Remarkable enhancement in durability of Pd/H-ZSM-5 zeolite catalysts for CH4-SCR

Effect of second components on the catalytic performance of Pd/H-ZSM-5 zeolite (Pd: 0.4 wt.%) was evaluated by a durability test of NO reduction with CH₄ at a relatively high temperature of 500°C in the presence of water vapor for a prolonged period. The Pd/H-ZSM-5 showed high stable activity for this reaction without H₂O in the reactant feed, while immediate and irreversible deactivation was observed in the presence of H₂O, resulting in no activity after 7 h. The second components such as Co, Rh, Ag, Ce, and Fe introduced individually to the Pd/H-ZSM-5 enhanced the durability, and in particular the addition of 3.3 wt.% Co led to a stable NO conversion for more than 40 h in the presence of H₂O.     

High-temperature deformation and fracture behaviour of Cu-SiO2 bicrystals

Bicrystals of CU-SiO₂ dispersion-hardened alloys and of pure copper were tensile tested at various temperatures between 450 and 1050 K at a strain rate of 1.5 x 10^–4 sec^–1. In the case of pure copper bicrystals, elongation to fracture did not depend significantly on temperature and the fracture mode was invariably transgranular up to 850 K. On the other hand, the ductility of CU-SiO₂ bicrystals decreased with increase in temperature and the transition in the fracture mode from transgranular to intergranular occurred at around 450 K. SiO₂ particles on grain boundaries play an important role on intergranular fracture by suppressing grain-boundary sliding and also on the retardation of recrystallization during deformation. Two types of Cu-SiO₂ bicrystals having different crystal orientation relationships show quite different deformation and fracture behaviour. This can be explained in terms of the contribution of lattice dislocations to the grain-boundary sliding.     

The structure of the core polyol of the ether lipids fromSulfolobus acidocaldarius

The major ether-type lipid structures ofSulfolobus acidocaldarius (ATCC33909) were composed of caldarchaeol and calditoglycerocaldarchaeol. However, the characterization by nuclear magnetic resonance spectroscopy and mass spectrometry showed that the structure of calditol in calditoglycerocaldarchaeol is not nonitol, 2-(1′,2′,3′-trihydroxypropyl)1,2,3,4,5,6-hexahydroxyhexane, but 2-hydroxymethyl-1-(2,3-dihydroxypropoxy),2,3,4,5-cyclopentanetetraol with an ether linkage in the molecule. Such an intermolecular ether linkage was resistant, to BCl₃ treatment, but nonresistant to 57% HI degradation treatment conducted at 100°C for 60 h, producting 2-hydroxymethyl-1,2,3,4,5-cyclopentanepentaol from calditol as reaction product. Further, it was confirmed that the structure of calditol is essentially a derivative of glycerol, and hydrocarbon chains were conjugated to the glycerol-like site in the structure. The calditol with an ether linkage in the molecule suggested an important role regarding the properties of heat-resistance and acid-resistance observed inSulfolobales. Presented at the international workshop on “Molecular Biology and Biotechnology of Extremophiles and Archaebacteria,” Wako, Japan, August 1993.     

Development of incremental deep drawing process

This paper deals with development of an incremental deep drawing process. On a newly developed incremental deep drawing set-up, the aluminium sheets are formed; the forming is carried out by deep-drawing the blank as in the conventional method but incrementally. Fractures at the punch or die corner in the blank may or may not occur depending on the conditions; the process parameters involved are punch size, punch corner radius, increment in punch displacement, blank holding force or pressure, etc. It is thus shown that different shapes are formed by one set of common tools. It is thereby confirmed that incremental deep drawing is possible without using a particular tool set for a particular shape.     

Negative Pore Air Pressure Generation in Backfill of Retaining Walls During Earthquakes and its Effect on Seismic Earth Pressure

In order to investigate the seismic behavior of conventional type and geosynthetic-reinforced soil retaining walls, 1-g model shaking tests were conducted. Model walls having a height of about 50 cm were placed on a subsoil layer and backfilled with a layer of dense dry Toyoura sand. They were subjected to several steps of horizontal irregular excitations. As a result, generation of negative pore air pressure in the backfill was observed. The maximum amplitude of the negative pore air pressure during each shaking step increased with the base acceleration. Based on analyses of the measured data, it was inferred that such negative pore air pressure was caused by outward wall displacement relative to the backfill and not by dilative behavior of the backfill. It would cause a reduction in the seismic earth pressures exerted from the backfill. This feature suggests an advantage of a rigid full-height facing for reinforced soil walls over the segmental types of facing. A simplified numerical procedure to evaluate earth pressure was applied while considering the effects of the negative pore air pressure, and it could qualitatively simulate the measured behavior in terms of the seismic earth pressure and the angle of failure plane in the backfill.     

Applicability of the generalized scaling law to a pile-inclined ground system subject to liquefaction-induced lateral spreading

The generalized scaling law is based on the concept of two-stage scaling and allows currently available centrifuge facilities to model a large-scale prototype expanding over the spatial dimension ranging from 30 m or larger subject to earthquake motions. This paper presents the results of investigation on the applicability of the generalized scaling law to the fully nonlinear regime of soil-structure system with the induced strain level of 10% in the order of magnitude. The centrifuge model tests performed in this study under the modeling of models scheme consist of a pile model embedded in a inclined ground subject to liquefaction-induced lateral spreading. Four different centrifugal accelerations ranging from 13g to 50g are used whereas the actual size of the physical model is kept constant with an overall scaling factor of 1/100. The models are exposed to tapered sinusoidal input accelerations of frequency 0.59 Hz and amplitude 3.0 m/s² in prototype scale, and the results are compared in terms of prototype by applying the generalized scaling law. As for the response of the ground during shaking, essentially identical accelerations and excess pore water pressures are recorded for all cases, while the lateral displacement shows a variation ranging from 5% to 9% in terms of shear strain due to a slight variation in experimental conditions (e.g., input peak acceleration, achieved density distribution). Practically the same responses are measured among the cases in the dissipation phase of excess pore water pressure. With regard to pile behavior, nearly identical responses for the lateral displacements and bending moments are obtained for all cases both during and after shaking. These results demonstrated that the generalized scaling law is applicable to the fully nonlinear regime of soil-structure system subject to the cumulative shear strain in the order of 10% due to cyclic mobility of sands during earthquakes.     

Performance of plastic gear made of carbon fiber reinforced poly-ether-ether-ketone: Part 2

Five kinds of PEEK/CF composites, made by blending poly-ether-ether-ketone (PEEK) with three kinds of PAN type carbon fibers (CFs) and two kinds of pitch type CFs respectively, were injection-molded into gears. Their gear performance such as the load capability and the wear of tooth were evaluated. The wear properties of PEEK/CF gears extremely varied depending on the kinds of CFs, when the same type gears were combined and grease was initially applied. Also, the load capabilities were significantly influenced by the affinity between PEEK and CF. A composite gear reinforced with CF of the highest density indicated the highest load capability irrespective of the test conditions, due to the lowest abrasive property of the CF as well as the excellent affinity between PEEK and CF. Its load capability under a high temperature running condition was found to be superior to that of polyamideimide (PAI) composite gear or polyphenylenesulphide (PPS) composite gear.     

Construction and field measurement of high-speed railway test embankment built on Indian expansive soil “Black Cotton Soil”

The railway embankment applied to high-speed railways is required to have high performance in terms of strength and deformation characteristics. Especially in the case of railway embankments that support slab tracks, the allowable settlement is very small. There are two technical challenges in constructing high-speed rail embankments to support slab tracks in India. The first challenge is dealing with problematic black cotton soil (BCS), which is widely distributed in India but very unusual soil in Japan. The second challenge is posed by the strict deformation requirement in the construction of the embankments. In this study, a 6 m-high test embankment was constructed on BCS in India. The deformation of the embankment and changes in water content were measured over a period of 18 months. In the construction of the test embankment, two different BCS countermeasures were applied. The results of the tests on this embankment were compared with those from an embankment without countermeasures. Complicated deformation behaviors, including settlement and the uplift of embankment, were observed in the section without countermeasure. However, in the embankment with cement-mixed gravelly soil (CGS) slab improvement with geosynthetics, the much lower amplitude of embankment deformation is evidence of the effectiveness of this countermeasure. The cohesive non-swelling soil (CNS) layer applied immediately below the embankment to reduce the water content fluctuation of BCS was not effective enough for use for high-speed railway embankment. Besides determining the technical challenges for the BCS countermeasures, the results of this study confirmed that a high-performance embankment can be constructed with Indian embankment material by performing sufficient compaction management.     

Shear behaviour of reinforced concrete structural walls with eccentric openings under cyclic loading: experimental study

Reinforced concrete (RC) structural walls usually have some eccentric large openings according to the intention of the architectural design. However, the behaviour of such structures that are shear critical under cyclic loading has not been well studied. In this study, three single‐span, three‐storied, 40% scale specimens of RC structural walls with various eccentric opening ratios were constructed and tested in a lateral reverse cyclic manner until severe shear damage occurred in the walls. The main purposes of these tests were to evaluate the shear behaviour and to recognize the influence of various opening ratios on cracking and shear strength of structural walls under cyclic loading. The shear strength of specimen was calculated combining the shear strength of a structural wall without openings and the reduction factor due to openings. The comparison between the experimental results and the analytical results shows that the shear strength is different depending on the loading direction due to the eccentric opening location, the span length of short span beams may affect the cracking process and the failure mode, the approximate calculation method using Ono's reduction factor could be well applied to RC structural walls with various opening ratios less than 0.46. Copyright © 2010 John Wiley & Sons, Ltd.     

Disinfection of Legionella pneumophila by ultrasonic treatment with TiO2

An ultrasonic treatment system, using a TiO₂ photocatalyst, was used to disinfect Legionella pneumophila. A kinetic study of the process indicates that TiO₂ significantly improves the disinfection process. The concentrations of viable cells were reduced to 6% of the initial concentrations in the presence of 0.2 g/ml TiO₂ after a 30 min of treatment period, while only an 18% reduction was observed in the absence of TiO₂. The potency of the disinfection could be enhanced, to some extent, by increasing the amount of TiO₂ used. Cell concentrations were decreased by an order of 3 within 30 min of treatment in the presence of 1.0 g/ml TiO₂. The disinfection power in the presence of TiO₂ versus Al₂O₃ was also compared and the findings showed that TiO₂ induced a higher cell killing. No significant effect of initial cell concentration on the disinfection was found in the range of 10²-10⁷ CFU/ml after a 30 min of treatment period. The mechanism of cell killing was investigated by examining the effects of OH radical scavengers such as ascorbic acid, histidine and glutathione. The disinfection power was reduced in samples that contained these radical scavengers, thus indicating the importance of OH radicals.