• The Journal of Fisheries Business Administration
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• v.46 no.2
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• pp.59-74
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• 2015

This study aims to estimate optimal harvesting production, fishing efforts, and stock levels of yellow croaker caught by the offshore Stow Net and the offshore Gill Net fisheries using the current value Hamiltonian method and the surplus production model. As analyzing processes, firstly, this study uses the Gavaris general linear model to estimate standardized fishing efforts of yellow croaker caught by the above multiple fisheries. Secondly, this study applies the Clarke Yoshimoto Pooley(CY&P) model among the various exponential growth models to estimate intrinsic growth rate(r), environmental carrying capacity(K), and catchability coefficient(q) of yellow croaker which inhabits in offshore area of Korea. Thirdly, the study determines optimal harvesting production, fishing efforts, and stock levels of yellow croaker using the current value Hamiltonian method which is including average landing price of yellow croaker, average unit cost of fishing efforts, and social discount rate based on standard of the Korean Development Institute. Finally, this study tries sensitivity analysis to understand changes in optimal harvesting production, fishing efforts, and stock levels of yellow croaker caused by changes in economic and biological parameters. As results drawn by the current value Hamiltonian model, the optimal harvesting production, fishing efforts, and stock levels of yellow croaker caught by the multiple fisheries were estimated as 19,173 ton, 101,644 horse power, and 146,144 ton respectively. In addition, as results of sensitivity analysis, firstly, if the social discount rate and the average landing price of yellow croaker continuously increase, the optimal harvesting production of yellow croaker increases at decreasing rate and then finally slightly decreases due to decreases in stock levels of yellow croaker. Secondly, if the average unit cost of fishing efforts continuously increases, the optimal fishing efforts of the multiple fisheries decreases, but the optimal stock level of yellow croaker increases. The optimal harvest starts climbing and then continuously decreases due to increases in the average unit cost. Thirdly, when the intrinsic growth rate of yellow croaker increases, the optimal harvest, fishing efforts, and stock level all continuously increase. In conclusion, this study suggests that the optimal harvesting production and fishing efforts were much less than actual harvesting production(35,279 ton) and estimated standardized fishing efforts(175,512 horse power) in 2013. This result implies that yellow croaker has been overfished due to excessive fishing efforts. Efficient management and conservative policy on stock of yellow croaker need to be urgently implemented.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3B
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• pp.205-209
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• 2011

The low carrying capacity caused by the deposition in a sewer line is one of the main reason of the urban flood. Therefore, an efficient maintenance and management of the storm water drainage system is very important to prevent urban flood. In this research, the sediment transport characteristics through a pressure pipeline were examined with laboratory experiments. Bed-forms in a pipeline, sediment rates, roughness due to sediments were examined. Experimental system consists of flow circulation system with a pump and a sediment feeder at the upstream of the pipeline. Sediments were supplied into a 60 mm-diameter and 8 m-long pipe. Maximum flow rate is $30m^3/hr$, and the sediment feeding rate range is 5 g/s~19 g/s. Governing parameters and estimation equation for sediment transport rate were developed. The mean velocity (U), coefficient of viscosity (${\mu}$), unit width bed load ($q_b$), mean diameter of particle ($d_{50}$), unit weight of sediment in water (${\gamma}^{\prime}_s$) were adopted as the most influencing factors of sediment transport patterns. The prediction equation for sediment transport rate were developed with two dimensionless terms. These two dimensionless terms showed a linear relationship with high correlation coefficient.

• Weed & Turfgrass Science
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• v.7 no.2
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• pp.148-157
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• 2018

Research was initiated to evaluate four domestic and overseas organic soil amendments (SAs) on turfgrass groundcover and density and to provide basic information on practical sports turf establishment. This study was conducted in Agrostis palustris Huds. (CB) grown in sand-based root zone. A total of 20 treatments of SA+sand were prepared by mixing 10 to 50% (v/v). These amendments were SABP (Berger Peat), SAEP (Eco-Peat), SAGS (G1-Soil), and SAPP (Premier Peat). Turfgrass groundcover and density significantly varied with SAs, its mixing rate to sand and week after seeding (WAS). Cumulative turfgrass density was variable, but a great change occurred between 2 and 4 WAS. Turfgrass density at 2 WAS ranged from 36.7 (SABP 30) to 89.7% (SAGS 20), being 53.0% in differences among treatments. However, CB reached to carrying capacity around 6 WAS. Thus, most treatments were similar to 90% or so in density. At the end of study, overall groundcover ranged between 60.7 (SAEP 10) and 96.7% (SAPP 50). Proper mixing rate was variable with SAs, being 10 and 20% for SABP and SAGS, respectively. But the optimum rate was 50% for both SAEP and SAPP.

• Ocean and Polar Research
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• v.32 no.4
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• pp.449-462
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• 2010

Ongoing port baseline surveys are essential for developing ballast water management procedures in order to control unwanted or potentially risky species. Seasonal distributional patterns of marine dinoflagellate Noctiluca scintillans internationally recognized as harmful species and the related environmental factors were surveyed at Incheon, Gwangyang and Ulsan seaports in Korea from 2007 to 2009. The above three seaports were chosen because of their status as the busiest in Korea and characterized by their different bioregions. Average temperature ranged from $2.08^{\circ}C$ in winter to $26.39^{\circ}C$ in summer at Incheon, $7.22^{\circ}C$ in winter to $25.77^{\circ}C$ in summer at Gwangyang, and $11.59^{\circ}C$ in winter to $21.67^{\circ}C$ in summer at Ulsan during the study period. Average salinity varied from 26.88 in winter to 31.25 in summer at Incheon, 22.83 in winter to 33.41 in summer at Gwangyang, and 30.04 in winter to 33.90 in summer at Ulsan. Noctiluca scintillans appeared consistently at all ports during the study period, indicating its eurythermal and euryhaline nature. The highest abundances (21,813 to 41,753 $inds{\cdot}m^{-3}$) of N. scintillans were observed in May 2008 and 2009 at the outer stations of Incheon port. Abundances of between 10,000 and 30,000 $inds{\cdot}m^{-3}$ were only observed at the innermost station of Ulsan in May, while abundances of between 10,000 and 40,000 $inds{\cdot}m^{-3}$ were frequently observed throughout all stations at Gwangyang during the study period, coinciding with consistently high concentration of chlorophyll-a (hereafter chl-a) ($4.32-8.24\;{\mu}g\;l^{-1}$) compared to other ports. Spatio-temporal variation of chl-a concentration was not significantly correlated with abundances of N. scintillans (p>0.01). However, relatively high chl-a concentrations were consistently recorded along with high abundances of N. scintillans throughout all stations at Gwangyang compared to other ports. Abundances of N. scintillans observed at the three surveyed ports did not significantly (p>0.01) affect the concentration of dissolved oxygen in the surface mixed layer, indicating that the species abundances were not enough to cause reduction of dissolved oxygen during the study period. Presented results indicated that the Gwangyang seaport may provide the most suitable environment for a wide range of N. scintillans blooming compared to other ports.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.10a
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• pp.111-121
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• 1995

In Extracting the dynamic parameters for estimating the load carrying capacity and integrity of bridges, both the instrumentation and the processing the data plays important role . When the fixed point can not be secured, it is difficult and expensive to measure dynamic displacements. Even if the displacement is obtained through the integration of the acceleration data, the results can be quite different from the real behavior, because the main frequency contents can be leaked during discretized data processing. The instrumentation is used for measurements, and every measurement involves error and uncertainty, such as systematic, conformance, environmental, observational, sampling, and ranmom error. Systematic and conformance error can be remedied through the proper sellection and installation of the instruments, but sampling and random errors could not have been corrected properly and it becomes the limitation for using acceleration data. In this paper, the errors which can be occurred in numerical processing of dynamic data are referred, and the method to sellect proper sampling rate for the structural frequency range are proposed. Using the proposed method, the displacement response of the structures can be economically obtained from the measured acceleration record, and this procedure can be used properly to estimate the integrity of the bridges and infrastructures subjected to dynamic loads.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.137-144
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• 2013

The use of fiber-reinforced polymer (FRP) reinforcing bars in concrete structures has been increased as an alternative of steel reinforcement which has shown greater vulnerability to corrosion problem. However, the long-term performance of concrete members with FRP reinforcement is still questioned in comparison to the used of steel reinforcement. This study presents the results of an experimental study on the long-term behaviors of GFRP (glass fiber reinforced polymer) bar reinforced concrete beams after exposed to accelerated aging in an environmental chamber with temperature of $46^{\circ}C$ ($115^{\circ}F$) and 80% of relative humidity up to 300 days. The objectives of this research was to compare strength degradation and change of ductility between GFRP reinforced concrete beams and steel reinforcement beams after accelerated aging. Two types (wrapped and sand-coated surface) of GFRP bars and steel were reinforced. in concrete beams. Test results show that the failure modes of GFRP bar reinforced concrete beams are very similar with traditional RC beams, and the change of load-carrying capacity of steel reinforcing concrete beam is greater than that of GFRP bar reinforcing concrete beam under the accelerated aging. Test result also shows that the use of GFRP reinforcing in concrete could be introduced more brittle failure than that of steel reinforcing for practical application. The deformability factor up to compression failures indicates no significant variation before and after exposure of accelerated aging.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.417-429
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• 2008

This paper presents an experimental result to evaluate the redundancy in continuous span two plate-girder bridges which are generally classified as a non-redundant load path structure. The experiments were performed when one of the two girders is seriously cracked. To estimate the effects of bottom lateral bracing on the redundancy, the experiment variable was considered as the bottom lateral bracing, and two 1/5-scaled bridge specimens with and without lateral bracing system were fabricated. The ultimate loading tests were conducted on the damaged specimens with an induced crack at a girder in the side span. The test results showed that the load carrying capacity of damaged specimen with bracing was about 1.2 times higher than that without bracing. To evaluate the redundancy in each specimen, numerical analysis was performed to calibrate the difference of dead load between the actual bridge and the test specimens. When the dead load calibration is considered, the results showed that a continuous span two-girder bridges have a reasonable redundancy even without lateral bracing. Especially, the level of redundancy is increased by about 1.8 times when the lateral bracing is provided.

• Korean Journal of Environment and Ecology
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• v.31 no.3
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• pp.337-343
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• 2017

This study is going to contribute the activation of ecosystem services written in the 3rd National Basic Plan for Nature Conservation(2016~2025) in Korea. Meanwhile we considered the benefits that the nature has given to the humankind as free goods or services which we may consume traditionally without due payment therefore. But on account of the expansion of cities and expedition of development, as the carrying capacity of the nature has been breached, people have come to try to restore and enhance artificially such vulnerable capacity. It is necessary to compensate the opportunity cost which the land owners or occupiers have to pay for conservation and maintenance of natural capitals which yield the ecosystem services. Therefore the institutionalization of ecosystem services should be established that the consumers who enjoy such services should share the interest from enjoying services with the land owners or occupiers who produce the ecosystem services, under the legal system which will make it possible to connect the benefit sharing with the conservation of environment. However it is the first task that the present legal system could not realize the fair and equitable benefit sharing between the producers and consumers of ecosystem services. And the second task in such legal system is that the value of ecosystem services could not be fully considered in the process of development planning. According to the analysis of this study, the institutionalization of ecosystem services in the government side and the civilian side could be realized to somewhat extent, although not sufficient. Especially the transactions of ecosystem services through the private contract among stakeholder are possible in the course of development planning or without any relevancy to a development project. The final task in the institutionalization of ecosystem services is how to assess the ecosystem services and to value the economic benefits therefrom on the basis of what kinds of procedures relating to some development processes. To overcome such difficulties, it is necessary that the state, trend and change of ecosystem services confronting with a developing project should be assessed concretely at the threshold of development. It is possible to integrate the ecosystem services into the environmental impact assessment(IEA), not by way of the Act of IEA, but by way of the Decree thereof.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.119-126
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• 2011

High-speed railway raises global interests with the growing concerns on the green development and the green energy. However, since most of the infrastructure investment of Korea was focused on the highway projects for last forty years, the investment on the railway has been limited around 40~50% of that of the highway projects. In addition, due to the world economy crisis and unsatisfactory support of existing policy for the private investment project, the private investment is given a small deal of weight on the social overhead capital investment. Meanwhile, despite the world high-speed railway market is growing rapidly and the Korean contractors have won the international construction contracts over 70 billion USD, past records of railway projects are very rare. Therefore, it is required to develop strategies for encouraging private investment in the domestic market to achieve efficient high-speed railway development and for advancing into foreign high-speed railway market. This study carried out data collection and market analysis for both domestic and foreign market respectively. Through a structured questionnaire survey and expert interviews, contractors' perceptions on the high-speed railway market and needs for the government support are collected. Summary of strategies drawn from this study are as follows: 1) carrying out BTL high-speed railway projects and revising related policies; 2) upwarding incentive level for the private pre-investment projects considering the contractors' credit rating; 3) carrying out Honam-Jeju submarine railway project; 4) establishing a efficient consortium model for foreign market; 5) improving the capacity of the Korea Railway Association that support Korean contractors' foreign advancement; and 6) expand the budget for Global Infra-fund.