• Ocean Systems Engineering
• /
• v.13 no.2
• /
• pp.173-193
• /
• 2023

Reliable prediction of the motion of FOWT (floating offshore wind turbine) and associated mooring line tension is important in both design and operation/monitoring processes. In the present study, a 5MW OC4 semisubmersible wind turbine is numerically modeled, simulated, and analyzed by the open-source numerical tool, OpenFAST and in-house numerical tool, Charm3D-FAST. Another commercial-level program FASTv8-OrcaFlex is also introduced for comparison for selected cases. The three simulation programs solve the same turbine-floater-mooring coupled dynamics in time domain while there exist minor differences in the details of the program. Both the motions and mooring-line tensions are calculated and compared with the DeepCWind 1/50 scale model-testing results. The system identification between the numerical and physical models is checked through the static-offset test and free-decay test. Then the system motions and mooring tensions are systematically compared among the simulated results and measured values. Reasonably good agreements between the simulation and measurement are demonstrated for (i) white-noise random waves, (ii) typical random waves, and (iii) typical random waves with steady wind. Based on the comparison between numerical results and experimental data, the relative importance and role of the differences in the numerical methodologies of those three programs can be observed and interpreted. These comparative-study results may provide a certain confidence level and some insight of potential variability in motion and tension predictions for future FOWT designs and applications.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.11 no.4
• /
• pp.281-291
• /
• 2013

A hypothetical repository was assumed to be located at the KURT (KAERI Underground Research Tunnel) site, and the travel times of radionuclides released from three source positions were calculated. The groundwater flow around the KURT site was simulated and the groundwater pathways from the hypothetical source positions to the shallow groundwater were identified. Of the pathways, three pathways were selected because they had highly water-conductive features. The transport travel times of the radionuclides were calculated by a TDRW (Time-Domain Random Walk) method. Diffusion and sorption mechanisms in a host rock matrix as well as advection-dispersion mechanisms under the KURT field condition were considered. To reflect the radioactive decay, four decay chains with the radionuclides included in the high-level radioactive wastes were selected. From the simulation results, the half-life and distribution coefficient in the rock matrix, as well as multiple pathways, had an influence on the mass flux of the radionuclides. For enhancing the reliability of safety assessment, this reveals that identifying the history of the radionuclides contained in the high-level wastes and investigating the sorption processes between the radionuclides and the rock matrix in the field condition are preferentially necessary.

• Journal of Korean Association for Spatial Structures
• /
• v.7 no.5
• /
• pp.75-82
• /
• 2007

The present work measured and analyzed changes in the acoustics of a sound field which has a retractable ceiling. An 1/20 scale model of an openable space was built and measurement was carried out by varying the opened area of a ceiling. The most widely used room acoustic and design parameters, RT, EDT, and D50 were investigated. The results suggest that the use of RT as an acoustic design parameter may not be proper in an openable space and further it is likely to mislead the initial acoustic design of such spaces. It is mainly due to the characteristics of RT in which non-exponential decay processes are linearly fitted. Early decay times were found to be decreased in proportion to increaing the ratio of opened area. D50, an index of speech intelligibility, was effectively shows the influence of openings on the acoustics. It is also found that EDT and D50 at the seats, not directly exposed to the opened part of a ceiling, were almost linearly decreased in proportion to the ratio of opened area, while little influence was found for the opening ratio larger than 40% at the directly exposed seats to the opened part of a ceiling.

• Korean Journal of Food Science and Technology
• /
• v.31 no.6
• /
• pp.1577-1582
• /
• 1999

Carrot juice inoculated with $2\;{\times}\;10^8\;cfu/mL$ of Escherichia coli was treated with pulsed electric fields(PEF) for the purpose of a development of new cold pasteurization processes. Inactivation of E. coli in carrot juice increased with increase in intensity of the electric field strength and treatment time. The cells were suspended at concentration of ca. $2\;{\times}\;10^8$ cells per ml. A reduction of 4D was obtained at 40 kv/cm and 256 exponential decay pulses at room temperature. Critical electric field strength(Ec) and treatment time(tc) needed for inactivation of E. coli were 11.74 kV/cm and $3.6\;{\mu}s$ at room temperature, respectively. The combination of PEF and thermal treatment inactivated E. coli more effectively. The reductions of up to 5.5D were observed when the carrot juice was treated with PEF of 22.5 kV/cm and $205\;{\mu}s$ at $50^{\circ}C$. PFF treatment did not effect in color, pH, $^{\circ}Brix$, titratable acidity and ${\alpha}-,\;{\beta}-carotene$ contents of carrot juice.

• 한국해양학회지
• /
• v.28 no.3
• /
• pp.186-191
• /
• 1993

Scrippsiella trochoidea is a dinoflagellate responsible for red tide in early spring in southern coastal water. Marine bacteria appear to exert critical roles on the development and decay of phytoplankton bloom in marine ecosystem. It is likely that marine bacteria, Pseudomonas spp., share some metabolic processes with S. trochoidea. To investigate interactions between S. trochoidea and Pseudomonas spp. directly, cysts of S. trochoidea isolated from the bottom mud in Masan Bay have been germinated and cultured. From the S. trochoidea cultured medium, we have isolated Pseudomonas spp., a dominant and cultured. From the S. trochoidea cultured medium, we have isolated Pseudomonas spp., a dominant species. Both of Pseudomonas spp. and S trochoidea have been simultaneously inoculated into the sterilized sea water and cultured to examine the change of fatty acids. The major fatty acids that showed increases in composition during the dispecific culture were $C_{18:0/},{\;}C_{20:5}{\;}and{\;}C_{22:5}$ in S. trochoidea, and in Pseudomonas spp. Especially, $C_{20:5}{\;}and{\;}C_{18:0}$ were increased in S. trochoidea but decreased in Pseudomonas spp. These results strongly suggest that two species share some processes in their fatty acid metabolism.

• Nuclear Engineering and Technology
• /
• v.20 no.2
• /
• pp.120-131
• /
• 1988

A souce term model describes mathematically the source of radionuclides as they begin slow migration and decay in deep groundwater. Various source term models based on mass-transfer analysis and measurement-based source term models are reviewed. Ganerally, two processes are involved in leaching or dissolution: (1) chemical reactions and (2) mass transfer by diffusion. The chemical reaction controls the dissolution rates only during the early stage of exposure to groundwater. The exterior-field mass transfer may control the long term dissolution rates from the waste solid in a geologic repository. Mass-transfer analyses re3y on detailed and careful application of the governing equations that describe the mechanistic processes of transport of material between and within phases. If used correctly, source term models based on mass-transfer theory are valuable and necessary tools for developing reliable predictions.

• Archives of Pharmacal Research
• /
• v.25 no.2
• /
• pp.143-150
• /
• 2002

Fluorescent probes bound to DNA typically display nanosecond decay times and reveal only nanosecond motions. We extend the time range of measurable DNA dynamics using $[Ru(pby)_2(dppz)]^{2+}$ (bpy=2.2'-bipyridine, dppz=dipyrido[3,2-a2',3'-c]phenazine) (RuBD) which displays a mean lifetime near 90 ns. To test the usefulness of RuBD as a probe for diffusive processes in calf thymus DNA, we compared the efficiencies of fluorescence resonance energy transfer (FRET) using three donors which display lifetimes near 5 ns for acridine orange (AO), 22 ns for ethidum bromide (EB) and 92 ns for RuBD, with nile blue (NB) as the acceptor. The F rster distances for AO-NB, EB-NB and RuBD-NB donor-acceptor pairs were 42.3, 52.3, and $30.6{\;}{\AA}$, respectively. All three donors showed dramatic decreases in fluorescence intensities and more rapid intensity decays with increasing NB concentrations. The intensity decays of AO and EB in the presence of varying concentrations of NB were satisfactorily described by the one-dimensional FRET model without diffusion (Blumen and Manz, 1979). In the case of the long-lifetime donor RuBD, the experimental phase and modulation somewhat deviated from the recovered values computed from this model. The recovered NB concentrations and FRET efficiencies from the model were slightly larger than the expected values, however, the recovered and expected values did not show a significant difference. Thus, it is suggested that the lifetime of RuBD is too short to measure diffusive processes in calf thymus DNA.

• Journal of Photoscience
• /
• v.9 no.2
• /
• pp.55-58
• /
• 2002

The reaction center Dl protein of photosystem II is the target of photodamage by excess illumination. The Dl protein is damaged by reactive oxygen species generated by photochemical reactions and then degraded by specific proteolytic enzymes. We found that the Dl protein also cross-links with the surrounding polypeptides, such as D2 and CP43 in isolated thylakoids or photosystem II-enriched membranes from spinach under the illumination with strong visible light. The cross-linking was observed in spinach leaf discs as well when they were illuminated at higher temperature (40°C). It was also shown that the cross-linked products are digested efficiently by a protease(s) in the stroma. Thus the cross-linking/digestion processes of the Dl protein seem to comprise a new pathway in the turnover of the photodamaged Dl protein. It should be noted, however, that the cross-linked products of the Dl protein and CP43 induced by endogenous cationic radicals in the donor-side photoinhibition are resistant to proteolytic digestion. Accumulation of these cross-linked products in the thylakoids may lead to the decay of the function of chloroplasts and finally to the death of plant cells. Thus, we suggest that the quality control of photosystem II, especially removal of the cross-linked products of the Dl protein, is crucial for the survival of chloroplasts under the light stress.

• Korean Journal of Materials Research
• /
• v.13 no.3
• /
• pp.160-168
• /
• 2003

The co-firing processes for the supported type planar solid oxide fuel cell were investigated. A flat cell of $7.7${\times}$10.8\textrm{cm}^2$ was fabricated successfully by the co-firing process, in which green films were co-sintered in the forms of two layers of anode/electrolyte or of three layers of anode/electrolyte/cathode with gas distributor. A co-fired cell of two layers yielded a power of 200 ㎽/$\textrm{cm}^2$ at 608 ㎷. Its performance loss was mainly due to iR drop in the anodic gas distributor, which was attributed to poor contact between anodic gas distributor and current collector. The performance in the co-fired cell of three layers was much lower than that of two layers, which resulted from the large iR drop and activation overvoltage at the cathodic side. In the co-fired cell of two layers, the impedance analysis indicated that the performance decay during cell operation is due to both anode overvoltage and iR drop at anode side. Also the electrode reaction of the co-fired two layers' cell is considered to be controlled by activation overvoltage within the low current of 50 ㎃.

• Journal of Korean Society on Water Environment
• /
• v.20 no.2
• /
• pp.176-182
• /
• 2004

The purpose of this study was to investigate the heterogeneous catalytic ozonation of oxalic acid by manganese (Mn) doped-granular activated carbon (GAC). In order to observe the effect of the amount of Mn doped on GAC, catalysts were manufactured by varying the impregnated Mn concentration. In this paper, the following had labeled all sorts kinds of Mn-doped GAC were labeled with suitable names according to the amount (mM) of the concentration of dipping solution: They were each named as 'Mn20', 'Mn50', 'Mn100' and 'Mn200'. These experiments were performed in a batch reactor (0.5 L) and a semi-batch reactor (1 L) and Mn-free GAC was used as a blank catalyst. The ozone decay properties of each manufactured catalyst were firstly investigated to find out the reactivity between the aqueous ozone and the catalysts. Oxalic acid removal by catalytic ozonation was then performed to demonstrate the oxidative efficiencies of each catalyst.