• Coupled systems mechanics
• /
• v.11 no.3
• /
• pp.267-284
• /
• 2022

Due to the high usage of ABS in industries, such as aerospace, auto, recreational devices, boat, submarines, etc., the purpose of this project was to find a way to weld this material, which gives advantages, such as affordable, high speed, and good connection quality. In this experimental project, the friction welding method was applied with parameters such as numerical control (NC) machine with two different speeds and three cross-sections, including a flat surface, cone, and step. After the end of the welding process, samples were then applied for both tensile and bending tests of materials, and the results showed that, with increasing the machining velocity Considering of samples, the friction of the surface increased and then caused to increase in the surface temperature. Considering mentioned contents, the melting temperature of composite materials increased. This can give a chance to have a better combination of Nanomaterial to base melted materials. Thus, the result showed that, with increasing the weight percentage (wt %) of Nanomaterials contents, and machining velocity, the mechanical behavior of welded area for all three types of samples were just increased. This enhancement is due to the better melting process on the welded area of different Nano contents; also, the results showed that the shape of the welding area could play a significant role, and by changing the shape, the results also changed drastically.A better shape for the welding process was dedicated to the step surface.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.13 no.3
• /
• pp.53-63
• /
• 2010

The global sea level rise has an effect on eco-environmental change by the inundation and erosion in the coastal area. Forecasting model on the change of morpho-ecological environments by the sea level change will give us information for coastal area management by predicting environmental changes of the up-coming future. This research aimed to foresee eco-environmental changes by the sea level rise in coastal area. Prediction model used SLAMM model developed to forecast coastal changes by IPCC scenario. The model predicted centennial environmental changes in the mouth of Han river and Nakdong river, Suncheon and Hampyeung bay as case areas. To sum up the research findings, in the estuary of the Han river, tidal flat was gradually disappeared from the year 2075, scrubmarsh and saltmarsh belts were developed. In the Nakdong River estuary, scrubmarsh was decreased from the year 2025, tidal flat was deposited from the year 2050, and also, the Gimhae plain was partially inundated, and wetlands were formed. In the Hampyeung bay, saltmarsh was deposited in the year 2025, tidal flat expanded until 2050 was partially submerged after that time. Tidal flat of Suncheon bay was disappeared by the inundation after 2025, and saltmarsh was developed in the embayment.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.13 no.3
• /
• pp.198-205
• /
• 2010

The purpose of this study is to investigate the characteristics of the grain size distribution and organic matters to understand the current status of the tidal flat sediment for efficient management of Suncheon Bay. We investigated the characteristics of the surface sediments in the mouth area of the Suncheon Bay at fifteen stations in April and July, 2009. Specific conclusions were as follows. The sediments in the most part of tidal flat was shown as muddy facies(clay and silt contents was more than 90%), whereas in the tidal river affected by water flow from the Dongstream was shown as sandy facies. The analyzed values of the tidal flat sediment were in the range of $1.9{\sim}3.8{\phi}$(mean $2.5{\phi}$) for sorting, and -1.5~3.2(mean -0.3) for skewness, and 1.5~14.1(mean 3.9) for kurtosis. So we knew that the tidal flat sediments in the Suncheon Bay was mainly composed by fine-grained sediment. Erosion was happened in the tidal river, whereas sedimentation was occurred in the tidal flat. The most of organic matters was derived from the Dongstream. Total organic matters shown as ignition loss was 5.75%, COD and $H_2S$ values were lower than the eutrophication level(COD; 20.0 mg/g dry, $H_2S$; 0.2 mg S/g dry). From our research the tidal flat of the Suncheon Bay is relatively fine, but a part of the flat was exceed the environmental standard. So we have to establish effective countermeasures to reduce the organic matters and nutrients derived from stream for environmental preservation of the Suncheon bay and conduct scientifically sustainable monitering for streams flowing into Suncheon Bay and tidal flat.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.6
• /
• pp.687-697
• /
• 2019

By monitoring sediment grain size and level variation of tidal flat surface for 6 years (2005-2011), and also by mooring TISDOS (tidal-flat sediment dynamics observation system) on the low intertidal flat in 2008, we investigated the sedimentary environment of tidal flat in the dammed Yeongsan River Estuary. The tidal flat of the Yeongsan River Estuary lost 82 % of its area because of coastal development projects, and a narrow tidal flat below mean sea level now remains. Most of the tidal flat sediments are composed of silt up to 70-94 %, and show the characteristics of clay deficiency and silt dominance. This is closely related with the coastal development, which led to the destruction of high tidal flats where most mud settled, and the modification of tidal current patterns. Moreover, the estuarine tidal-flat sediments reveal seasonal variation. They are coarse with abundant silt during windy autumn to spring, fine with abundant clay during the less-windy and high-discharge summer. This phenomenon indicates that the behavior of sediment particles on the low intertidal flats of the Yeongsan River Estuary is influenced by wind waves for silt and fresh water discharge and the tidal process for clay. Monitoring results of the altitude of tidal flat surface showed that the study area had eroded at an average rate of -2.6 cm/y during the period of 2005-2011, and also that an unusual deposition with a rate of 4 cm/y occurred in 2010. The erosion can be explained by an increased tidal amplitude and a strengthened ebb-dominant tidal asymmetry after the construction of an estuary dike and the Yeongam Kumho Seawall. The deposition in 2010 seems to have been closely related to the mass production of suspended materials from dredging of the estuary.

• The Korean Journal of Malacology
• /
• v.29 no.1
• /
• pp.51-63
• /
• 2013

To assess the effect of environmental factors on the sustainability of cultured production shellfish, we investigated the habitat characteristics of tidal flat (Namhae-po in Taean). We measured the physiochemical parameters (temperature, salanity, pH, dissolved oxygen and nutrients) and the geochemical characteristics (chemical oxygen demand, ignition loss, C/N ratio and C/S ratio). Surface sediments were collected from several site of tidal flat to examine the geochemical characteristics of both the benthic environment and heavy metal pollution. The grain size for research area of tidal flat were similar at the ratio of silt and clay in comparison with the other site of it. The C/N ratio was more than 5.0, reflecting the range arising from the mix of marine organism and organic matter. The C/S ratio (about 2.8) showed that survey area had anoxic or sub-anoxic bottom conditions. The enrichment factor (Ef) and index of accumulation rate (Igeo) of the metals showed that those research areas can be classified as heavily polluted, heavily to moderately polluted, or more or less unpolluted, respectively. Adult surf clam (Mactra veneriformis) density was highest at St. 2 (middle part of the Namhae-po), on the other hand, surf clam spat density was highest at St. 3 (lower part of the Namhae-po). Heavy rain, terrigenous suspended clay with fresh water from neighboring agricultural land, and severe high air temperature during summer could be thought as detrimental causes of spat and adult mortality in Namhae-po tidal flat. We suggested that the growth of shellfish in the tidal flat was effected by the various environmental conditions, so an improvement in the cultured method was needed.

• Geophysics and Geophysical Exploration
• /
• v.11 no.3
• /
• pp.197-203
• /
• 2008

A shallow high-resolution seismic reflection survey was carried out at the Mineopo tidal flat on the western coast of Korea. The purpose of the survey was to investigate shallow sedimentary structure of the tidal flat associated with the recent sea level change. A total of 795 shots were generated at 1 m interval from a 5-kg hammer source and recorded on 48 channels of 100 Hz geophones along two mutually perpendicular profiles. The water-saturated ground condition resulted in suppressed ground rolls by significantly decreasing rigidity. In addition, seismic velocities over 1500 m/s provided easy segregation of reflected arrivals from lower velocity noise. As a consequence, seismic sections from the study area show significantly higher resolution and signal to noise ratio than conventional land seismic sections. The tidal flat consists of 5 sedimentary sequences above acoustic basement. The seismic sections reveal the continuous structure of the tidal flat formed in association with sea level rise during the Holocene.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.38 no.4
• /
• pp.345-352
• /
• 2020

To preserve and restore tidal flats and prevent safety accidents, it is necessary to construct tidal flat topographic information including the exact location and shape of tidal creeks. In the tidal flats where the field surveying is difficult to apply, airborne LiDAR surveying can provide accurate terrain data for a wide area. On the other hand, we can economically obtain relatively high-resolution data from UAV (Unmanned Aerial Vehicle) surveying. In this study, we proposed the methodology to generate high-resolution topographic information of tidal flats effectively by integrating airborne LiDAR and UAV point clouds. For the purpose, automatic ICP (Iterative Closest Points) registration between two different datasets was conducted and tidal creeks were extracted by applying CSF (Cloth Simulation Filtering) algorithm. Then, we integrated high-density UAV data for tidal creeks and airborne LiDAR data for flat grounds. DEM (Digital Elevation Model) and tidal flat area and depth were generated from the integrated data to construct high-resolution topographic information for large-scale tidal flat map creation. As a result, UAV data was registered without GCP (Ground Control Point), and integrated data including detailed topographic information of tidal creeks with a relatively small data size was generated.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.37 no.4
• /
• pp.219-231
• /
• 2019

The specifications of signboards are set for each type of signboards, but the shape and size of the signboard actually installed are not uniform. In addition, because the colors of the signboard are not defined, so various colors are applied to the signboard. Methods for recognizing signboards can be thought of as similar methods of recognizing road signs and license plates, but due to the nature of the signboards, there are limitations in that the signboards can not be recognized in a way similar to road signs and license plates. In this study, we proposed a methodology for recognizing plate-type signboards, which are the main targets of illegal and old signboards, and automatically extracting areas of signboards, using the deep learning-based Faster R-CNN algorithm. The process of recognizing flat type signboards through signboard images captured by using smartphone cameras is divided into two sequences. First, the type of signboard was recognized using deep learning to recognize flat type signboards in various types of signboard images, and the result showed an accuracy of about 71%. Next, when the boundary recognition algorithm for the signboards was applied to recognize the boundary area of the flat type signboard, the boundary of flat type signboard was recognized with an accuracy of 85%.

• The Korean Journal of Ecology
• /
• v.24 no.3
• /
• pp.181-189
• /
• 2001

This study was conducted to clarify the characteristics, and proper way of protection and management of bird community in Geum river estuary from Nov. 1997 to Oct. 1998. Water was the most dominant factor of habitats. And there were cultivated area, forest, constructed area, reed bed and tidal fiat in study area. Total 104 bird species were recorded in Geum river estuary. Maximum 46 species in Apr. and 51,002 individuals in Feb. were observed. Dabbling ducks used islands and shallow area of river, and tidal flat. Gulls and waders were distributed in estuary and geese were in islands of the upstream and cultivated area of Sipjadeul. For the maintenance, protection and management of bird community in Geum river estuary, diversity of natural habitats, such as, tidal flat, cultivated area, islands and reed bed, should be maintained.

• Korean Journal of Remote Sensing
• /
• v.39 no.4
• /
• pp.409-423
• /
• 2023

North Korea is carrying out reclamation activities in tidal flat areas distributed throughout the west coast. Previousremote sensing research on North Korean tidal flats either failsto reflect recent trends or focuses on identifying and analyzing tidal flats. Thisstudy aimsto quantify the impact of recent reclamation activitiesin North Korea's coastal areas and contribute knowledge useful for determining the best remote sensing methods for coastal areas with limited accessibility, such as those in North Korea. Using Landsat-8 OLI images from 2014-2022, we analyzed land cover changesin an area on the west coast of Pyeonganbuk-do where reclamation activities are underway. Unsupervised classification using the normalized difference water index and the random forest classification technique were each used to divide the study area into classification groups, and changes in their areas over time were analyzed. The resultsshow a clear decrease in the water area and a tendency to increase cultivated area,supporting the evidence that North Korea'sreclamation isfor agricultural land expansion.Along coasts behind seawalls, the water area decreased by nearly half, and the cultivated area increased by over 2,300%, indicating significant changes and highlighting the anthropogenic nature of the cover changes due to reclamation. Both methods demonstrated high accuracy, making them suitable for detecting cover changes caused by reclamation. It is expected that further quality research will be conducted through the use of high-resolution satellite images and by combining data from multiple satellites in the future.