• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2005.11a
• /
• pp.160-161
• /
• 2005

It is important to manage artificial fish reefs with installation for restoration. The instruments of survey for artificial reefs condition(location, amount etc.) is Side Scan Sonar and Multi-beam sonar. The efficient and economic survey of the artificial reefs facility is the complete survey of the SSS(Side Scan Sonar) in all area first and then the survey of the artificial reefs by MBES(Multi Beam Echo Sounder) in the finding area.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2004.05a
• /
• pp.55-60
• /
• 2004

In this study, the configuration and tension of a towing cable for side-scan sonar are predicted in an ambient flow and at an unsteady towing condition. The governing equation of three-dimensional dynamic analysis for a flexible cable is solved using a finite difference method. We successfully predict the configuration and tension of a side-scan sonar and designed the towing system. It is found in static analyses that the side-scan sonar must be towed to keep a its stable depth at a reasonable speed. The study also reveals in the transient analyses that the dominant component affecting the top tension is the tangential drag force for the larger towing speed than the critical speed, and the self weight of a towed instrument for the smaller towing speed than. It should be maneuvered for a towing vessel with good consideration for the impact effect in a cable due to tension peak when a towing speed is suddenly increase. The developed program can be applicable for three-dimensional dynamic analysis of a towing system for various marine survey instruments.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.8 no.2
• /
• pp.203-209
• /
• 2003

In this study, the configuration and tension of a towing cable for side-scan sonar are predicted in an ambient flow and at an unsteady towing condition. The governing equation of three-dimensional dynamic analysis for a flexible cable is solved using a finite difference method. We successfully predict the configuration and tension of a side-scan sonar and designed the towing system. It is found in static analyses that the side-scan sonar must be towed to keep a its stable depth at a reasonable speed. The study also reveals in the transient analyses that the dominant component affecting the top tension is the tangential drag force for the larger towing speed than the critical speed, and the soft weight of a towed instrument for the smaller towing speed than. It should be maneuvered for a towing vessel with good consideration for the impact effect in a cable due to tension peak when a towing speed is suddenly increase. The developed program can be applicable for three-dimensional dynamic analysis of a towing system for various marine survey instruments.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2001.10a
• /
• pp.26-27
• /
• 2001

Two sea survey instruments were introduced: continuous underway fish egg sampler (CUFES) and an airborne light detecting and ranging (LIDAR) for survey of epiplegic fish. We have used CUFES in ichthyoplankton surveys primarily for Pacific sardine (Sardinop sagax) eggs off California since 1996 and it is also being used in many parts of world for sardine and anchovy egg surveys. (omitted)

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.4
• /
• pp.542-548
• /
• 2022

In order to reduce marine accidents, each contracting Government needs to implement the instruments enacted and amended by the International Maritime Organization (IMO). The III Code requires each administration of the government to have a system for improvement through periodic review and evaluation and to include performance indicators in its evaluation methods. Thus, each IMO Member State needs to develop its own performance indicators. The purpose of this paper is to develop and present an evaluation model using the Balanced Scorecard (BSC) and Key Performance Indicators (KPI) in order to quantify and evaluate the level of implementation of the instruments by the administrations. From the perspective of 'III-BSC', which applies the BSC concept to the III code requirements, the Critical Success Factors (CSF) that must be secured to achieve the established vision were drawn up, and candidate KPIs for each evaluation area were developed to measure the derived key success factors and an initial study model was designed composed of four levels. The validity of the KPIs was verified and the study model was finalized using the survey design using the SMART technique. Furthermore, based on the developed study model, an evaluation model for the implementation of the BSC-based IMO instruments was developed by deriving the weights of elements for each level through AHP analysis. The developed evaluation model is expected to contribute toward improving the administrations' level of implementation of the IMO instruments as a tool for quantitatively grasping the level of performance of the implementation.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.36 no.5
• /
• pp.541-548
• /
• 2003

Species identification in hydroacoustic survey is one of the key requirements to estimate biomass of organism and to understand the structure of zooplankton community. Feasibility of species identification using two frequencies (38 and 120 kHz) was investigated on the basis of mean volume backscattering strength difference (MVBS). Virtual echogram technique was applied to two frequencies data sets that obtained from surveys in the Antarctic Ocean and Yellow Sea. Virtual echogram method using MVBS revealed the possibility of species identification, which species identification relying on visual scrutiny of single frequency acoustic data resulted in significant errors in biomass estimation. Through noise cancellation using MVBS, much of the acoustic noise caused by acoustic instruments could be removed in new virtual echogram, and the biomass estimation and data quality was improved.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.151-156
• /
• 2007

In December 2006, 2D surface streamer and Ocean Bottom Seismometer (OBS) data were acquired in the Ulleung basin in Korea where strong Bottom Simulating Reflectors (BSR) were shown as a result of 2D and 3D multichannel (MCS) reflection survey. The aim of this study is to provide another reliable source for estimating P wave velocity around BSR depth using OBS data in addition to velocity information from 2D surface seismic data. Four OBSs were deployed and four 20-km shot lines which pass two OBSs respectively were designed. To derive P wave velocity profile, interactive interval velocity analysis using ${\tau}$-p trajectory matching method (Kumar, 2005) was used for OBS data and semblance analysis was used for surface data. The seismic profiles cross the OBS instruments in two different directions yield recordings for four different azimuths. This raised the confidence for the results. All velocity profiles in the vicinity of BSR depth of four OBS sites show almost definite velocity changes which we could consider as upper BSR and free gas layer. Making comparison between velocity from OBS and that from 2D seismic semblance velocity analysis gives consistency in result.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.13 no.3
• /
• pp.295-301
• /
• 2008

Bathymetric data collected using a multi-beam echo sounder during marine scientific survey is essential for geologic and oceanographic research works. Accurate measurment of sound velocity profile(SVP) in water-column is important for bathymetric data processing. SVP can vary at different locations during the survey undertaken for wide areas. In addition, an observational error can occur when different equipments(Sound Velocity Profiler, Conductivity Temperature Depth, eXpendable BathyThermograph) are used for measuring SVP at the same water column. In this study, we used an MB-system software to show changes in bathymetry caused by variation of SVP. The analyses showed that the sound velocity(SV) changes due to the depth and thickness of thermocline had more significant effects on the resulting bathymetric data than those of surface mixed layer. The observational errors between SVP measuring instruments did not cause much differneces in the processed bathymetric data. Bathymetric survey line is better to be established to the direction that the change of temperature can be minimize to reduce the variation of SVP during the data acquisition along the survey line.

• Journal of the korean society of oceanography
• /
• v.36 no.1
• /
• pp.1-8
• /
• 2001

An in-situ four-electrode contact resistivity probe system was designed, and field-tested in submarine sediments. Seismic survey was also performed to support and compare the results of electric survey. The probe was designed to be driven to selected depths below the seafloor using a Vibracore system. The four insulated electrodes were, spaced equidistant across the wedge, were extended beyond the probe tip to minimize effects of sediment disturbance by the wedge insertion. In-situ measurements of resistivity were recorded on board by precision electronic equipment consisting of signal generators and processors, and by temperature-monitoring systems. Overall limits of Uncertainty at respective depths below the seafloor are up to ${\pm}$10 of the measured values. Best estimates of conductivity are considered to be ${\pm}$3 percent of the reported values. Resistivity measurements were made at six sites in carbonate sediments to a maximum depth of penetration of about 5 m. Average values of conductivity range between 0.88 and 1.21 mho/m. The results show the seabed is composed of alternating layers of relatively high-conductivity material (0.8 to 1.4 mho/m) in thicknesses of more or less one meter and layers about 30 cm thick having relatively low conductivities (0.4 to 0.8 mho/m).

• Geophysics and Geophysical Exploration
• /
• v.12 no.1
• /
• pp.41-48
• /
• 2009

Natural magnetic fields are attenuated by electrically conductive water. For that reason, marine magnetotelluric surveys have collected data at long periods (1000-100 000 s). The mantle structure has been the main target of seafloor magnetotelluric measurements. To ascertain crustal structure, however, electromagnetic data at shorter periods are important, e.g. in investigations of megathrust earthquake zones, or in natural resource surveys. To investigate of the former, for example, electromagnetic data for periods of less than 1000 s are necessary. Because no suitable ocean bottom electromagnetometer (OBEM) has been available, we have developed a small OBEM and ocean bottom electrometer (OBE) system with a high sample rate, which has an arm-folding mechanism to facilitate assembly and recovering operations. For magnetic observation, we used a fluxgate sensor. Field observations were undertaken to evaluate the field performance of our instruments. All instruments were recovered and their electromagnetic data were obtained. Results of the first experiment show that our system functioned well throughout operations and observations. Results of other field experiments off Tottori support the claim that the electromagnetic data obtained using the new OBEM and OBE system are of sufficient quality for the survey target. These results suggest that this device removes all instrumental obstacles to measurement of electromagnetic fields on the seafloor.