• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.3
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• pp.159-169
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• 2007

Excessive input of organic matters from fish cage farms to the coastal waters has been considered as one of the major factors disturbing their benthic ecosystem. Sediment samples were taken from around the two fish cage zones (A and B) in Tongyeong coast in June and August 2003, to evaluate the ecological impacts of fish cage farming activity on the macrobenthic polychaete communities. Polychaete accounted for $81{\sim}87%$ of the total macrofauna individuals from each of the sampling stations. The number of species, abundance, diversity and dominant species of polychaete were rapidly changed with the distance from the fish cages. Within 10 m from the fish cages, Capitella capitata, which is a bio-indicator for the highly enriched sediments, was a dominant species and the lowest diversity was recorded. In particular, the maximum density (${\sim}18,410\;ind.m^2$) of C. capitata was found at Farm A where fish cages were more densely established within a semi-enclosed bay system. The sampling zone between 10 m and 15 m showed a rapid decrease of C. capitata with a rapid increase of the numbers of species, implying that this zone may be an ecotone point from a highly to a slightly enriched area. In the sampling zone between 15 m and 60 m, a transitional zone, which represents slightly enriched condition before normal one, was observed with additional increase and maintenance of the number of species and density of polychaete. In addition, the potential bio-indicators of organic enrichment, such as Lumbrineris longifolia and Aphelochaeta monilaris were the predominant species in the sampling zone. Multidimensional scaling (MDS) ordination plots and k-dominance curves confirmed the above results on the gradual changes in the macrobenthic polychaete communities. Our findings suggest that the magnitude of impact of fish cage farming activity on polychaete communities is probably governed by a distance from fish cage, density of fish cage and geomorphological characteristics around fish cage farm.

• The Korean Journal of Ecology
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• v.22 no.3
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• pp.169-179
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• 1999

The present study was undertaken to classify and describe the spring naturalized plant communities in old-Andong city by the methodology of the ZM school of phytosociology. As a result, the vegetation was classified into the six communities and two subcommunities: A. Bromus tectorum community A-a. Bromus japonicus subcommunity, A-b. Melica onoei subcommunity; B. Poa pratensis community; C. Rumex crispus community; D. Oenothera lamarckiana community; E. Ambrosia artemisiifolia var. eiatior community; F. Rumex conglomeratus community. The total taxa of the naturalized plant communities consisted of 31 families, 86 genera, 114 species and 13 varieties. Of which the taxa of the naturalized plant species consisted of 8 families, 21 genera, 25 species and 1 variety. The result of Bray-Curtis ordination revealed that the plots suveyed were arranged according largely to the vegetation units of' the communities. Also the interspecific affinity was examined by an analysis of interspecific association and the main component species in the communities were divided into two groups. The naturalized rate was higher in the communitise affected by strong human impacts, while was lower in the communities affected relatively less by human impacts. On the other hand the seasonal changes of the communities and the naturalized rate between the spring and the autumn were investigated. Many naturalized communities present in Spring were replaced by the other native ruderal communitues in the Autumn. The naturalized rate based on the dominance was largely decreased over from the spring to the Autumn.

• The Korean Journal of Pesticide Science
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• v.17 no.3
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• pp.200-205
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• 2013

Mating disruption experiments were evaluated and compared in several pheromone traps and sex pheromone composition ratios at commercial chestnut garden for developing alternative control method of D. punctiferalis. The highest attractive was shown in Delta traps at the effective sex pheromone ratio of 75:25 (E10-16:A1:Z10-16:A1). Comparisons of domestic and imported pheromone constituents were not significant difference in 90:10 (E10-16:A1:Z10-16:A1). But, there was significant difference in sex pheromone ratio of 75:25. D. punctiferalis was caught the highest number in Gongju area for attractive test using pheromone trap. Attractive effects with dose of pheromone were showed the highest at 2.5 mg/lure and 1 mg/lure in Gongju area and Cheongyang area respectively. However, there was no significant difference among pheromone dose in Buyeo area. These data could be useful for eco-friendly managing of D. punctiferalis in the chestnut farm.

• Journal of Preventive Medicine and Public Health
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• v.34 no.3
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• pp.284-290
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• 2001

Objectives : To evaluate the association of snoring and hyper-tension in a rural population. Methods : A population-based sample of 1,763 adults in Chonnam, Korea was investigated with questionnaires and height, weight, and blood pressure measurements. Information on the demographic characteristics, cigarette smoking, alcohol consumption, hypertension and snoring was collected through a person-to-person interview using a structured questionnaire. The level of obesity was measured by the body mass index(BMI). Hypertension was considered to be present if the average of two blood pressure measurements was greater than 140mmHg systolic or 90mmHg diastolic, or if they were currently on antihypertensive treatment. Results : The prevalence of snoring was 42.7% in men and 39.8% in women. With regard to age, snoring prevalence was 44.3% in the middle-aged group(45 to 64 years), greater than 33.9% in the younger(<45 years) group or 38.7% in the elderly($\geq65$ years) group. The snoring prevalence increased progressively with increasing BMI, but cigarette smoking and alcohol consumption was not associated with snoring. Hypertension occurred more frequently in snorers than in non-snorers (Odds ratio: 1.25, 95% confidence interval : 1.01-1.55). However after adjusting for sex, age, obesity, smoking, and alcohol use, an effect of snoring on hypertension was no longer present (Odds ratio: 1.13, 95% confidence interval = 0.90-1.41). Conclusion : These results suggest that snoring might not be associated with hypertension.

• Korean Journal of Ecology and Environment
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• v.40 no.2
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• pp.327-336
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• 2007

This study assessed ecological health using a multi-metric fish model from 15 sites in the headwater watershed of southern Han River during June${\sim}$August 1999 and then compared the health with conventional community diversity index to figure out differences between health and diversity index. For the analysis, we adopted 10 metric IBI model for regional applications. During this survey, total number of species sampled were 24 (6 families) and varied depending on magnitude of ecological disturbance and stream order. In the mountainous streams, mean proportion of sensitive and insectivore species was composed of 91% and 56%, respectively, indicating a potential healthy conditions. However, tolerant species with 66% and omnivore species with 76% were sampled from the 2nd order stream, which was shown deterioration in the physical habitat quality. In the overall watershed, mean IBI value was 38, judging as "fair" condition by the health criteria. Values of Individual IBI were closely associated with stream order and this pattern was similar to other mountainous streams showing low chemical pollutions and disturbance. Our comparison between IBI and diversity index over the stream order showed a distinct difference; Shannon-Weaver diversity index overestimated the actual community conditions and the variation range in the 2nd order stream was greater in the diversity index. Overall data suggest that the multi-metric approach may to a useful tool for stream ecosystem management and the conventional diversity index may not effective unless the stream order is considered for the stream evaluation.

• Explosives and Blasting
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• v.23 no.4
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• pp.31-44
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• 2005

In highly stressed conditions, the excavation damage zone induced by stress redistribution and disturbance must be evaluated after tunnel excavation. Therefore, the investigation of stress-induced deformation and fracture in rock is indispensable. In this study, fracture and damage mechanisms of rock induced by the accumulation of microcracks were investigated by the moving point regression technique as well as acoustic emission measured during uniaxial compression tests. Especially, the modified procedures to determine damage thresholds more systematically were newly proposed, and successfully applied to rock. From experiments, crack initiation and track damage stress levels were estimated to be $33{\~}36\%$ and $84{\~}89\%$ of uniaxial compressive strength respectively, for both of Hwangdeung granite and Yeosan marble. However, the normalized crack closure stress level for Yeosan marble was much higher than for Hwangdeung granite. In addition, the largest proportion of total axial strain in Hwangdeung granite was attributable to elastic deformation and initial microcracking. However, the greatest part of axial deformation in Yeosan marble arose from initial crack closure and unstable cracking. Finally, it was seen that unstable cracking after the crack damage stress level played a key part in the lateral deformation in rocks under uniaxial compression.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.4
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• pp.605-615
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• 2016

It is difficult to form a rational strut-tie model that represents a true load transfer mechanism of structural concrete with disturbed stressed region(s). To overcome the difficulty and handle numerous load cases with just one strut-tie model, a two-dimensional grid strut-tie model method was proposed previously. However, the validity of the method was not fully examined, although the incorporated basic concepts and new methods regarding the effective strength of concrete strut, load carrying capacity of struts and ties, and geometrical compatibility of grid strut-tie model were explained in detail. In this study, for accurate strength analysis and reliable design of reinforced concrete deep beams, the appropriateness of the two-dimensional grid strut-tie model method is verified. For this, the failure strength of 237 reinforced concrete deep beams, tested to shear failure, is predicted by the two-dimensional grid strut-tie model method, and the results are compared with those obtained by the sectional shear design methods and conventional strut-tie model methods of current design codes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.11
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• pp.1027-1033
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• 2010

A two-phase (gas-liquid) flow is a common phenomenon in fluidic systems, e.g., fluidic systems in the electro-magnetic or nuclear power generation industry and in the steel industry. The measurement of a two-phase flow is important for guaranteeing the safety of the system and for achieving the desired performance. The measurement of the void fraction, which is one of the parameters of the two-phase flow that determines the pressure drop and heat transfer coefficient, is very important. The time resolution achieved by employing the impedance method that can be used to calculate the void fraction from the impedance of the fluid is high because the electric characteristics are taken into account. Therefore, this method can be employed to accurately measure the void fraction without distortion of flow in real time by placing electrodes on the walls of the tubes. Coney analytically studied a ring-type impedance meter, which can be employed in a circular tube. The aim of this study is to experimentally verify the robustness of a three-ring impedance meter to variations in the electric conductivity of the fluid; this robustness was suggested by Coney but was not experimentally verified.

• Journal of Navigation and Port Research
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• v.36 no.10
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• pp.895-904
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• 2012

Today, the competition for hub-port is getting fierce and the shipping liners have enjoyed the increased bargaining power over the terminal operators through the mergers & acquisitions (M&A) and strategic alliances. This result leads the competition among terminal operators to attract liner companies and cargoes in their terminals. In demand side, however, there is a limited container cargo volume to handle because of a steady growth of cargo traffic. While, in supply side, continuous development of port terminals increased more competition among ports or terminals for cargoes. In particular the terminal operating market of Busan port is distorted because of the cargo competition between Busan North-port and Newport. The main purpose of this study is to suggest the stabilization measures of container terminal operating market in Busan port through analysis of the terminal operation market structures and market survey analysis method. For stabilizing the container terminal market, this study suggests the improvement of the legal and institutional system such as improvement in determining and reporting system of stevedoring tariff, establishment of fair competition rules etc., the introduction of port pooling system and adoption of volume-linked terminal lease system with cargo volume ceiling system for each terminal operator.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.93-102
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• 2003

Unconfined compression test (UC) has been widely used to determine the undrained shear strength ($c_u$) of clay, because it is convenient and economical. However, UC can not represent the behaviour of in-situ stress condition and the strength obtained by the test is generally underestimated compared to that of triaxial compression, due to no confining pressure. Therefore, a simple and practical method to correct the ($c_u$) for sample disturbance and to be used in geotechnical practice is needed. This study is aimed at proposing the method to estimate in-situ undrained shear strength from UC with suction measurement. The proposed method is based on theoretical shear strength equation of perfect sample (Noorany & Seed, 1965), and effective overburden stress and analysis results ($A_f,\phi'$) of effective stress behaviour by UC are needed for the equation. The shear resistance angle ($\phi'$) can be simply estimated through the result that $K_f$-line slope of the UC is 1.6 times higher than that of triaxial compression test. The result of this study shows that the measured strength by this method is very similar to that of the undrained shear strength by triaxial compression test (CK$_0$UC).