Ritz vectors and generation criteria for mode superposition analysis

A generation procedure of Ritz vectors to control the inclusion of static effect and the number of vectors in mode superposition dynamic analysis is presented. The original algorithm of the Ritz vectors¹⁵ is modified to improve stability in the generation procedure and to include the use of static residual. To reject unimportant Ritz vectors, cut-off criteria, which are based on the participation of mass distribution and spatial load distribution, are proposed. Numerical examples are presented to illustrate the effectiveness of the derived Ritz vectors over the eigenvectors and the performance of the cutoff criteria in the mode superposition dynamic analysis.     

Palustrine calcretes of the Cretaceous Gyeongsang Supergroup, Korea: Variation and paleoenvironmental implications

Abstract Mostly siliciclastic lacustrine deposits from five stratigraphically different formations (Jinju Formation, Jindong Formation, Geoncheonri and correlative Hwasan Formations and Dadaepo Formation, in ascending order) in the Cretaceous Gyeongsang Basin, Korea, were examined for aspects of lithofacies and pedogenesis to evaluate the relative influence of geological controls on the development of palustrine calcretes (calcretes formed from palustrine deposits). The pedogenic carbonate development of palustrine deposits in the Gyeongsang Supergroup varies from formation to formation. The highest development is in the Dadaepo Formation and the second is in the Jindong Formation. The lowest development of palustrine calcretes is in the Geoncheonri and Hwasan Formations and the Jinju Formation shows intermediate development. The more negative d¹³C values and the less negative d¹⁸O values of the Dadaepo palustrine calcretes confirm greater pedogenic development in the Dadaepo Formation. That the highest development was in the Dadaepo Formation was attributed to it having the smallest lake size, indicating that lake size is critical to palustrine calcrete development in non‐carbonate lakes under semi‐arid climate. In spite of having the largest lake size, the higher development in the Jindong Formation could have resulted from its lowest lake gradient and most arid paleoclimate. The higher development of palustrine calcretes in the Late Cretaceous deposits (Jindong Formation) than the Early Cretaceous deposits (Jinju Formation) reflect overall increase in aridity throughout the period during the deposition of the Gyeongsang Supergroup. Consequently, the diverse development of the palustrine calcretes in the Gyeongsang Supergroup indicates that the lacustrine settings varied in time and space throughout the evolution of the Cretaceous Gyeongsang Basin. Such variation in palustrine calcrete development according to the change in paleoenvironments may provide a basis to interpret the relative paleoenvironmental condition of lacustrine deposits including paleoclimate, lake size and gradient.     

Chemical and physical weathering in a hot‐arid,tectonically active alluvial system of Anza Borrego Desert,California

Investigation of chemical and physical weathering of bedrock and alluvial sediment in the Anza Borrego Desert, California, sheds light on weathering processes in hot‐arid systems and clarifies interpretations of climate from alluvial sediment. All of the alluvial sediment in the study area emanates from Cretaceous tonalite of the Peninsular Range, enabling exploration of the effects of external variables – climate, transport distance and tectonics – on the physical and chemical properties of the sediment. Chemical weathering in this area is dominated by plagioclase alteration observed in both bedrock outcrops and sediment, evinced most clearly by changes in the Eu anomaly. Biotite chemical weathering, manifested by interlayer K⁺ loss, is not evident in bedrock, but clearly observed in the sediment. Despite the weak intensity of chemical weathering (Chemical Index of Alteration = 56 to 62), fine‐grained (<63 μm) sediment displays a clear weathering trend in A–CN–K space and contains up to 25% clay minerals. Physical abrasion and grain‐size reduction in biotite during transport predominates in the sediment, whereas physical (insolation) weathering affecting bedrock is inferred from estimates of differential thermal expansion of mineral phases in response to extreme temperature changes in the study area. Chemical alteration and Brunauer–Emmett–Teller surface area both increase within the active Elsinore fault zone at the distal end of the depositional transect, reflecting tectonic‐induced fracturing and associated accelerated weathering. Extensive fracturing, together with a more humid Pleistocene climate, probably facilitated in situ bedrock weathering, preceding arid alluvial deposition in the Holocene. This study demonstrates that both climate and tectonic processes can affect chemical and physical weathering, resulting in alteration of plagioclase, leaching of K⁺ from biotite in the sediment and formation of clay minerals, even in hot, arid systems.     

Factors Affecting the Wintering Habitat of Major Fishery Resources in Southwestern Korean Waters

We investigated the temperature and salinity effects on the major fish species in the wintering grounds based on trawl surveys and oceanographic observations in the southwestern waters of Korea during March-early April in 2002-2003. The influence area of warm Kuroshio water was limited to the southwestern area of Korea in 2003 with a range of 7.7-16.3°C, 32.54-34.70 of salinity, wider than that of 2002. The number of fish species and density of major fish species in 2003 were higher than in 2002. Geographical estimation showed high proportions of species number and catches in the areas around Jeju Islands, southwestern waters and the southeastern coast of Korea. Five species; silver pomfret (Pampus echinogaster), hairtail (Trichiurus lepturus), anchovy (Engraulis japonicus), small yellow croaker (Larimichthys polyactis) and yellow goosefish (Lophius litulon) were most abundant, composing above 60% of the total catch in 2002 and 2003. More than 50% of catch in the major fish species were mostly distributed in the range of 9.5-11.0°C of temperature and 33.1-33.9 of salinity. Non-parametric estimation for the major species showed the 1st mode around 10°C and the 2nd mode at 8-9°C in 2002 and 11-14°C in 2003. A m o n g major fish species, hairtail was principally composed of juveniles, and larger individuals were caught in southeastern waters. These results are considered to be helpful for the areabased fishery management strategy for the wintering grounds of the Yellow Sea and coastal waters of Korea.     

Oxygen penetration through invertebrate burrow walls in Korean tidal flat

Macrofaunal burrows increase the surface area of the sediment-water interface, which has a great impact on the metabolism of aerobic microbes and the oscillation of reduced metabolites within the sediment. Given the importance of macrofauna in surficial sediments, the aim of this study is to examine the effects of burrow architectures on dissolved oxygen diffusion rates in comparison with unburrowed sediment, and thereby to evaluate the theoretical assumption used for modeling solute distribution in the burrow system using field samples. Employing microsensors, horizontal oxygen profiles were measured on a micrometer scale around burrows of seven invertebrates in tidal flats of the west coast of Korea. Oxygen diffusion distance through the burrow walls of seven invertebrates showed spatio-temporal variation with a range of 0.6 to 2.9 mm. Two groups of burrows were identified based on their oxygen diffusive properties relative to unburrowed sediments: 1) oxygen penetration similar to that of ambient sediments and 2) clearly enhanced oxygen penetration. Differences in the diffusive properties of the burrow wall were related to the burrow depth and diameter, existence of mucus lining on the wall, sediment grain size, and tidal phases. Also inhabitant activity was an important factor affecting oxygen penetration, which is discussed in the paper. These results further demonstrate that simplified assumptions (i.e. burrow structures are viewed as direct biogeochemical extensions of the sediment-water interface) may not be exact representation of the nature.     

Seasonal variation of freshwater budget in the Yellow and East China Seas simulated from an ocean general circulation model

This study investigates a freshwater budget in the Yellow and East China Seas (YECS) using a global f general circulation model with a regional focus on the YECS. A freshwater budget analysis finds that major freshwater contributors over the YECS change seasonally. In summer, freshwater inflow from Changjiang and positive precipitation minus evaporation (P-E) dominates freshwater outflow across the boundaries around the YECS, resulting in net freshwater gain in the YECS. In winter, evaporation, intensified by strong winds, dominates freshwater inflow from Changjiang and precipitation, while net freshwater transport across the boundaries around the YECS is negligible, causing freshwater loss in total over the YECS. Although P-E has often been assumed to be negligible by supposing that the annual mean of precipitation is nearly equal to that of evaporation, this study suggests that P-E needs to be included in the seasonal freshwater budget in the YECS.     

Comparison of Intestine Microbiota Between Wild and Farmed Korean Rockfish,Sebastes schlegelii

Ocean Science Journal - The Korean rockfish, Sebastes schlegeli, is most commonly farmed in sea cages along the coast of Korea; however, detailed information on intestinal microbiota regarding this...     

Evolution and Sedimentation Mechanisms of Estuarine Beach in the Nakdong River Estuary,Korea: Natural and Human Impact

Ocean Science Journal - Dadae Beach located in the Nakdong River estuary has been continuously evolving as the result of natural and anthropogenetic activities. Due to the geographic...     

A GIS-based logistic regression model in rock-fall susceptibility mapping along a mountainous road: Salavat Abad case study, Kurdistan, Iran

This study describes the application of logistic regression to rock-fall susceptibility mapping along 11?km of a mountainous road on the Salavat Abad saddle, in southwest Kurdistan, Iran. To determine the factors influencing rock-falls, data layers of slope degree, slope aspect, slope curvature, elevation, distance to road, distance to fault, lithology, and land use were analyzed by logistic regression analysis. The results are shown as rock-fall susceptibility maps. A spatial database, which included 68 sites (34 rock-fall point cells with value of 1 and 34 no rock-fall point cells with value of 0) was developed and analyzed using a Geographic Information System, GIS. The results are shown as four classes of rock-fall susceptibility. In this study, distance to fault, lithology, slope curvature, slope degree, and distance to road were found to be the most important factors affecting rock-fall. It was concluded that about 76?% of the study area can be classified as having moderate and high susceptibility classes. Rock-fall point cells were used to verify results of the rock-fall susceptibility map using success curve rate and the area under the curve. The verification results showed that the area under the curve for rock-fall susceptibility map is 77.57?%. The results from this study demonstrated that the use of a logistic regression model within a GIS framework is useful and suitable for rock-fall susceptibility mapping. The rock-fall susceptibility map can be used to reduce susceptibility associated with rock-fall.