How can we observe the underwater feeding behavior of endotherms?     

Yasuhiko Naito   《Polar Science》2007,1(2-4):101-111

Marine mammals and marine birds perform diving to forage underwater. Recent technological advances have led to rapid progress in our understanding of diving behavior, but additional research is required into feeding behavior to determine the timing of prey ingestion, prey mass, and prey type. To achieve a comprehensive understanding of the foraging and diving behavior of these endotherms, it is essential to integrate information on feeding behavior with other data. The challenges involved in developing an appropriate research method have been addressed, and several methods have been tested and used in the field, including the stomach temperature method, the esophagus method for marine birds, the stomach temperature telemeter method for seals, and the beak magnet sensor method. In the present study, I review these methods, suggest the necessity of their further development in field studies, and propose a new practical method that involves the measurement of jaw movements underwater as an indicator of the feeding behavior of seals.  相似文献   

System identification of linear MDOF structures under ambient excitation     

Ser Tong Quek  Wenping Wang  Chan Ghee Koh 《地震工程与结构动力学》1999,28(1):61-77

This paper introduces the eigenspace structural identification technique for tall buildings subjected to ambient excitations that are stationary and where only the response time histories are measured. Based on the forward innovation model of the Kalman filter sequence, the actual response can be constructed as a function of the measured response time history with contamination of either displacement or velocity. The response time history is decomposed into subspace matrices using QR decomposition and Quotient Singular Value Decomposition (QSVD) techniques. These are then substituted into the least-square formulation to obtain the solution which is non-unique. Similarity transformation is applied to arrive at the desired solution employing the fact that eigenvalues of self-similar systems are identical. The advantages of this eigenspace technique are that it is non-iterative, initial estimates of the parameters to the identified are not required, well-established numerical algorithm of the decomposition techniques employed are available, and the method can handle MDOF systems efficiently. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Polyp Removal of a Bloom Forming Jellyfish, <Emphasis Type="Italic">Aurelia coerulea</Emphasis>, in Korean Waters and Its Value Evaluation     

Wonduk Yoon  Jinho Chae  Byoung-Seol Koh  Changhoon Han 《Ocean Science Journal》2018,53(3):499-507

Aurelia coerulea is a bloom forming jellyfish that first appeared before 1980 in the western and southern Korean seas and which has been blamed for huge economical losses in all fields of marine activities. As a preventive measure to reduce economical losses, polyp removal was undertaken at Lake Shihwa, Lake Saemangeum, and Masan Bay, Korea. In the course of efforts during 2 years to remove polyps, polyps were surveyed, quantified, and removed. In these areas, the initial total polyp abundance was 5.04 × 10⁹ and 46.25% of them were removed; Lake Shihwa the highest rates of removal and Lake Saemangeum the lowest. These efforts to remove polyps prevented the appearance of 1.20 × 10⁹ medusae, corresponding to 78.28 × 10⁶ kg. The cost of polyp removal was evaluated and compared with that of medusae removal. The ratio between the cost of polyp removal and that of medusae removal ranged between 0.78–3.14%, indicating large cost savings for polyp removal undertakings. However, the effect of polyp removal varied from positive to none, and we assumed that the cleared surface for polyp removal, quantity of removed polyp, and existence of polyps’ hotspots in neighboring areas were the causes of the non-effectiveness of polyp removal undertakings.  相似文献   

Particulate Flux and Cd/P Ratio of Particulate Material in the Pacific Ocean     

Shinichiro Noriki  Kazuhiro Hamahara  Koh Harada 《Journal of Oceanography》1999,55(6):693-703

Time-series Mark 7 sediment traps were deployed at three stations at 0°N, 13°N and 48°N along 175°E to investigate seasonal and spatial variations of particulate material flux. Chemical analysis of particulate material was performed for four major chemical components, viz. opal, CaCO₃, organic material and clay minerals, Cd and P in the particulate material were also determined. We discuss the characteristics of particulate material at each site and the transportation of Cd and P to deep water by the particulate material. The total mass fluxes and variation of fluxes at each site reflect oceanographic conditions, such as biological productivity and kind of major planktonic organisms. At the northern site, large mass fluxes with a spring bloom and high ratios of opal are characteristic. Relatively small mass fluxes with high ratios of CaCO₃ are distinct, and dissolution of CaCO₃ due to sinking is recognized in the middle latitude and 0°N sites. The larger flux at the lower trap than the upper trap at the equatorial site suggests influence by lateral transport in the deep water. Distinctive decreasing Cd/P ratio and CaCO₃ concentrations in the particulate material with increasing depth suggests that the change of Cd/P ratio in the intermediate and deep water occurs through the dissolution of CaCO₃. The dissolved Cd/P ratios in the deep water are proportional to the age of the deep water in the Atlantic but not in the Pacific. This is explained by the difference of kinds of particulate material transporting Cd and P in the deep water between the oceans. That is, the major planktonic organisms are planktons of CaCO₃ tests in the Atlantic Ocean and diatoms of opal tests in the North Pacific Ocean.  相似文献   

Evaluation of multiple regression models using spatial variables to predict nitrate concentrations in volcanic aquifers          下载免费PDF全文

Youn‐Young Jung  Dong‐Chan Koh  Won‐Bae Park  Kyoochul Ha 《水文研究》2016,30(5):663-675

Multiple linear regression of spatial variables including land use, soil type, and topography was applied to predict nitrate concentration and evaluate major factors affecting nitrate occurrence in springs and wells in the southern and northern areas of Jeju volcanic island, Korea. Three types of contributing area surrogates (CAS), namely circle, semicircle, and wedge, were employed to calculate the spatial variables. The regression results showed R² of 0.81–0.84 for springs and 0.74–0.77 for wells; R² values for wedge and semicircular CAS were more than 10% higher than those for circular CAS. The R² of spring models was significantly affected by both the shape and size of CAS, with optimal radii of 150–250 m and 300–400 m in the southern and northern areas, respectively, corresponding to thinner upper basaltic aquifers, and implying shorter flow paths in the southern area. The most influential variables in springs were orchards and soil types related to agriculture including silty loam and silty clay loam, indicating that nitrate levels are strongly affected by N fertilization in cultivated areas. In contrast, wells showed much less sensitivity to both shapes and sizes of CAS, with less contribution of land use and soil type to the regression, which could be attributed to a mix of multiple aquifer zones and widely different factors in the installation and operation of wells. Field parameters of electrical conductivity (EC) and pH increased the R² up to 10%, suggesting that these can be useful when regression with spatial variables yields a lower R². The optimal spatial scales for prediction of nitrate concentration and spatial variables that significantly contribute to nitrate contamination can provide relevant criteria for establishing groundwater management policies, considering the increasing anthropogenic land‐use trends on the island, where groundwater is highly sensitive to changes in spatial variables. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

A numerical study on the long term thermo-poroelastic effects of cold water injection into naturally fractured geothermal reservoirs     

Joshua Koh  Hamid RoshanSheik S. Rahman 《Computers and Geotechnics》2011

The residing fracture system and the prevailing in situ stresses have a significant impact on fluid flow and heat transfer in crystalline rocks. The long term response of fracture systems to changes in effective stresses, in particular the long term geo-mechanical effects of thermal stresses on reservoir characteristics is of particular interest to the geothermal industry.  相似文献   

Delineation of recharge patterns and contaminant transport using 3H–3He in a shallow aquifer contaminated by chlorinated solvents in South Korea     

Dugin Kaown  Dong-Chan Koh  D. Kip Solomon  Yoon-Yeol Yoon  Jaeha Yang  Kang-Kun Lee 《Hydrogeology Journal》2014,22(5):1041-1054

Stable isotopes of water and ³H–³He were used to delineate recharge patterns and contaminant transport for a granitic regolith aquifer in an industrial complex in Wonju, South Korea, that has historically been contaminated with chlorinated solvents including trichloroethene (TCE) and carbon tetrachloride (CT). Groundwater recharge mainly occurred in upgradient forested areas while little recharge occurred in the downgradient industrial areas covered with extensive sections of impermeable pavement and paddy fields. δ¹⁸O and δD data indicated that groundwater was mainly derived from summer precipitation. The apparent groundwater ages using ³H–³He ranged from 1 to 4 yrs in the upgradient area and from 9 to 10 yrs in the downgradient area. Comparison of groundwater flow velocities based on Darcy’s law and those calculated with simple mass balance models and groundwater age supported the presence of preferential pathways for TCE movement in the study area. Measureable TCE was observed in groundwater irrespective of groundwater age. Considering the 3-yr duration of the TCE spill, 14 yrs before sampling, this indicates that TCE plumes were continuously fed from sources in the unsaturated zone after the spill ended and moved downgradient without significant degradation in the aquifer.  相似文献   

Assessing sustainability of groundwater resources on Jeju Island,South Korea,under climate change,drought, and increased usage   总被引：2，自引：0，他引：2  

Aly I. El-Kadi  Suzanne Tillery  Robert B. Whittier  Benjamin Hagedorn  Alan Mair  Kyoochul Ha  Gi-Won Koh 《Hydrogeology Journal》2014,22(3):625-642

Numerical groundwater models were used to assess groundwater sustainability on Jeju Island, South Korea, for various climate and groundwater withdrawal scenarios. Sustainability criteria included groundwater-level elevation, spring flows, and salinity. The latter was studied for the eastern sector of the island where saltwater intrusion is significant. Model results suggest that there is a need to revise the current estimate of sustainable yield of 1.77?×?10⁶ m³/day. At the maximum extraction of 84  % of the sustainable yield, a 10-year drought scenario would decrease spring flows by 28 %, dry up 27 % of springs, and decrease hydraulic head by an island-wide average of 7 m. Head values are particularly sensitive to changes in recharge in the western parts of the island, due to the relatively low hydraulic conductivity of fractured volcanic aquifers and increased groundwater extraction for irrigation. Increases in salinity are highest under drought conditions around the current 2-m head contour line, with an estimated increase of up to 9 g/L under 100 % sustainable-yield use. The study lists recommendations towards improving the island’s management of potable groundwater resources. However, results should be treated with caution given the available data limitations and the simplifying assumptions of the numerical modeling approaches.  相似文献   

Application of multiple-isotope and groundwater-age data to identify factors affecting the extent of denitrification in a shallow aquifer near a river in South Korea     

Dugin Kaown  Eun-Hee Koh  Bernhard Mayer  Heejung Kim  Dong Kyu Park  Byeong-Hak Park  Kang-Kun Lee 《Hydrogeology Journal》2018,26(6):2009-2020

The extent of denitrification in a small agricultural area near a river in Yangpyeong, South Korea, was determined using multiple isotopes, groundwater age, and physicochemical data for groundwater. The shallow groundwater at one monitoring site had high concentrations of NO₃-N (74–83 mg L^?1). The δ¹⁵N-NO₃ values for groundwater in the study area ranged between +9.1 and +24.6‰ in June 2014 and +12.2 to +21.6‰ in October 2014. High δ¹⁵N-NO₃ values (+10.7 to +12.5‰) in both sampling periods indicated that the high concentrations of nitrate in the groundwater originated from application of organic fertilizers and manure. In the northern part of the study area, some groundwater samples showed elevated δ¹⁵N-NO₃ and δ¹⁸O-NO₃ values, which suggest that nitrate was removed from the groundwater via denitrification, with N isotope enrichment factors ranging between ?4.8 and ?7.9‰ and O isotope enrichment factors varying between ?3.8 and ?4.9‰. Similar δD and δ¹⁸O values of the surface water and groundwater in the south appear to indicate that groundwater in that area was affected by surface-water infiltration. The mean residence times (MRTs) of groundwater showed younger ages in the south (10–20 years) than in the north (20–30 years). Hence, it was concluded that denitrification processes under anaerobic conditions with longer groundwater MRT in the northern part of the study area removed considerable amounts of nitrate. This study demonstrates that multi-isotope data combined with physicochemical data and age-dating information can be effectively applied to characterize nitrate contaminant sources and attenuation processes.  相似文献   

Oxygen penetration through invertebrate burrow walls in Korean tidal flat     

Bon Joo Koo  Chul-Hwan Koh 《Ocean Science Journal》2013,48(4):329-338

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.  相似文献