Nonlinear time–domain analysis of motion-restrained pneumatic floating breakwater

A pneumatic-type floating breakwater is simulated in the time–domain to evaluate wave blocking and wave energy absorption. For accurate nonlinear time–domain simulation, a fully nonlinear numerical wave tank (NWT) technique has been used. In the present study, the NWT for the pneumatic breakwater is extended to the case of restrained body motion using the mode-decomposition method in the acceleration potential field. In particular, the effect of individual body motion coupled with pneumatic damping in the chamber is investigated for the case in which the breakwater is only allowed to move one degree-of-freedom: for instance, using a heave-only allowable body. The present results are compared with various motion cases as well as a box-shaped breakwater.     

Hydrologic modelling of the effect of snowmelt and temperature on a mountainous watershed

Snowmelt-runoff modelling in a mountainous basin is perceived as difficult due to the complexity of simulation. Theoretically, the snowmelt process should be influenced by temperature changes. It is still controversial as how to incorporate the temperature changes into the snowmelt-runoff model in a mountainous basin. This paper presents the results of a study in the North Fork American River basin where the snowmelt-runoff mechanism is modelled by relating the temperature changes to the elevation band in the basin. In this study, a distributed hydrologic model is used to explore the orographic effects on the snowmelt-runoff using the snowfall-snowmelt routine in Soil and Water Assessment Tool (SWAT). Three parameters, namely maximum snowmelt factor, minimum snowmelt factor, and snowpack temperature lag were analysed during the simulation. The model was validated using streamflow data from October 1, 1991 to September 30, 1994 with and without considering the elevation band. The result of this study suggests that the snowmelt-runoff model associated with the elevation band better represents the snowmelt-runoff mechanism in terms of Nash–Sutcliffe coefficient (E _NS ), R ², and Root Mean Square Error (RMSE).     

Geochemical survey of rare earth elements (REEs) in the concealed ore body of Hongcheon,Korea

Because of the risk of diminishing supplies of rare earth elements (REEs) worldwide due to China’s dominance over REE supply, the necessity of developing domestic resources of REE has been realized in other countries. To explore new ore bodies, a geochemical survey was conducted at one existing carbonatite REE deposit in the Hongcheon area of Korea. Proper sampling strategies and baseline data for the interpretation of the results were determined through a pilot study conducted in the area. Enrichment in the concentration of light REE (LREE) over that of heavy REE, which is typical in carbonatite-type deposits, was observed in stream sediments and heavy mineral samples collected during the geochemical survey. Maximum concentrations of LREE were 2,299 and 27,798 mg/kg for stream sediments and heavy minerals, respectively. Among LREEs, La and Ce are the dominant components of all REEs, comprising approximately 68 % of mean concentrations. Considering the distribution pattern of La + Ce contents and the associations with the existing outcropping ore bodies, the zone of prospective REE mineralization was determined to be in the south-western part of the area. A detailed follow-up soil survey of the zone found even higher concentrations of La and Ce (2,450 and 3,100 mg/kg, respectively), and suggested the possible extension of the existing ore bodies. Likewise, a systematic geochemical survey for REE is feasible for locating concealed ore bodies in the area, where the mineralization is mostly covered with soil, and rock outcrops are scarce.     

Reduction of future disaster damages by learning from disaster experiences

This paper examines the effect of a country’s own past disaster experiences and nearby countries’ past experiences on subsequent disaster damage. We use global disaster data from 1990 to 2010, which include disaster-related death tolls for both natural and technological disasters that are further divided into sub-categories. Overall, we find evidence of a reduction effect of past disaster damage on future disaster damage. More detailed analyses show that an adaptation effect seems to be present for certain combinations of disaster types and levels of economic development. The results show that a country’s own experiences reduce future damage for natural disasters but that the marginal effect is larger for lower-income countries. On the other hand, for technological disasters, a robust impact of experiences was found only in higher-income countries. In terms of the disaster experiences of nearby countries, the adaptation effect was found only for natural disasters, and the marginal impact was relatively higher for higher-income countries.     

Assessing drought conditions through temporal pattern,spatial characteristic and operational accuracy indicated by SPI and SPEI: case analysis for Peninsular Malaysia

Natural Hazards - A strong understanding of severe drought conditions is important for its mitigation and damage alleviation. Given the Peninsular Malaysia’s drought vulnerability and its...     

Effects of biochar, cow bone, and eggshell on Pb availability to maize in contaminated soil irrigated with saline water

Toxicity of heavy metals adversely affects environment and human health. Organic materials derived from natural matters or wastes have been applied to soils to reduce the mobility of contaminants such as heavy metals. However, the application of cow bone powder (CB), biochar (BC), and eggshell powder (ES) is rarely investigated for the reduction of Pb bioavailability in soils irrigated with saline water. The objective of this study was to assess the effectiveness of CB, BC, and ES additions as immobilizing substances on Pb bioavailability in shooting range soil irrigated with deionized and saline water. Each additive of CB, BC, and ES at 5 % (w/w) was mixed with soils and then the deionized and saline water were irrigated for 21 days. With deionized water irrigation, the soils treated with CB, BC, and ES exhibited higher pH when compared with saline water irrigation. With saline water irrigation, the electrical conductivity, water-soluble anions, and cations were significantly increased in soils treated with CB, BC, and ES. The water-soluble Pb in soils treated with CB, BC, and ES was significantly decreased with saline water irrigation. On the other hand, the water-soluble Pb in soil treated with CB was increased with deionized water irrigation. Only BC with saline water irrigation decreased the Pb concentration in maize shoots.     

A linear projection for the timing of unprecedented climate in Korea

Recently we have had abnormal weather events worldwide that are attributed by climate scientists to the global warming induced by human activities. If the global warming continues in the future and such events occur more frequently and someday become normal, we will have an unprecedented climate. This study intends to answer when we will have an unprecedented warm climate, focusing more on the regional characteristics of the timing of unprecedented climate. Using an in-situ observational data from weather stations of annual-mean surface air temperature in Korea from 1973 to 2015, we estimate a timing of unprecedented climate with a linear regression method. Based on the in-situ data with statistically significant warming trends at 95% confidence level, an unprecedented climate in Korea is projected to occur first in Cheongju by 2043 and last in Haenam by 2168. This 125-year gap in the timing indicates that a regional difference in timing of unprecedented climate is considerably large in Korea. Despite the high sensitivity of linear estimation to the data period and resolution, our findings on the large regional difference in timing of unprecedented climate can give an insight into making policies for climate change mitigation and adaptation, not only for the central government but for provincial governments.     

格列菲列岛的地质地球物理研究

本文是中、韩国际合作项目“黄海地质地球物理场特征研究”的一部分 .具体研究了格列菲列岛的基础地质问题及地球物理场特征 .格列菲列岛是由三个小岛组成的位于黄海中部的一组群岛 ,位于朝鲜半岛布格重力异常正值区 ,莫霍面埋深在 2 9km左右 .三个岛屿主要由安山集块岩构成 .安山集块岩是由大小不同的火成岩碎块和熔岩混合而成 .火成岩的碎块成分主要为石英岩、片岩、片麻岩、玄武岩、安山岩和流纹岩 .主要节理方向为NE10°～NE2 0°,倾角近乎垂直 ;另一组节理为NW70°～NW80° ,倾角也近垂直 .本研究为我们了解这个地区的基础地质情况 ,岩石物性和随后进行的黄海海域典型剖面的地球物理物性反演工作以及地质模型的建立 ,打下重要基础 .     

Radiolarians from the Pohang Basin,Southeast Korea and Paleoceanographic Implications

We identified a total of 101 species and two subspecies of radiolarians belonging to 56 genera from 95 samples collected from the Hagjeon and Duho Formations in the Pohang Basin of the southeastern Korean Peninsula. On the basis of the biostratigraphic range of Cyrtocapsella cornuta and Theocorys redondoensis, the depositional period of the upper Hagjeon and lowest Duho Formations was determined to be early to late Middle Miocene. The occurrence of deep-dwelling radiolarians indicates that the paleobathymetry seems to become gradually progressing toward an upper bathyal environment in the middle part of the Hagjeon Formation. However, we prefer to accept another interpretation for the occurrence of deep-sea indicators in the Hagjeon and the lowest part of the Duho Formations, and consider the presence of a region of upwelling cold water that might have simulated a deep-water environment in relatively shallow water. This interpretation is based on the present upwelling of a cold-water mass off the southeast coast of Korea, the occurrence of upwelling microfossils from the Pohang Basin, and the effect of the closing of the Korea Strait approximately 15 Ma. We also considered that the uppermost part of the studied section represents a shallow-water environment.     

Dinosaur tracks from the Cretaceous of South Korea: Distribution, occurrences and paleobiological significance

Abstract   Abundant dinosaur fossils including dinosaur footprints, eggs and nests, teeth and bones have been found from the Cretaceous non-marine deposits of Korea. Among them, dinosaur tracks are the most distinctive, and some track sites are among the most famous in the world. Until now, 27 dinosaur track localities have been discovered from the Cretaceous strata in the Gyeongsang Basin and several small basins. Ornithopod tracks are most abundant at most Korean track sites, and most of them are identified as Caririchnium ; that is, large ornithopod footprints with wide hoof impressions. Most theropod tracks are found in Neungju Basin and they consist of various types of small or medium-sized bird-like footprints, and other large footprints. Sauropod tracks are also abundant in the Gyeongsang Basin. The sauropod tracks vary in size, shape, and pattern of trackway, and suggest that diverse sauropods existed in this area. These diverse tracks in South Korea suggest that various dinosaurs flourished at the margins of lakes distributed in the southern part of the Korean Peninsula during the Cretaceous.