helpful for the critical assessment of directionality influence on asymmetric structures prior to making any decision during thestructural design process. Substantial arguments have been presented to emphasize the inclusion of the investigation of seismic response uncertainty in practical design of critical asymmetric structures.     

Reliability analysis of the flat-topped array beam FSO communication link

Free-space optical communication systems are affected by turbulent atmosphere. The atmospheric transmission is affected by absorption, scattering and turbulence. In this paper, the effects of absorption and scattering are taken into account using Beer’s law and the effects of turbulence are considered in calculating the average intensity distribution. An analytical expression for the average intensity distribution of a partially coherent flat-topped array (PCFTA) beam in turbulent atmosphere is derived based on the extended Huygens–Fresnel principle. The average intensity, power in bucket, signal to noise ratio, and bit error rate of this kind of beam are investigated in details. It is shown by numerical results and analytical methods that the average intensity and link parameters of PCFTA beams change during propagation and these changes are dependent upon both source parameters and weather conditions.     

Thermal and crystallization behavior of SiO2-PbF2 glass system in the presence of ErF3 and Al2O3

Oxyfluoride glass-ceramics have been introduced as one of the best bulk hosts for upconversion process of rare-earth ions. However, less attention to the technological topics in the process of glass crystallization has hindered the development of them in industrial scale applications. In this research, SiO₂–PbF₂ glasses were investigated to clarify the ambiguous role of rare-earth ions and alumina content in the microstructure and crystallization behavior. Results indicated that Er³⁺ addition caused a liquid-liquid phase separation via nucleation and growth mechanism, which led to single phase crystallization of β-PbF₂:Er³⁺ solid solution. Moreover, Er³⁺ had a significant effect on the crystallite size, size distribution, and PbF₂ crystallization temperature. On the other hand, increasing Al₂O₃ content enhanced the transparency and thermal stability of glass samples, whereas it reduced the amount of fluorine loss and increased the dissolution of Er³⁺ in fluoride crystalline structure. These results address some of the most controversial issues about crystallization behavior of rare-earth-doped oxyfluoride glasses.     

Making a Robust Interfacial Scaffold: Bijel Rheology and its Link to Processability

Confocal microscopy and rheology studies of two bijel systems are presented to elucidate relationships between the physicochemical properties of bijels and their ability to be utilized as soft matter templates for materials synthesis. For the first time, the origins of viscoelasticity in these systems are investigated using conventional rheometry and a direct correspondence between the elastic storage modulus, particle loading, and the departure from criticality is observed. Further, the rheological transitions that accompany fluid re‐mixing in bijels are characterized, providing key insights into the synergistic role of interfacial tension and interparticle interactions in mediating their mechanical robustness. Bijels that are predominantly stabilized by interfacial tension are also highly sensitive to gradients in chemical composition and more easily prone to mechanical failure during processing. Despite this increased sensitivity, a modified strategy for processing these more delicate systems is developed and its efficacy is demonstrated by synthesizing a bicontinuous macroporous hydrogel scaffold.     

Dendrosomes as novel gene porters‐III

BACKGROUND: It was previously reported that dendrosomes, i.e. neutral, biodegradable, covalent or self‐assembled, hyperbranched, spheroidal nano‐particles with a size ranging from 15 to 100 nm, provide a convenient and efficient means of gene delivery into various kinds of cells such as human hepatoma and kidney cells as well as animal models. RESULTS: New studies via circular dichroism show that hydrophilic and amphipathic dendrosomes either do not affect the DNA structure or moderately transform it from B‐ to A‐conformation. Gene delivery into human liver, kidney, and endothelial cells as well as other animal cells like Bowes, U‐937, Raw, CCRF‐CEM, MOLT‐4, K562, Huh‐7 and VERO reveal that the genes are efficiently expressed and in comparison with other gene porters like Lipofectin or bacterial ghosts, do quite well. It is also shown that dendrosomes are able to deliver genes into cells like endothelials that are usually hard to transfect. Cell culture experiments as well as intraperitoneal/intradermal injections of dendrosomes into mice establish their nontoxicity (up to 2.5 mg kg^?1 of animal weight in the latter case). Studies on immunization of BALB/c mice using conventional adjuvants such as aluminium phosphate, C_pG motif and one of the dendrosomes, indicate that the latter leads to the mildest initial response development while exceeding them afterwards. CONCLUSION: CD studies reveal that, owing to the neutrality of dendrosomes, formation of Den/DNA complexes is accompanied by slight structural modifications of DNA cell culture, and animal studies reveal that dendrosomes are inert, non‐toxic and highly efficient gene porters that perform at extremely low doses. In comparison with bacterial ghosts and some common porters, they are efficient in delivery of genes into animals and a variety of cells including those that are usually hard to transfect. Copyright © 2008 Society of Chemical Industry     

Using ozone to reduce recalcitrant compounds and to enhance biodegradability of pulp and paper effluents.

The effect of ozone based oxidation on removing recalcitrant organic matter (ROM) and enhancing the biodegradability of alkaline bleach plant effluent was investigated. A bubble column ozonation tower was used in the study. The experiments were carried out at different temperatures (20 degrees C and 60 degrees C) and pH (9 and 11), with a number of biological and chemical parameters being monitored including BOD5, COD, TC, pH, color, and molecular weight distribution of organics (nominal cut off of 1,000 Da). Biodegradability of the effluent was determined based on BOD5/COD of the wastewater throughout the process. For all the experiments, ozonation enhanced the biodegradability of the effluent by 30-40%, which was associated with noticeable removal of ROM including high molecular weight (HMW) and color-causing organics by about 30% and 60%, respectively. While the biodegradability of HMW fraction increased by about 50%, there was no biodegradability improvement for low molecular weight (LMW) portion, which was originally readily biodegradable (with BOD5/COD of about 0.5). Statistical analysis of variance (ANOVA) revealed neither pH nor temperature played significant role on the ozonation process at 95% confidence level.     

Low-temperature synthesis of bioactive glass-ceramic microspheres: Effect of processing parameters on the size and morphology

A low-temperature method was developed to produce bioactive glass microspheres (BGMs). The microspheres were fabricated by dispersing the prepared sol in silicon oil, a process called the sol-microemulsion-gel method. The resulting microspheres were characterized by X-ray diffractometry (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Brunauer-Emmett-Teller (BET) techniques. Furthermore, the effect of various processing parameters such as reaction chamber size and the stirring rate on microspheres diameter was investigated. The results indicated that under optimized conditions, one could obtain BGMs with acceptable sphericity having a narrow size distribution. The obtained microspheres had diameters in the range of 19.3 ± 9.3 μm. The BET specific surface area was 240.33 m²/g. The results also showed that the increase in the reaction chamber size had interesting contradictory effects on BGMs diameter. The increase in the stirring rate intensified the shear forces exerted on the water-based phase and caused the generation of smaller droplets and microspheres.     

Iran's nuclear power programme revisited

Iran's new government has not yet made a final decision about the fate of that country's once ambitious nuclear power programme. If the programme is kept alive, it will be limited to the completion of at most one or two of the reactors that were already well underway when the revolution broke out. The author traces the origins and growth of the Iranian nuclear power programme between 1974 and 1978, summarizes the principal economic, infrastructural, and political criticisms of the programme as originally planned, discusses the potential for greater use of natural gas as an alternative and, finally, recommends a long, detailed reassessment of Iran's energy options.