• Korean Journal of Soil Science and Fertilizer
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• v.17 no.2
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• pp.90-95
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• 1984

To improve the physico-mechanical characteristics of heavy clayey paddy soils(Hwadong series) on Diluvial terrace after application of fine sand and briquette ashes, barley and rice were cultivated for 2 years. The influences of sand and briquette ashes on soil properties and on the crops were summarized as follows: 1. Application of the adding materials could not affect the yield of rice but barley yields were increased significantly about 18-19% in the plots of sand 100t/10a(clay 15% adjusted) and in the plots of briquette ashes. 2. The porosity and the content of water stable aggregates were decreased in the plots of sand and briquette ash adding. The chemical properties were slightly decreased in the plots of sands while the contents of av. $SiO_2$: and extr K were increased in the plots of briquette ashes. 3. Soil mechanical properties such as cone penetration resistance, shearing resistance and plastic index etc. were decreased while the friction resistance increased in the plots of sand and briquette ash treatments. Consequently, the adaptability to mechanization was increased. 4. The content of rice roots in subsoils (10-20cm) were increased in the plots of sand and briquette ash treatments.

• Journal of Wetlands Research
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• v.20 no.1
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• pp.72-79
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• 2018

Two planter boxes were monitored during their initial year of operation to be able to assess their stormwater runoff and pollutant reduction capabilities and investigate on the design factors affecting their performance. One of the planter boxes provided 85-100% runoff volume reduction for rainfall less than 15 mm and rainfall intensities lower than 5 mm/hr. This reduced to 50-64% during higher rainfall intensities and depths of up to 50 mm. Suspended solids, organics, nutrients, and heavy metals were satisfactorily removed at a range of 40-95%. The other planter box, however, did not produce outflow in all the events and allowed total capture of stormwater. The uncertainty regarding the fate of the runoff in that case required an investigation of the planter box's actual drainage and underground conditions which was deemed outside the scope of the study. Nonetheless, several design improvements and retrofits were suggested based on the provisions of current design guidelines to ensure that the hydraulic and water quality goals are achieved without potential damage to nearby structures. Moreover, continuous monitoring data is required to provide more accurate design evaluation and can serve as a guide in the construction of similar facilities in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.403-411
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• 2016

Recently, the number of occurrences of inundation and the severity of flood damage has increased rapidly as the frequency of localized heavy rainfall and the ratio of impervious area increased in urban areas. Most local governments focus on employing structural measures (e.g., the construction of detention reservoirs/pump stations, rehabilitation of drainage and sewer pipes) to prevent urban inundation. On the other hand, the effectiveness of implementing such structural measures is being dimished because there are already many inundation prevention facilities. The limitation of structural measures can be overcoming by employing non-structure measures, such as flood alerts and the operation of drainage facilities. This study suggests the pump operation rule (i.e., suggesting pump stop level) for a new detention reservoir operating method, which triggers the operation of a pump based on the water level at the monitoring node in urban drainage system. In the new reservoir operation, a total of 48 rainfall events are generated by the Huff distribution for determining the proper pump stop level. First, the generated rainfall events are distributed as frequencies, quartiles, and durations. The averaged system resilience value was determined to range from 1.2 m to 1.5 m is based on the rainfall-runoff simulation with rainfall generated by the Huff distribution. In this range, 1.2 m was identified considering the safety factor of 1.25 by the Standard on sewer facilities in 2011.

• Korean Journal of Construction Engineering and Management
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• v.19 no.5
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• pp.10-21
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• 2018

This study analyzes difficulties of enterprise activities in Chinese construction market by surveys on early entrants and interviews with experts. This study also suggests future strategy to enter the market by using inducement coefficient model. Korean construction companies in China are under heavy pressure to maintain requirement of licenses, despite recent deregulation. They are in dire predicament for market entry due to the Foreign Direct Investment System. It is almost impossible to participate in public projects and also it is not easy to do PPP projects. Therefore, Korean government should make more efforts to solve those issues through negotiations in FTA and GPA. For future expansion in Chinese construction market, it is highly recommended to boost cooperation models between Korea and China according to the empirical results of inducement coefficient model. Korean companies should collaborate with Chinese companies in some fields: smart city, environment and water treatment. Also, Korean government should support Korean companies by diplomatic means such as requesting for further opening of China's market. In GPA or GATS negotiation, Korean government should ask Chinese government that Korean companies can obtain order independently (without joint venture with Chinese companies) in China. Lastly, Korean construction companies should participate in construction projects ordered by international organizations such as ADB, AIIB.

• Korean Journal of Remote Sensing
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• v.12 no.2
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• pp.126-138
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• 1996

The characteristics of rapid development of the low pressure system over the East Sea from 06 to 08 Nov., 1995 has been analyzed in detail by the synoptic numerical products and satellite observations. The Low system was initially triggered the development of the baroclinic leaf cloud over the border of the northern part of Korea and China and moved eastward and then developed explosively com-ma or lambda type cloud system over the East Sea. To forecast well the general development and movement of the coastal winter cyclone over the East Sea popularly in a numerical simulation by several scientists, the large baroclinicity, continuous support of water vapor, and sequential cold outbreak over the warm sea surface have been more commonly concerned about. The cyclone which the central surface pressure was dropped 40hPa within 24 hours has often accompanied strong wind and heavy snow- or rain-fall in the winter season. In all successive observations with 12-hourly satellite imagery and analyzed meteorological variables in this period, the centers of the sea-level pressure and 500hPa geopotential height associated with this cyclone were typically illustrated by moving farther eastward using GMS combined enhanced IR images. The maxi-mum wind sustained by this system with the intensity and central pressure of tropical storm was about 60 knots with the center pressure drop of 44hPa/day similar to the North American cyclonic bomb and Atlantic storm.

• Bulletin of the Korean Chemical Society
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• v.14 no.4
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• pp.439-444
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• 1993

The aerobic oxidation of the Fe(II) complex of 1,4,8,11-tetraazacyclotetradecane, [Fe(cyclam)$(CH_3CN)_2](ClO_4)_2$, in MeCN in the presence of a few drops of $HClO_4$ leads to low spin Fe(III) species [Fe(cyclam)$(CH_3CN)_2](ClO_4)_3$. The Fe(III) cyclam complex is further oxidized in the air in the presence of a trace of water to produce the deep green binuclear bismacrocyclic Fe(II) complex $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$. The Fe(II) ions of the complex are six-coordinated and the bismacrocyclic ligand is extensively unsaturated. $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$ crystallizes in the monoclinic space group $P2_1/n$ with a= 13.099 (1) ${\AA}$, b= 10.930 (1) ${\AA}$, c= 17.859 (1) ${\AA}$, ${\beta}$= 95.315 $(7)^{\circ}$, and Z= 2. The structure was solved by heavy atom methods and refined anisotropically to R values of R= 0.0633 and $R_w$= 0.0702 for 1819 observed reflections with F > $4{\sigma}$ (F) measured with Mo K${\alpha}$ radiation on a CAD-4 diffractometer. The two macrocyclic units are coupled through the bridgehead carbons of ${\beta}$-diimitie moieties by a double bond. The double bonds in each macrocycle unit are localized. The average bond distances of $Fe(II)-N_{imine}$, $Fe(II)-N_{amine}$, and $Fe(II)-N_{MeCN}$ are 1.890 (5), 2.001 (5), and 1.925 (6) ${\AA}$, respectively. The complex is diamagnetic, containing two low spin Fe(II) ions in the molecule. The complex shows extremely intense charge transfer band in the near infrared at 868 nm with ${\varepsilon}$= 25,000 $M^{-1}cm^{-1}$. The complex shows a one-electron oxidation wave at +0.83 volts and two one-electron reduction waves at -0.43 and-0.72 volts vs. Ag/AgCl reference electrode. The complex reacts with carbon monoxide in $MeNO_2$ to form carbonyl adducts, whose $v_{CO}$ value (2010 $cm^{-1}$) indicates the ${\pi}$-accepting property of the present bismacrocyclic ligand.

• Journal of The Geomorphological Association of Korea
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• v.19 no.1
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• pp.17-27
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• 2012

Coastal dunes help stabilize the coastal landscape and protect the hinterland through dynamic interaction with sand beaches. Sometimes dune erosion occurs during the tropical cyclones, while dune recovery may naturally follow after the event. As the typhoon Kompasu passed through the Korean Peninsula early-September in 2010, it caused a rise in water in association with the storm, wave run-ups, and heavy rains in coastal areas. As the result, coastal dunes along the west coast of Korea were severely damaged during the storm. However, the degree and extent of erosion and recovery of dunes were found to be related with the condition of beach-dune systems including gradients of foreshore and front slope of the dune, sediment supply, vegetation, wind activity, and human interferences. Some dunes retreated landward more and more after the erosional event, while others recovered its original profile by aeolian transport processes mainly during the winter season. Vegetated dunes with pine trees were less recovered after the erosion than grass-covered dunes. In addition, dunes with artificial defense were more eroded and less recovered than those without hard constructions. According to the observation after the severe storm, it is likely that the sand transport process is critical to the dune recovery. Therefore, the interactions between beach and dune must be properly evaluated from a geomorphological perspective for the effective management of coastal dunes, including natural recovery after the erosion by storm events.

• Nuclear Engineering and Technology
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• v.23 no.1
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• pp.1-11
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• 1991

The objective of this study is to investigate the effect of weld line on the mechanical strengths and the process of weld line elimination in the Zircaloy-4 resistance upset welding for the fabrication of heavy water reactor fuel rods. The weld current and the amount of upset increased linearly with the main heat, in which two relations between them were derived. It was found that the threshold to obtain sound weld was 50% of main heat in terms of weld upset size, mechanical strengths and weld line elimination. The weld microstructure of resistance upset welds of Zircaloy-4 comprsied basketweave, Widmanstatten and martensite respectively by changing the main heats. Dimples on uniaxially fractured surface at weld line in the Zr-4 welds were larger and deeper compared with those on biaxially fractured surface. It was also found that the process of the weld line elimination in the resistance upset weld of Zircaloy-4 could be divided into three stages in terms of the presence of many pores, their shrinkage and elimination, and the shrinkage of the original weld interface with increasing weld currents.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.1
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• pp.64-70
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• 2007

In this experiment we transformed the Ca-bentonite into Na-bentonite with two inorganic Na-chemicals under different temperatures. These two Na-chemicals were selected among five different Na-chemicals which carries Na as cation. The swelling capacity of the Na chemical-treated bentonite was increased with increasing Na concentration, while the maximum concentration of Na solution decreased with increasing temperature. $Na_2CO_3$ was most effective in exchanging Ca ions and resulting in the highest swelling index among the Na-chemicals. The swelling index was significantly increased with increasing temperature to $100^{\circ}C$. But the equilibration time reversely affected the swelling index due to a rapid increase in evaporation of water. Within same amount of Na treatment SI slightly decreased not only with increasing contacting time but also with increasing temperature. The adsorption for the transformed Na-bentonite was increased with increasing equilibrium concentrations of Pb and Cd ions for all the activated Na-B and indigenous Ca-B and Na-B while the adsorbability of $Pb^{2+}$ onto each Na-B sample is more than that of $Cd^{2+}$. And the maximum adsorption capacity sequence of Na-B samples for Pb and Cd has been found to be 5 % $Na_2CO_3.$ - 5 % $NaHCO_3$ > 3 % $NaHCO_3$ > 3 % $Na_2CO_3$ > 1 % $NaHCO_3$ > 1 % $Na_2CO_3$ > indigenous Na-B > indigenous Ca-B, showing that there are contradictory results about the relationship of cation adsorption to CEC.

• Journal of Korean Society of Forest Science
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• v.110 no.3
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• pp.419-430
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• 2021

This study investigated spatiotemporal trends of sediment-related disasters in North Korea from 1960 to 2019 and post-disaster recovery cases based on a literature review and satellite images. Results showed that occurrence status of sediment-related disasters was initially externally reported in 1995 (during the Kim Jongil era); their main triggering factor was heavy summer rainfall. Furthermore, forest degradation rate was positively correlated with population density (R² = 0.4347, p = 0.02) and occurrence number of sediment-related disasters was relatively high on the west coast region, where both variables showed high values. This indicates that human activity was a major cause of forest degradation and thus, significantly affected sediment-related disasters in mountain regions. Finally, sediment- related disasters due to shallow landslides, debris flow, and slow-moving landslides were observed in undisturbed forest regions and human-impacted forest regions, including terraced fields, opencast mines, forest roads, and post-wildfire areas, via satellite image analysis. These disaster-hit areas remained mostly abandoned without any recovery works, whereas hillside erosion control work (e.g., treeplanting with terracing) or torrent erosion control work (e.g., check dam, debris flow guide bank) were implemented in certain areas. These findings can provide reference information to expand inter-Korean exchange and cooperation in forest rehabilitation and erosion control works of North Korea.