• Geomechanics and Engineering
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• v.37 no.3
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• pp.293-306
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• 2024

Influenced by the alternating effects of dynamic and static pressure during the mining process of close range coal seams, the surrounding rock support of cross mining roadway is difficult and the deformation mechanism is complex, which has become an important problem affecting the safe and efficient production of coal mines. The paper takes the inclined longwall mining of the 10304 working face of Zhongheng coal mine as the engineering background, analyzes the key strata fracture mechanism of the large inclined right-angle trapezoidal mining field, explores the stress distribution characteristics and transmission law of the surrounding rock of the roadway affected by the mining of the inclined coal seam, and proposes a segmented and hierarchical support method for the cross mining roadway affected by the mining of the close range coal seam group. The research results indicate that based on the derived expressions for shear and tensile fracture of key strata, the ultimate pushing distance and ultimate suspended area of a right angle trapezoidal mining area can be calculated and obtained. Within the cross mining section, along the horizontal direction of the coal wall of the working face, the peak shear stress is located near the middle of the boundary. The cracks on the floor of the cross mining roadway gradually develop in an elliptical funnel shape from the shallow to the deep. The dual coupling support system composed of active anchor rod support and passive U-shaped steel shed support proposed in this article achieves effective control of the stability of cross mining roadways, which achieves effective control of floor by coupling active support and preventive passive support to improve the strength of the surrounding rock itself. The research results are of great significance for guiding the layout, support control, and safe mining of cross mining roadways, and to some extent, can further enrich and improve the relevant theories of roof movement and control.

• Advances in nano research
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• v.16 no.2
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• pp.111-125
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• 2024

Recently, a lot of research has been done on the analysis of axial vibrations of homogeneous and FG nanotubes (nanorods) with various aspects of vibrations that have been fully mentioned in history. However, there is a lack of investigation of the dynamic internal resonances of FG nanotubes (nanorods) between them. This is one of the essential or substantial characteristics of nonlinear vibration systems that have many applications in various fields of engineering (making actuators, sensors, etc.) and medicine (improving the course of diseases such as cancers, etc.). For this reason, in this study, for the first time, the dynamic internal resonances of FG nanorods in the simultaneous presence of large-amplitude size dependent behaviour, inertial and shear effects are investigated for general state in detail. Such theoretical patterns permit as to carry out various numerical experiments, which is the key point in the expansion of advanced nano-devices in different sciences. This research presents an AFG novel nano resonator model based on the axial vibration of the elastic nanorod system in terms of derivation from large-amplitude size dependent internal modals interactions. The Hamilton's Principle is applied to achieve the basic equations in movement and boundary conditions, and a harmonic deferential quadrature method, and a multiple scale solution technique are employed to determine a semi-analytical solution. The interest of the current solution is seen in its specific procedure that useful for deriving general relationships of internal resonances of FG nanorods. The numerical results predicted by the presented formulation are compared with results already published in the literature to indicate the precision and efficiency of the used theory and method. The influences of gradient index, aspect ratio of FG nanorod, mode number, nonlinear effects, and nonlocal effects variations on the mechanical behavior of FG nanorods are examined and discussed in detail. Also, the inertial and shear traces on the formations of internal resonances of FG nanorods are studied, simultaneously. The obtained valid results of this research can be useful and practical as input data of experimental works and construction of devices related to axial vibrations of FG nanorods.

• Advances in concrete construction
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• v.16 no.6
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• pp.303-316
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• 2023

Using industrial wastes and construction and demolition (C&D) wastes is potentially advantageous for concrete production in terms of sustainability improvement. In this paper, a sustainable Self-Compacting Concrete (SCC) made with industrial wastes and C&D wastes was proposed by considerably replacing natural counterparts with recycled coarse aggregates (RCAs) and supplementary cementitious materials (SCMs) (i.e., Fly ash (FA), ground granulated blast furnace slag (GGBS) and silica fume (SF)). A total of 12 SCC mixes with various RCAs and different combination SCMs were prepared, which comprise binary, ternary and quaternary mixes. The mechanical properties in terms of compressive strength and static elasticity modulus of recycled aggregates (RA-SCC) mixes were determined and analyzed. Microstructural study was implemented to analyze the reason of improvement on mechanical properties. By means of life cycle assessment (LCA) method, the environmental impacts of RA-SCC with various RCAs and SCMs were quantified, analyzed and compared in the system boundary of "cradle-to-gate". In addition, the comparison of LCA results with respect to mechanical properties was conducted. The results demonstrate that the addition of proposed combination SCMs leads to significant improvement in mechanical properties of quaternary RA-SCC mixes with FA, GGBS and SF. Furthermore, quaternary RA-SCC mixes emit lowest environmental burdens without compromising mechanical properties. Thus, using the combination of FA, GGBS and SF as cement substitution to manufacture RA-SCC significantly improves the sustainability of SCC by minimizing the depletion of cement and non-renewable natural resources.

• Journal of the Korean GEO-environmental Society
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• v.25 no.7
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• pp.5-19
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• 2024

During the blasting process, a fracture zone is formed in the vicinity of the blast hole. Any damage that extends beyond the excavation boundary line necessitates the implementation of an additional support system to assure safety. Typically, fracture zone radius is estimated from blast hole pressure using theoretical methods due to its simplicity. However, linear charge concentration (kg/m) is used for tunnel blasting. This paper compiles Swedish experimental datasets to estimate the radius of fracture zones based on linear charge concentration. Further numerical analyses are performed in LS-DYNA for coupled single-hole blasting. The Riedel-Hiermaier-Thoma (RHT) model has been selected as the constitutive model for this investigation. The numerical model is validated against small-scale laboratory tests. Parametric studies are conducted to predict fracture zones in granite and sandstone rocks using two kinds of explosives, PETN and AFNO. The analyses evaluate ten types of blast hole sizes, ranging from 17 to 100 mm. The results indicate that granite has a larger fracture zone than sandstone, and the PETN explosive predicts more damage than ANFO. Smaller blast holes exhibit smaller fracture zones in comparison to larger blast holes. Wave propagation is more rapidly attenuated in granite than in sandstone. Subsequently, the predicted fracture zone outcomes are compared with the empirical dataset. Fracture zones of medium blast hole diameter align well with the experimental data set. A predictive equation is derived from the data set, which may be used to evaluate blast design to manage fracture zones beyond the excavation line.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.3
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• pp.685-692
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• 2024

Currently used heating elements are metal and non-metal heating elements, including various types of heaters, and resistance line heating elements have a problem of decreasing thermal efficiency over time, so to solve this problem, a planar heating element using high-purity carbon materials and oxidation-resistant inorganic compounds was applied. Through the manufacture of planar heating elements using CNT, ruthenium composite materials, and ruthenium oxide, physicochemical performance and capacity were increased, and instantaneous responsiveness was increased. Through thick film technology applicable to various base bodies, fine patterns were formed by the screening method in consideration of the fact that the performance of the heat source depends on the viscosity and pattern shape. The heating element was manufactured by thick film printing technology by mixing ruthenium oxide, CNT, Ag, etc. The characteristics of each paste were analyzed through viscosity measurement, and STS 430 was used as a base. Surface temperature and efficiency were measured by testing heaters manufactured for small wind tunnels and real-vehicle experiments. The surface temperature decreased as the air volume increased, and the optimal system boundary was found to be about 200 mm. Among the currently used heating elements, this paper manufactured a planar heating element using thick film technology to find out the relationship between air volume and temperature, and to study the surface temperature.

• The Journal of the Petrological Society of Korea
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• v.20 no.2
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• pp.77-98
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• 2011

The igneous complex consisting of mangerite and gabbro in the Odaesan area, the eastem part of the Gyeonggi Massif, South Korea, intruded early Paleo-proterozoic migmatitic gneiss. The mangerite is composed of orthopyroxene, clinopyroxene, amphibole, biotite, plagioclase, pethitic K-feldspar, quartz. The gabbro has similar mineral assemblage but gabbro has minor amounts of amphibole and no perthitic K-feldspar. The gabbro occurs as enclave and irregular shaped body within the mangerite, and the boundary between the mangerite and gabbro is irregular. Leucocratic lenses with perthitic K-feldspar are included in the gabbro enclaves. These textures represent mixing of two different magmas in liquid state. SHRIMP U-Pb zircon age dating gave $234{\pm}1.2$ Ma and $231{\pm}1.3$ Ma for mangerite and gabbro, respectively. These ages are similar with the intrusion ages of post collision granitoids in the Hongseong (226~233 Ma) and Yangpyeong (227~231 Ma) areas in the Gyeonggi Massif. The mangerite and gabbro are high Ba-Sr granites, shoshonitic and formed in post collision tectonic setting. These rocks also show the characters of subduction-related igneous rock such as enrichment in LREE, LILE and negative Nb-Ta-P-Ti anomalies. These data represent that the mangerite and gabbro formed in the post collision tectonic setting by the partial melting of an enriched lithospheric mantle during subduction which occurred before collision. The heat for the partial melting was supplied by asthenospheric upwelling through the gab between continental and oceanic slabs formed by slab break-off after continental collision. The distribution of post-collisional igneous rocks (ca. 230 Ma) in the Gyeonggi Massif including Odaesan mangerite and gabbro strongly suggests that the tectonic boundary between the North and South China blocks in Korean peninsula passes the Hongseong area and futher exteneds into the area between the Yangpyeong-Odaesan line and Ogcheon metamorphic belt.

• Korean Journal of Remote Sensing
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• v.33 no.6_1
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• pp.981-992
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• 2017

We, for the first time, retrieved tropospheric nitrogen dioxide ($Trop.NO_2$) vertical column density (VCD) from ground-based instrument, Pandora, using the optical density fitting based on Differential Optical Absorption Spectroscopy (DOAS)in Seoul for the period from May 2014 to December 2014. The $Trop.NO_2$ VCDs retrieved from Pandora were compared with those obtained from Ozone Monitoring Instrument (OMI). A correlation coefficient (R) between those retrieved from Pandora and those obtained from OMI is 0.55. To compare with surface $NO_2$ VMRs obtained from in-situ, Trop. $NO_2$ VCDs retrieved from Pandora and those obtained from OMI are converted into $NO_2$ VMRs in boundary layer (BLH $NO_2$ VMRs) using data measured from Atmospheric Infrared Sounder (AIRS). Surface $NO_2$ VMRs obtained from in-situ range from 5.5 ppbv to 61.5 ppbv. BLH $NO_2$ VMRs retrieved from Pandora and OMI range from 2.1 ppbv to 44.2 ppbv and from 0.9 ppbv to 11.6 ppbv, respectively. The range of BLH $NO_2$ VMRs retrieved from OMI is narrower than that of BLH $NO_2$ VMRs retrieved from Pandora and surface $NO_2$ VMRs obtained from in-situ. There is a batter correlation between surface $NO_2$ VMRs obtained from in-situ and BLH $NO_2$ VMRs retrieved from Pandora (R= 0.50)than the correlation between surface $NO_2$ VMRs obtained from in-situ and BLH $NO_2$ VMRs retrieved from OMI (R = 0.36). This poor correlation is thought to be due to the lower near-surface sensitivity of the satellite-based instrument (OMI) than Pandora, the ground-based instrument.

• Journal of the Korean earth science society
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• v.40 no.6
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• pp.584-598
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• 2019

In this study, the effects of air-sea interactions on precipitation over the Seoul-Gyeonggi region of the Korean Peninsula from 28 to 30 August 2018, were analyzed using a Regional atmosphere-ocean Coupled Model (RCM). In the RCM, a WRF (Weather Research Forecasts) was used as the atmosphere model whereas ROMS (Regional Oceanic Modeling System) was used as the ocean model. In a Regional Single atmosphere Model (RSM), only the WRF model was used. In addition, the sea surface temperature data of ECMWF Reanalysis Interim was used as low boundary data. Compared with the observational data, the RCM considering the effect of air-sea interaction represented that the spatial correlations were 0.6 and 0.84, respectively, for the precipitation and the Yellow Sea surface temperature in the Seoul-Gyeonggi area, which was higher than the RSM. whereas the mean bias error (MBE) was -2.32 and -0.62, respectively, which was lower than the RSM. The air-sea interaction effect, analyzed by equivalent potential temperature, SST, dynamic convergence fields, induced the change of SST in the Yellow Sea. In addition, the changed SST caused the difference in thermal instability and kinematic convergence in the lower atmosphere. The thermal instability and convergence over the Seoul-Gyeonggi region induced upward motion, and consequently, the precipitation in the RCM was similar to the spatial distribution of the observed data compared to the precipitation in the RSM. Although various case studies and climatic analyses are needed to clearly understand the effects of complex air-sea interaction, this study results provide evidence for the importance of the air-sea interaction in predicting precipitation in the Seoul-Gyeonggi region.

• Environmental and Resource Economics Review
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• v.23 no.4
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• pp.719-746
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• 2014

This study attempts to estimate the value of the water quality improvement by deriving the equilibrium price of the water pollutant emission permit for the imaginary water pollutant emission trading market. It is reasonable to say that there is already an implicit social agreement for the unit value of water pollutant, when the government set the Total Water Pollutant Loading System for the major river basin as a part of the Comprehensive Measures for Water Management, particularly for the Nakdong River Basin. Therefore, we can derive the unit value of water pollutant emission, which is already implied in the pollution allowance for each city or county by the Total Water Pollutant Loading System. Once estimated, it will be useful to the economic assessment of the water quality related projects. An imaginary water pollutant emission trading system for the Nakdong River Basin, where Total Water Pollutant Loading System is already effective, is constructed for the estimation of the equilibrium price of water pollutant permit. By estimating marginal abatement cost curve or each city or county, we can compute the equilibrium price of the permit and then it is regarded as the economic value of the water pollutant. The marginal net benefit function results from the relationship between the emission and the benefit, and then the equilibrium price of permit comes from constructing the excess demand function of the permit by using the total allowable permit of the local government entity. The equilibrium price of the permit would be estimated to be $1,409.3won/kg{\cdot}BOD$. This is within reasonable boundary compared for the permit price compared to foreign example. This permit price would be applied to calculate for the economic value of the water quality pollutants, and also be expected to use directly for the B/C analysis of the business involved with water quality change.

• Journal of the Korean Geographical Society
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• v.40 no.3 s.108
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• pp.253-273
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• 2005

In recent years, there are strong social demands to characterize the spatial distribution of mountains in Korea. This study aims to develop a 'Sanjulgi-Jido(mountain ridge map)' that might be used not only to satisfy these social demands but also to effectively present the spatial distribution of mountains and drainage basins in the Korean Peninsular. The 'Sanjulgi-Jido' developed in this study is a map that presents the continuity of mountains based on the drainage divides that are delineated by a pre-defined drainage basin size and elevation. This study first validated the Bakdudaegan system through the analyses of a digital elevation model. The Bakdudaegan system has long been recognized as the Koreans traditional conceptual framework to characterize the spatial distribution of mountains. The analyses showed that the Bakdudaegan system has several problems to represent the mountain systems in Korea, which includes 1) the lack of the representativeness of drainage basins, 2) inaccuracy to depict the boundary of drainage basins, 3) the lack of representativeness of mountains, and 4) geo-polical issue that confines the spatial extent of mountain systems within the Korean Peninsular. In order to represent the mountains system in a more quantitative manner, we applied several terrain analysis techniques to understand the spatial distribution of mountains and drainage basins. Based on these analyses, we developed an hierarchical system to classify the continuity (If mountains, which are presented as the spatial distribution of drainage divides with a certain elevation. The first-order Sanjulgi is the drainage divides whose drainage basin are bigger than $5,000km^2$ and the point elevation is above 100m. The next order Sanjulgi is delineated as the size of drainage basin is successively divided by two. This kind of design is able to provide a logical framework to present the mountain systems at different details, depending on the purpose and scale of maps. We also provide several empirical functions to calculate various geomorphological indices for each order of Sanjulgi. The 'Sanjulgi Jido' is similar with the Bakdudaegan system, since it characterizes the continuity of mountains based on the spatial distribution of the drainage divide. It, however, has more scientific criteria to define the scale and continuity of mountains. It should be also noted that the 'Sanjulgi Jido' proposed has different logical and methodological background, compared with the mountain range map that explains the genesis of mountain systems in addition to the continuity of mountains.