Effects of yield to tensile ratio and uniform elongation on the deformability of welded steel frame structures

Abstract

There is a growing tendency to require increased service, beyond the design life, for steel structures such as bridges, vehicles, railways, vessels and construction machinery etc. by the implementation of regular maintenance procedures. During this maintenance products are inspected at relatively short intervals and, based upon the results of inspection and diagnosis, repair and reinforcement work is carried out as the need arises in order to prolong the lifespan. In addition to visual observation, the acoustic tapping method, magnetic powder flaw detection, penetration inspection, ultrasonic flaw detection and the latest measurement apparatus are employed for inspection; however, these conventional flaw detecting methods aim to detect unfavourable conditions, such as defects, cracks, corrosion, deformation, abrasion etc., which are already present within the structure, and are incapable of detecting latent defects and barely valid for fatigue cracks which are likely to occur in the future. Furthermore, after the detection of flaws it may be difficult to carry out corrective maintenance or to put a maintenance expenditure plan in place so the operating plan may fail in the long term.     

Pyrolysis of the mixture of biomass and plastics in countercurrent flow reactor Part I: Experimental analysis and modeling of kinetics

A shaft kiln is considered to be a promising pyrolysis device for the efficient decomposition of municipal wastes. In this device, the temperature distributions of the gas and solid phases can be separately controlled, thereby leading to considerably different profiles for both the phases. The temperature controllability in a shaft kiln helps us to obtain a suitable profile of the gas-phase temperature for the decomposition of tar that evolves from the solid phase. By leveraging this advantage of the shaft kiln, we performed further pyrolysis and steam reforming of the volatiles formed from the pyrolysis of biomass and several polymers using a two-stage reactor that was maintained at different temperatures. The amount of tar decreased with an increase in the temperature in the upper reactor in the absence of a catalyst. By using the experimental results, we developed a lumped kinetic model for secondary gas-phase reactions and performed a kinetic analysis of the reactions that proceeded in the upper reactor. It is confirmed that the simulation model is successful in reproducing the product distribution of the gas-phase reactions of volatiles from biomass and polymers.     

Filtration of Multi-Walled Carbon Nanotube Aerosol by Fibrous Filters

Filtration efficiency of multi-walled carbon nanotube (MWCNT) aerosol by fibrous filter was evaluated experimentally. Mono-mobility test aerosols with electrical mobility diameter of 100, 200, and 300 nm were generated by the atomization of MWCNT aqueous suspension followed by mobility classification with a differential mobility analyzer (DMA). By analyzing the shape of classified aerosol particles under a scanning electron microscope, it was found that the DMA-classified 300 nm particles were fibrous in shape and had uniform diameter of about 60 nm and length of 2.1 micrometer. On the other hand, 100 nm and 200 nm particles contained a fairly large amount of multiply charged fibrous particles with a larger diameter. These test aerosols were challenged to a medium performance fibrous filter at various filtration velocities. As a result, fibrous particles were captured by fibrous filter at a higher collection efficiency than the spherical particles with the same mobility. By analyzing the single fiber capturing efficiency, interception incorporating the rotation of fibrous particles is found to be the dominant capturing mechanism for the fibrous particles in the studied size range.     

Nucleation of Ethylene Glycol Vapor and Growth of Sub-10-nm Particles in Nanoparticle Size Magnifier

We investigated the rates of heterogeneous and homogeneous nucleation of ethylene glycol vapor onto sub-10-nm particles in a newly developed condensation device called nanoparticle size magnifier (NanoPSM). The saturation ratio in the NanoPSM is precisely controlled by vapor-feeding system and mixing section, which are designed based on an earlier particle size magnifier (PSM) developed by Okuyama et al. (1984). Size-classified NaCl nanoparticles smaller than 10 nm in mobility diameter are used as heterogeneous nuclei for the condensation of ethylene glycol vapor. The activation efficiency and growth rate of the activated nuclei are determined by a pulse height analysis using an optical particle counter (OPC). A computer fluid dynamics (CFD) simulation is employed to calculate the profiles of the gas velocity, temperature, vapor concentration, and resulting supersaturation in the NanoPSM. Annular high-supersaturation region is generated around the mixing boundary between cold aerosol and hot vapor. The experimental activation efficiency is 50% for 4.5-nm and 0.8% for 2 nm NaCl particles, through the subsequent growth of droplets to 2 μm in diameter. The experimental data are in fairly good agreement with the predicted activation efficiencies based on the classical Kelvin-Thomson theory when the local profiles of supersaturation are taken into account.     

Modulation of Spin-Crossover Behavior in an Elongated and Flexible Hofmann-Type Porous Coordination Polymer

Three porous coordination polymers {Fe(dpa)[Pt(CN)₄]·G·nH₂O} (1-G; dpa = 1,2-di(4-pyridyl)ethane, G = dpa, bibenzyl (bbz) and stilbene (stb)) have been prepared by using a long and flexible ligand dpa. These compounds formed analogous 3-D elongated Hofmann-type frameworks based on 2-D planar layers extended by Pt–CN–Fe linkages with dpa as flexible pillar ligands. 1-dpa showed a characteristic three-step spin transition (ST) in the temperature range 180–240 K. The ST behavior was reversibly modulated by dehydration and hydration processes in keeping with the three steps. 1-bbz and 1-stb exhibited a gradual three-step ST over the range 80–200 K and an abrupt ST with T _c = 163 K. The guest-dependent cooperativity of the ST behavior is discussed by considering the flexibility of the framework and guest molecules.     

Spark Plasma Sintering of Sol–Gel Derived Amorphous ZrW2O8 Nanopowder

Dense ZrW₂O₈ was prepared by spark plasma sintering (SPS), using amorphous ZrW₂O₈ nanopowder as a raw material, at 873 K for 10 min. We investigated the effects of SPS conditions, such as sintering temperature, heating rate, and the discharge power that is expressed as the product of pulsed direct current and voltage, on the densification process of ZrW₂O₈. The relative density and microstructure of ZrW₂O₈ prepared by SPS were compared with those of ZrW₂O₈ prepared by hot pressing (HP). The relative density of ZrW₂O₈ prepared by HP at 873 K for 1 h was 63.1%. On the contrary, the relative density of ZrW₂O₈ prepared by SPS at 873 K for 10 min at a heating rate of 50 K/min was 98.6%. These results show that the discharge pressure that is proportional to discharge power enhances the densification and grain growth of ZrW₂O₈ in the SPS process.     

Jacqueline C. Bouhoutsos (1924–2008).

Jacqueline C. Bouhoutsos died in Los Angeles on May 22, 2008, at the age of 83, after a prolonged and severely disabling struggle with Alzheimer’s disease. She was a trailblazing psychologist who had an important impact not only on the discipline but also on the public through innovative research, legislative advocacy, media psychology, and forensic psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biohydrogen production by anaerobic co-digestion of municipal food waste and sewage sludges

Food waste (FW), primary sludge (PS) and waste activated sludge (WAS) were characterized and found to be complementary in the concentrations of carbohydrates, total Kjeldahl nitrogen (TKN), PO₄–P and some metal for biological hydrogen production. Moreover, FW was found to have low pH buffering capacity while the values for PS and WAS were relatively higher. An anaerobic toxicity analysis (ATA) derived from a methanogenic ATA protocol showed that these waste materials had no toxicity to hydrogen production. Adding phosphate buffer to the FW significantly improved hydrogen production while initial pH was 7.0. Co-digestion of FW and sewage sludge was studied using a batch respirometric cultivation system. All combinations of the feedstocks (FW+PS, FW+WAS and FW+PS+WAS) showed enhanced hydrogen production potential as compared with the individual wastes. A mixing ratio of 1:1 was found to be the best among the ratios tested for all three co-digestion groups. A hydrogen yield of 112 mL/g volatile solid (VS) added was obtained from a combination of FW, PS and WAS. This yield was equivalent to 250 mL/g VS added if only FW contributed to hydrogen production. The reason for the enhancement of hydrogen production was postulated to be multifold in which the increase in buffer capacity in the co-digestion mixture was verified.     

Production of an iron-loaded carbonaceous material through pyrolyzing biomass impregnated with FeCl2

We propose a novel method for preparing iron-dispersed carbonaceous materials by utilizing low-grade materials and waste heat. Iron is loaded into the biomass through stirring it in a solution of FeCl₂ for 2 h and then pyrolyzed at 600–900 °C to prepare materials composed of iron and carbon. Further in order to investigate the reactivity of the sample, steam and CO₂ gasifications of the material was performed at 800–900 °C. Approximately 80% of the carbon in the biomass remained in the solid state during pyrolysis at 600 °C because of the effect of FeCl₂ in promoting the carbonization of the biomass. The prepared material displayed high reactivity during gasification due to the catalytic effect of loaded iron. This result indicated the possibility that the composite may be used as an iron and heat source for a steel converter. Furthermore, the high reactivity of the composite during steam gasification suggests its usefulness as a medium for hydrogen or carbon monoxide production.