• Journal of the Korean earth science society
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• v.44 no.1
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• pp.13-35
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• 2023

Ocean currents play the most important role in causing and controlling global climate change. The water depth of the Yellow Sea is very shallow compared to the East Sea, and the circulation and currents of seawater are quite complicated owing to the influence of various wind fields, ocean currents, and river discharge with low-salinity seawater. The Yellow Sea Warm Current (YSWC) is one of the most representative currents of the Yellow Sea in winter and is closely related to the weather of the southwest coast of the Korean Peninsula, so it needs to be treated as important in secondary-school textbooks. Based on the 2015 revised national educational curriculum, secondary-school science and earth science textbooks were analyzed for content related to the YSWC. In addition, a questionnaire survey of secondary-school science teachers was conducted to investigate their perceptions of the temporal variability of ocean currents. Most teachers appeared to have the incorrect knowledge that the YSWC moves north all year round to the west coast of the Korean Peninsula and is strong in the summer like a general warm current. The YSWC does not have strong seasonal variability in current strength, unlike the North Korean Cold Current (NKCC), but does not exist all year round and appears only in winter. These errors in teachers' subject knowledge had a background similar to why they had a misconception that the NKCC was strong in winter. Therefore, errors in textbook contents on the YSWC were analyzed and presented. In addition, to develop students' and teachers' data literacy, class materials on the YSWC that can be used in inquiry activities were developed. A graphical user interface (GUI) program that can visualize the sea surface temperature of the Yellow Sea was introduced, and a program displaying the spatial distribution of water temperature and salinity was developed using World Ocean Atlas (WOA) 2018 oceanic in-situ measurements of water temperature and salinity data and ocean numerical model reanalysis field data. This data visualization materials using oceanic data is expected to improve teachers' misunderstandings and serve as an opportunity to cultivate both students and teachers' ocean and data literacy.

• Journal of the Korean earth science society
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• v.34 no.4
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• pp.289-302
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• 2013

In order to determine the provenance of the Huksan Mud Belt sediments in the southeastern Yellow Sea, the major and rare earth elements of the same sediments were analyzed. The surface sediments were sampled from top of piston-cores and box-cores taken at 51 sites within the Huksan Mud Belt. With the mean grain size of $5-6{\phi}$, the sediments of the study area are mud-dominated. The spatial distribution patterns show that silt content is high in the northern Mud Belt, whereas clay content increases as it moves toward the southern Mud Belt. Interestingly, the geochemical compositions both of major and rare earth elements have resulted in differences of sediment provenance. Among the major elements, plots of Fe/Al vs. Mg/Al ratios, $Al_2O_3$ vs. MgO ratios, and $Al_2O_3$ vs. $K_2O$ reveal that the Huksan Mud Belt sediments are dominated by the Korean river-derived sediments. However, the characteristics of rare earth elements infer sediments originating from the Chinese rivers. This discrepancy between the above provenances is attributed to the different contributory factors in the content of chemical elements. Considering strong correlation between major elements with grain sizes, the contents of the major elements are thought to be influenced by the grain size. However, there is a weak correlation between rare earth elements and grain sizes. The behaviour of rare earth elements may be controlled by heavy minerals, rather than grain sizes. Further study requires to solve the discrepancy arose from the difference in applied chemical tracers.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.4
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• pp.357-365
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• 2011

The variation of the dissolved inorganic nutrients were investigated four times per year in the costal area of Gunsan, Yellow Sea from 2001 to 2010. Water samples were collected at 10 stations and phsico-chemical parameters were analyzed including water temperature, salinity, suspended solids, dissolved oxygen, chemical oxygen demand, chlorophyll a and dissolved inorganic nutrients. The average of dissolved inorganic nitrogen(DIN) for ten years at Gunsan area showed similar concentration between surface and bottom. The average of DIN at surface was 0.421mg/L (0.198~0.846mg/L) and bottom was 0.344mg/L(0.148~0.717mg/L). The highest value of annual average of DIN at surface was 0.846mg/L in 2002 and the lowest value was 0.198mg/L in 2010. The percentage of ammonia, nitrite and nitrate for the average DIN of 10 years showed 27%, 3% and 70% which showed most of DIN was nitrate. Dissolved inorganic phosphate(DIP) for ten years at Gunsan area showed similar concentration between surface and bottom and DIP was decreasing from 2003 to 2010. The average of DIP of 10 years was 0.024mg/L and annual average 0.021mg/L in 2008, 0.007mg/L in 2009 and 0.008mg/L in 2010 which showed decreasing pattern from 2007 to 2010. The average of DIN/DIP ratio from 2002 to 2010 was 6.0(3.2~10.1) at surface and 4.6(2.6~7.0) at bottom. The average value of dissolved inorganic silicate from 2004 to 2010 showed 0.372mg/L at surface layer and 0.352mg/L at bottom layer and was on decreased from 2006 to 2010. The Spearman's correlation analysis was carried out to knowrelation among the salinity and dissolved inorganic nutrients at the surface and bottom layer. The correlation factor of DIN was -0.72, DIP was -0.46 and dissolved inorganic silicate was -0.63 at surface layer and DIN was -0.70, DIP was -0.44 and dissolved inorganic silicate was -0.57 at bottom layer. The dissolved inorganic nutrients at the nearshore of Gunsan was affected from the freshwater discharge of Geum river. Especially, a lot of DIN flowed into the nearshore of Gunsan from Guem river. The concentration of dissolved inorganic nutrients at Gunsan showed high at station 1, 2 and 3 and there was a little concentration differences according to the cruise time. The concentration of dissolved inorganic nutrients showed high value at the station 1, 2, 3 which exist nearshore of Gunsan city and it means these stations mainly affected by Geum river and Gunsan city. The annual average of dissolved inorganic nutrients showed gradually decreased from 2003 to 2010 and we need more research on this conditions.

• Smart Structures and Systems
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• v.10 no.1
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• pp.33-46
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• 2012

To reduce the vibration of cable-stayed bridges, conventional magnetorheological (MR) damper control system (CMRDS), with separate power supply, sensors and controllers, is widely investigated. In this paper, to improve the reliability and performance of the control system, one adaptive MR damper control system (AMRDS) consisting of MR damper and piezoelectric energy harvester (PEH) is proposed. According to piezoelectric effect, PEH can produce energy for powering MR damper. The energy is proportional to the product of the cable displacement and velocity. Due to the damping force changing with the energy, the new system can be adjustable to reduce the cable vibration. Compared with CMRDS, the new system is structurally simplified, replacing external sensor, power supply and controller with PEH. In the paper, taking the N26 cable of Shandong Binzhou Yellow River Bridge as example, the design method for the whole AMRDS is given, and simple formulas for PEH are derived. To verify the effectiveness of the proposed adaptive control system, the performance is compared with active control case and simple Bang-Bang semi-active control case. It is shown that AMRDS is better than simple Bang-Bang semi-active control case, and still needed to be improved in comparison with active control case.

• Journal of the Korea Furniture Society
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• v.21 no.5
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• pp.424-431
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• 2010

Yungneung is the royal tomb of King Jangjo (the Crown Prince Sado, 1735~1762) and his wife, Hyegyeonggung-the Lady Hong (1735~1815). King Jangjo was the second son of the 21st King Yeongjo of the Joseon Dynasty. The tomb of King Jangjo was originally established at Yangju near Seoul in 1762 and moved to Whaseong near Suwon in 1789. We examined tree-ring (dendrochronological) dates of Jeongjagak, the ceremonial hall and Bigak, the tombstone house of Yungneung. We obtained tree-ring dates of 54 wood elements. The dates of bark rings were A.D. 1785, 1786, and 1787 with completed latewoods. These tree-ring dates were well matched with the historically recorded date of two buildings, A.D. 1789 when two or three year-storage after cutting logs was considered. The results indicated that the present buildings of Yungneung was built when the royal tomb of King Jangjo was moved from Yangju to Suwon. A historical record about the construction of Yungneung, 'Hyeonyungwon-eugye' confirmed the majority of woods was moved from 'Manrichang', an official storage office in Seoul through Han river and Yellow Sea to Suwon.

• Structural Engineering and Mechanics
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• v.81 no.2
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• pp.147-161
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• 2022

The Brace-Type Shear Fuse (BSF) device is a newly proposed steel damper with excellent cumulative ductility and stable energy dissipation. In consideration of the current situation where there are not many alternatives for transversal seismic devices used in long-span three-tower self-anchored bridges (TSSBs), this paper implements improved BSFs into the world's longest TSSB, named Jinan Fenghuang Yellow River Bridge. The new details of the BSF are developed for the TSSB, and the force-displacement hysteretic curves of the BSFs are obtained using finite element (FE) simulations. A three-dimensional refined finite element model for the research TSSB was established in SAP2000, and the effects of BSFs on dynamic characteristics and seismic response of the TSSB under different site conditions were investigated by the numerical simulation method. The results show that remarkable controlling effects of BSFs on seismic response of TSSBs under different site conditions were obtained. Compared with the case without BSFs, the TSSB installed with BSFs has mitigation ratios of the tower top displacement, lateral girder displacement, tower bending moment and tower shear force exceeding 95%, 78%, 330% and 346%, respectively. Meanwhile, BSFs have a sufficient restoring force mechanism with a minor post-earthquake residual displacement. The proposed BSFs exhibit good application prospects in long-span TSSBs.

• Water for future
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• v.35 no.5
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• pp.43-50
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• 2002

The Yellow River Basin located in the Northern part of China is well-known not only as the seriously limited water sources but the greatest sediment-carrying stream in the world. The observed annual average sediment concentration in this area is $37.6kg/\textrm{mm}^3$, and 3.1% of the water volume is occupied by sediments. Due to the reason, water development has been extremely limited and it has been appeared as one of the most difficult problems in reservoir development and management. The major obstacle to surface water uses is reservoir sedimentation so that it has been strongly requested to seek the method managing sediment by optimal fashion. To solve this problem, KOWACO (Korea Water Resources Corporation) has developed various methods on the optimal reservoir management schemes including sediment management for the Upper Fenhe Basin Reservoir System at the cooperation project with Chinese. Information Variable Dynamic Programming. which is one of them, was developed for the reservoir sediment management and a set of non-dominated solutions are generated to choose the best alternative in water supply and reservoir sediment objective problem.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.445-449
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• 2005

Various methods to detect the phytoplankton/red tide blooms in the oceanic waters have been developed and tested on satellite ocean color imagery since the last two and half decades, but accurate detection of blooms with these methods remains challenging in optically complex turbid waters, mainly because of the eventual interference of absorbing and scattering properties of dissolved organic and particulate inorganic matters with these methods. The present study introduces a new method called Red tide Index (Rl), providing indices which behave as a good measure of detecting red tide algal blooms in high scattering and absorbing waters of the Korean South Sea and Yellow Sea. The effectiveness of this method in identifying and locating red tides is compared with the standard Ocean Chlorophyll 4 (OC4) bio-optical algorithm applied to SeaWiFS ocean imagery, acquired during two bloom episodes on 27 March 2002 and 28 September 2003. The result revealed that OC4 bio-optical algorithm falsely identifies red tide blooms in areas abundance in colored dissolved organic and particulate inorganic matter constituents associated with coastal areas, estuaries and river mouths, whereas red tide index provides improved capability of detecting, predicting and monitoring of these blooms in both clear and turbid waters.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.19 no.3
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• pp.43-53
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• 2011

It is well known some Foreign aircraft used to fly INCHEON FIR(Flight Information Region), especially the island of IEODO without a flight plan, even though foreign aircraft is subject to submitting a flight plan to Flight Information Center(FIC) before its flight. IEODO is a sunken rock 4.6m beneath the sea level, 149km away from Marado. Facing the Yangtze river's sea entrance horizontally and military zones of Korea and China vertically, IEODO is a very important place for national security of North East Asia because it is located at the boundary between China East Sea and Yellow Sea of South Korea. Moreover, JDZ(the 7th mine lot) is just 77NM from IEODO, which possesses natural gas eight times bigger than the gulf region and oil 4.5 times bigger than that of the U.S. In addition, INCHEON FIR, managed by MLTM(Air Traffic Control Center) and Japanese Self-Defense Force's JADIZ(Japanese Air Defense Identification Zone) are overlapping on IEODO whose air space is very complex. This paper focuses on air space, FIR, ADIZ(Air Defense Identification Zone) and related airspace system and suggests strategic implications of how to prevent foreign aircraft from invading INCHEON FIR without permission and of how to utilize the airspace efficiently.

• Advances in nano research
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• v.12 no.6
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• pp.567-581
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• 2022

The free and forced vibration in addition to electric energy harvesting of a piezoelectric disk resting on two-parameter foundation modeled by modified couple stress as well as Kirchhoff plate theory is probed. The governing equations and boundary conditions are obtained using Hamilton's principle. Then, the free and forced vibration are solved using numerical solutions, generalized differential quadrature method (GDQM) and Newmark-beta method. The forced vibration is resulted from a base excitation load. Also, the possible voltage which can be harvested from this system is obtained using generalized integral quadrature method. The validity of the formulation and solution procedure is confirmed using a compassion study. The impact of parameters such as length effect, inner to outer radius ratio, and foundations parameters on the free and forced vibration as well as energy harvesting is investigated in detail. This paper can be a basis for future studies in the area of piezoelectric harvesters in small scales.