• Journal of Korean Society of Environmental Engineers
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• v.35 no.11
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• pp.781-784
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• 2013

Ocean dumping of sewage sludge is banned. Therefore, it is needed to develop alternative treatment method. Sewage sludge and waste glass are used to prepare lightweight brick. Large amount of energy is consumed to prepare building material, because of its high preparation temperature, or above $1,200^{\circ}C$. We study to prepare lightweight brick, using sewage sludge and waste glass as raw materials in this research. Lightweight brick was made at low temperature of below $800^{\circ}C$ to reduce $CO_2$ emission by geopolymer technique. Calcination temperature, mixing ratio of sewage sludge/waste glass and water glass/water were discussed to evaluate their effect on the brick prepared. In this study, the optimal conditions for preparing bricks was $750^{\circ}C$ of firing temperature, 1.5 of mixing ratio for water glass/water and 10 : 90 wt% of sewage sludge/waste glass. At this condition, compressive strength and specific gravity of brick prepared were 5.1 MPa and 0.46, respectively. These values satisfy the criteria on a lightweight brick.

• Journal of Navigation and Port Research
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• v.28 no.10 s.96
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• pp.947-953
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• 2004

As a large scale port development in coastal waters proceeds step by step and populations in the vicinity of port are getting increased, the issue on 'how to dispose the treated municipal water and wastewater in harbor' brings peoples' concern. The submarine outfall system discharges the primary or secondary treated effluent at the coastline or in deep water, or between these two. The effluent, which has a density similar to that of fresh water, rises to the sea surface forming plume or jet, together with entraining the surrounding sea water and becomes very dilute. We intended in this paper to investigate the impact on dilution of effluent and the behavior of flume under the conditions of the seasonal and spatial temperature variations, which have not been noticeable in designing effective marine outfall system. To predict and analyze the behaviour and dilution characteristics of plume not just with the effluent temperature, but also with the seasonal variation of temperature of surround water, CORMIX( Cornell Mixing Zone Expert System)-GI have been applied. The results should be used with caution in evaluation the mixing zone characteristics of discharged water. We hope to help for the effective operation of outfall system, probable outfall design, protection of water quality, and warm water discharges from a power plant, etc.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.483-490
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• 2016

Automobile door latch is a fine design and assembly techniques are required in order to produce them in a small component assembly shape such as a spring, injection products, a small-sized motor. The door latch is fixed to not open the door of the car plays an important role it has a direct impact on the driver's safety. In this study, during trimming of the terminals of the connector main components of the car door latch, reduce rollover and conducted a research to find a suitable effective shear surface. Using the Taguchi method with orthogonal array of Finite Element Analysis and optimal Design of Experiments were set up parameters for the shear surface quality of the car door latch connector terminals. The design parameters used in the analysis is the clearance, the radius, and the blank holding force, the material of the connector terminal is a C2600. Trimming process optimum conditions suggested by the analysis has been verified by experiments, the shear surface shape and dimensions of a final product in good agreement with forming analysis results.Taguchi method from the above results in the optimization for the final rollover and effective shear surface improved for a vehicle door latch to the connector terminal can be seen that the applicable and useful for a variety of metal forming processes other than the trimming process is determined to be applicable.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.4
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• pp.374-381
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• 2020

According to international regulations, it is mandatory for navigators or engineers to acquire suitable skillsets before their designation as a duty officer on board. One of the most important elements is Maritime English (ME), wherein students are taught a required set of basic skills that enable them to process various documents related to accidents, ship conditions, and inspections. Students have to be equipped not only with the use of general English skills but also with the coherent use of technical terms and phrases. However, due to the unique circumstances that exist in the maritime domain, the methods used for imparting maritime knowledge and the manner in which it is evaluated are restricted. Hence, this study aims to utilize an online Maritime English learning and testing platform that can be accessed on smart devices to analyze its impact on the students' learning process. An experiment was conducted on two groups of cadets, one that used the platform and another group that did not. After six-week, the experiment results showed a significant difference between the ME test scores of the two groups. The test scores were further analyzed by incorporating the students' personal elements to measure the ef icacy of the ME test platform. Therefore, the learning and evaluation processes are expected to be implemented in ways that are appropriate and convenient to specific circumstances and be widely used in the field of maritime education in the future.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.4
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• pp.412-418
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• 2020

Generally, the propeller shaft that constitutes the ship shaft system has different patterns of behavior due to the ef ects of engine power, propeller load and eccentric thrust, which increases the risk of bearing failure by causing local load variations. To prevent this, different studies of the propulsion shaft system have been conducted focused the relative inclination angle and oil film retention between the shaft and the support bearing, mainly with respect to the Rules for the Classification of Steel Ships. However, in order to secure the stability of the propulsion shaft via a more detailed evaluation, it is necessary to consider dynamic conditions, including the transient state due to sudden change in the stern wakefield. In this context, a 50,000 DWT vessel was analyzed using the strain gauge method, and the effects of propeller shaft movement were analyzed on the starboard rudder turn which is a typical transient state during normal continuous rate(NCR) operation in ballast draught condition. Analysis results confirm that the changed propeller eccentric thrust acts as a force that temporarily pushes down the shaft to increase the local load of the stern tube bearing and negatively affects the stability of the shaft system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.3
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• pp.207-214
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• 2017

High voltage electric power transmitter GIS(Gas Insulated Switchgear) above 72.5kV needs to satisfy domestic Korean peninsular standard(ES-6110-0002) in KEPCO with respect to normal and special operation conditions which include internal gas pressure, dead weight, wind and seismic load. Some other requirements not described in Korean standard can be applied from other international standards such as IEC(International Electronical Committee) 62271-203 and 62271-207. The GIS is a kind of pressure vessel structure made of aluminum and filled with SF6 gas of internal pressure 0.4~0.5MPa. Finite element analysis of GIS is performed with such operational loads including seismic loading and the stability and reliability is determined according to ASME BPVC(Boiler and Pressure Vessel Code) SEC. VIII standard where the allowable stress level of the pressure vessel is suggested. The result shows that the stress of GIS is satisfied the allowable stress level and the safety factor is about 2.3 for Korean peninsular standard.

• Journal of fish pathology
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• v.24 no.2
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• pp.53-64
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• 2011

In quantitative studies of clinical signs, rock bream of adults and juveniles infected with Megalocytivirus IVS-1 isolated from rock bream (Oplegnathus fasciatus) in Korea showed average $4.49{\pm}1.13$ and $4.85{\pm}1.06$ of spleen index respectively. In challenge experiments, Megalocytivirus IVS-1 induced 100% cumulative mortality in both adult and juvenile rock bream. However we found 60% cumulative mortality in juvenile red sea bream (Pagrus major) even after 30 days of injection, which contradicted with the results of other laboratories. Interestingly, IVS-1 infected red sea bream of the same juvenile size with rock bream showed lower spleen index compared to that of rock bream. In real-time PCR, there was continuous increasing of the numbers of viral copies ($2.03{\times}10^7$ copies/mg) in the spleen of juvenile rock bream infected, which were different from those in adult rock bream showing plateau level after reaching to the peak level. Moreover, enlarged cell numbers in the infected spleen were also increased continuously in the juvenile but not in adult of rock bream, even decreased after reaching to peak level. Consequently, significant differences in clinical signs: cumulative mortality. spleen index and viral copy number were found between rock bream and red sea bream, but not between adult and juvenile rock bream. Certainly quantitative expression of clinical sign as in this study may be a way to compare the progression of megalocitiviral disease more accurately in different species or physiological conditions.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.5
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• pp.607-618
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• 2013

Marine macroalgal community structures and characteristics of ocean environmental factors were examined seasonally at four sites in Jeju Island, Korea, from March to November 2012. A total of 71 macroalgal species were identified, including 9 green, 7 brown, and 55 red algae. Peyssonnelia capensis occurred at all study sites and in all seasons. The average annual biomass of seaweed was 991.84 g wet $wt/m^2$, with seasonal variations from 543.80 g in autumn to 1,284.17 $g/m^2$ in summer. A green alga, Codium coactum, was the dominant species, occupying 21.31% (211.39 $g/m^2$) of the total algal biomass in Jeju Island. Subdominant species were Ecklonia cava and Lithophyllum okamurae, comprising 20.85% (206.75 $g/m^2$) and 19.64% (194.75 $g/m^2$), respectively, of the total algal biomass in Jeju Island. The vertical distribution of subtidal seaweeds was represented by L. okamurae at 5 m depth, C. coactum at 10 m depth, E. cava at 5-10 m depth and P. capensis at the 20 m depth level. In the present study, crustose coralline algae, which predominated on barren ground, were subdominant species at all study sites. Community indices varied between 0.51-0.63 for dominance index (DI), 5.53-8.14 for richness index (R), 0.51-0.63 for evenness index (J'), and 2.04-2.32 for diversity index (H'). On the basis of seaweed biomass and community indices, Sinchang was the best preserved coastal area, showing maximal values in biomass, and evenness- and diversity-indices, and minimal value in the dominance index, representing stable environmental conditions. In contrast, the Onpyung and Topyeong sites, located near tourist venues such as Udo and Seogwipo were relatively poor habitats based on community indices and biomass. The present results could imply that climate changes alter seaweed community structure, and long-term monitoring of the study sites is required.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.2
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• pp.15-22
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• 2012

The variation in the wind speed with height above ground is called the wind shear profile. In the field of wind resource assessment, analysts typically use one of two mathematical relations to characterize the measured wind shear profile: the logarithmic profile (log law) and the power law profile (power law). The logarithmic law uses the surface roughness as a parameter, and the power law uses the power law exponent as a parameter. The shape of the wind shear profile typically depends on several factors, most notably the roughness of the surrounding terrain and the stability of the atmosphere. Since the atmospheric stability changes with season, time of day, and meteorological conditions, the surface roughness and the power law exponent also tends to change in time. For this study, Using the observed data from Met-mast, located in Pyeongdae, Handong in Jeju. we used the matlab and windograper to calculate roughness length and the law exponents. These calculations are similar to reference the data, but they have different ranges. In the ocean case, each reference data and calculated data was the same, but the crop area is higher than the earlier studies. In addition, the agricultural village is lower than the earlier studies.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.42-51
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• 2016

We investigated the distribution of dissolved nutrients, phytoplankton community structure and utilization of nitrogen compounds by dominant species in the southwestern part of East Sea in September, 2014. Dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) were lower in the surface layer, and concentrations were increased with depth. Dissolved organic nitrogen (DON) and dissolved organic phosphorus were the opposite of dissolved inorganic nutrients. Although DIN DIP ratio in all of the water masses was higher than Redfield ratio (16), DIN : DIP ratio in mixed layer was about 2, indicating that inorganic nitrogen is the limiting factor for the growth of phytoplankton. In particular, DON proportion in dissolved total nitrogen was about 88 % in the mixed layer where inorganic nitrogen is limiting factor. The dominant species Chaeotceros debilis and Prorocentrum minimum were able to grow using DIN as well as DON such as urea and amino acids. Therefore, DON utilization of phytoplankton may play a role as a survival strategy in the DIN-limited conditions of East Sea.