A simple two-way coupling method of BEM and VOF model for random wave calculations

A numerical method, which combines the boundary element method (BEM) and the volume of the fluid method (VOF method), has been presented to solve wave–structure interactions; the intense wave motion at the proximity of the structure is modeled by the VOF method and the rest of the fluid region is modeled by the BEM. The combined method can considerably reduce the time-consuming VOF domain, and thus practically makes it possible to apply the VOF method for random wave calculations, in which long time computations are usually required to obtain statistically meaningful results, and therefore the use of the single-VOF model often becomes prohibitive in terms of computational time and storage memories. A VOF model CADMAS-SURF, which is based on SMAC scheme and had been constructed by a number of VOF researchers in coastal engineering in Japan, is used in the combined BEM–VOF model. The two-way coupling treatment, which enables us to deal with bidirectional wave propagations, which was originally given for the SOLA-VOF model by Yan et al. (2003a) and later improved by Kim et al. (2007), was modified for the SMAC scheme. The coupling treatments are described in detail in the paper. The validity of the combined BEM–VOF model was investigated by comparing the numerical results with the theoretical results for the propagations of Stokes 5th order waves and random waves.     

Financial risk management for energy service project under the Tokyo emission trading system

Recently, energy service providers (ESP) have increased due to deregulation in the power market. They install energy supply equipment at their own cost and supply the necessary energy to the client. The Tokyo Metropolitan Government started Asia’s first cap-and-trade program in April 2010. This program caps energy-related carbon dioxide emissions from some 1,330 offices and factories in Tokyo. Then, ESPs have to manage the many risks of energy service project directly linked to the profits. In this paper, we describes the risk analysis and investment optimization for energy service projects using financial engineering.     

Secondary instability and three-dimensionalization in a laboratory accelerating shear layer with varying density differences

We investigate the processes by which an accelerating stratified shear flow undergoes the transition to turbulence in a sequence of experiments in a tilted tank. We observe that the processes by which the flow undergoes breakdown are both complex and diverse, and suggest that the ratio, D, of the depth of the shear layer to the total tank depth and/or the (nondimensional) total density difference are important parameters in the determination of the dominant structures. In general, inherently three-dimensional, and relatively large-scale, flow structures strongly suppress simple subharmonic vortex pairing, and appear to dominate totally the transition to turbulence. In certain circumstances, the primary instabilities of the flow, namely Kelvin-Helmholtz billows, are able to develop in a quasi-two-dimensional manner before interaction between neighbouring billows becomes significant. In these circumstances, narrow secondary streamwise ‘tubes’ of vorticity are observed between neighbouring billows. Alternatively subharmonic, quasi-two-dimensional vortex mergings may be observed; these are not just simple pairings, but also three vortices are observed to merge into a single secondary billow, or two merge and the other persists, as predicted theoretically by Klaassen and Peltier (J. Fluid Mech., 202: 367–402, 1989). Three-dimensional vortex merging (knotting) of initially quasi-two-dimensional billows is also observed. Such knots are observed not only as pairwise transitions, as discussed by Thorpe (Geophys. Astrophys. Fluid Dyn., 34: 175–199, 1985), but also single billows are observed to knot with both adjacent neighbours simultaneously. Also, billows are observed to bow during merging events. However, particularly at larger density differences, higher Reynolds number and when the depth ratio, D, is sufficiently small, billow-billow interactions are apparent essentially immediately upon instability onset. Although the structures which develop resemble secondary tubes, these structures appear to be a primary instability of the flow, analogous to an instability observed by other researchers in both forced and unforced homogeneous shear layers.     

Mussel watch of PCBs and persistent pesticide residues in Perna viridis Linnaeus from Malaysian and Singapore waters

Mussel watch pollution monitoring programmes, performed at six predetermined stations on the Island of Penang, Malaysia, showed that levels of the pollutant pp′-DDE ranged between 3·7 and 17·4 ppb, while PCBs ranged between 99·9 and 599·9 ppb on a dry weight basis. Similar studies on samples from three stations in the Republic of Singapore varied from 7·11 to 8·12 and 139·8 to 256·4 ppb, respectively, for pp′-DDE and PCBs.The study further indicated that other organic chlorinated hydrocarbons were not detectable in this marine bivalve at either locality. Their absence in this instance could be a feature of the tropics, resulting perhaps from a high rate of degradation, purification or a geographical separation between the source of the pollution and the population investigated.     

Characterization of serpentinization in olivine-orthopyroxene-H2O system revealed by thermogravimetric and multivariate statistical analyses

Thermogravimetric (TG) analyses were used to characterize the products and quantify the extent of serpentinization as a stepwise weight loss during heating (TG loss) or its derivative (DTG). Multivariate analyses are powerful tools for extracting information from complicated spectrum data; however, no studies have applied them to characterize serpentinites. In this study, hydrothermal experiments of olivine-H₂O, olivine–orthopyroxene-H₂O and orthopyroxene-H₂O were conducted at 250–400°C and under vapor-saturated pressure. The product minerals observed were serpentine+brucite+magnetite in the olivine-H₂O experiments and serpentine±talc in the orthoyroxene-H₂O and olivine-orthopyroxene-H₂O experiments. These results are consistent with those of previous studies; however, the positions and width of DTG peaks for individual minerals were varied depending on the experimental conditions. To extract systematics from the TG spectra, non-negative matrix factorization (NMF), an unsupervised machine learning technique, was applied to the DTG spectra of the experimental products. NMF revealed that the DTG profiles were explained by a linear combination of six basis spectra, which corresponded to the characteristic products, including three types of serpentine minerals (low-, medium-, and high-T), two types of brucite (low-and high-T), two type of talc (talc+serpentine mixture, well-crystallized talc) with different crystallinity, and noise during the TG measurement. Systematic changes in the factor loading revealed that, in the olivine-H₂O systems, the products changed from medium-T serpentine+low-T brucite to high-T serpentine+high-T brucite as serpentinization progressed. In the olivine-orthopyroxene system, low-T serpentine or poorly crystallized talc+serpentine mixture was initially formed, followed by the formation of well-crystallized talc, resulting in dehydration. Applying NMF to DTG showed the mineralogical differences between olivine and orthopyroxene systems and increases of the crystallinity during the progress of serpentinization, suggesting its potential for characterizing various serpentinites within oceanic lithospheres that suffer from several stages of alteration and weathering at different temperatures.     

Magma plumbing system beneath Ontake Volcano, central Japan

Ontake Volcano in central Japan was last active from ~ 100–35 Ka. The eruptions contained rhyodacite pumice and lavas in the first stage (stage O1, > 33 km³), followed by eruptions of andesite lavas and pyroclastics (stages O2 and O3, > 16 km³). Modeling of major and incompatible elements with Sr isotope ratios suggests that the primary magma was a high-alumina basalt. One andesite magma type appears to have evolved from the basalt in a closed system magma chamber, in part by fractional crystallization, and its generation included crustal assimilation. The other andesite magma type is considered to have evolved in an open system magma chamber in which repeated input of primary magma occurred together with wall-rock assimilation and fractional crystallization. The rhyodacite is inferred to have evolved in a closed system magma chamber by fractional crystallization of the second type of andesite. These genetic relationships require that the magma chamber functioned alternately as an open and a closed system. Geobarometry indicates that there may have been multiple magma chambers, located in the upper crust for the rhyodacite, near the upper–lower crust interface for the andesite and in the mid-lower crust for the basalt. These chambers were stacked to form the magma plumbing system of Ontake. Incompatible element compositions of the basalt are considered to have changed during the eruptions, suggesting that two different plumbing systems for stage O1 magma and for stages O2, O3 magmas existed during the 65 Ka of activity. Evolutionary history of the systems implies that the primary magma was introduced into the magma plumbing system each for ~ 17 500 years and that the life span of a magma plumbing system was shorter than 40 Ka.