• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.135-148
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• 2014

This study was performed to evaluate the performance about Improved C12A7 based mineral accelerator (ICM) increased in initial and long-term strength. ICM was developed to overcome the long-term strength decrease in existing accelerator. To evaluate the performance of ICM according to addition rate, setting time, compressive strength, and flexural strength tests were conducted in laboratory. In results, initial setting time was slower, final setting time was faster than existing $C_{12}A_7$ based mineral accelerator (CM) when usage of ICM 6%. In compressive and flexural strength, existing CM was higher than ICM at 3hours and 1day. After 7days, strength of shotcrete using ICM was increased. Rebound test, compressive strength and flexural strength test with optimum addition rate through the laboratory test were conducted in field. Field experiment results were the same as laboratory test. Long-term strength performance of ICM was superior to existing accelerator.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.4
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• pp.635-650
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• 2017

Acoustic emission (AE) sensors have broadly used to monitor the damage of underground structures and tunnels. The reliability of measured signal is determined by the coupling condition of the AE sensors which are embedded in the target underground structure. To secure the reliability of health monitoring results, it is important to understand the characteristics of the coupling materials. In this study, laboratory tests were performed using portland cement, micro cement, and gypsum as coupling materials in order to verify the bleeding characteristics. The effective parameters for bleeding were determined to be water-cement ratio, material type, curing time, and injected volume of coupling materials. As a results of the experimental study, the bleeding rate increases with an increase in a water-cement ratio and an injected volume; for portland cement, water-cement ratio and injected volume effects are larger than the micro cement. However, curing time is not much effective for occurrence of the bleeding phenomenon. It is anticipated that this study may be useful for the selection of suitable coupling materials for installation of acoustic emission sensors.

• The Journal of the Petrological Society of Korea
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• v.18 no.1
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• pp.49-65
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• 2009

Endlessly, mankind has been pursuing its dream toward understanding and conquering our neighboring planet, Mars since Mars has been identified as a planet. After the development of advanced science and technology of human race in 1960, the Union of Soviet Socialist Republics (USSR) had initiated its dream toward Mars and finally at present mankind acquires numerous important clues of Mars through over forties of space programs toward Mars. Furthermore, mankind takes its effort in colonizing Mars within several decades. This manuscript introduces the history of space mission programs of Mars up to date and major scientific findings to understand the Mars.

• 한국지구물리탐사학회:학술대회논문집
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• 2011.10a
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• pp.143-144
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• 2011

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.6
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• pp.519-526
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• 2018

In order to analyze space resources, it had to be brought to earth. However, using laser-induced breakdown spectroscopy(LIBS) and Raman spectroscopy, it is possible to analyze qualitative and quantitative analysis of space minerals in real time. LIBS is a spectroscopic method in which a high energy laser is concentrated on a material surface to generate a plasma, and the emitted light is acquired through a spectroscope to analyze the atomic composition. Raman spectroscopy is a spectroscopic method that analyzes the molecular structure by measuring scattered light. These two spectroscopic methods are complementary spectroscopic methods for analyzing the atoms and molecules of unknown minerals and have an advantage as space payloads. In this study, data were analyzed qualitatively by using principal component analysis(PCA). In addition, a mixture of two minerals was prepared and a quantitative analysis was performed to predict the concentration of the material.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.315-328
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• 2004

In this paper, we present a good example of extreme solar and geomagnetic activities from October to November, 2003. These activities are characterized by very large sunspot groups, X-class solar flares, strong particle events, and huge geomagnetic storms. We discuss ground-based and space-based data in terms of space weather scales. Especially, we present several solar and geomagnetic disturbance data produced in Korea : sunspots, geo-magnetograms, aurora, Ionogram, and Total Electron Content (TEC) map by GPS data. Finally, we introduce some examples of the satellite orbit and communication effects caused by these activities; e.g., the disturbances of the KOMPSAT-1 operational orbit and HF communication.

• Tunnel and Underground Space
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• v.24 no.6
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• pp.449-463
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• 2014

There are many case studies and application cases in abandoned mines for hydraulic filling method filled by slurry or paste form, but research on the pneumatic filling is not applied in Korea. The damage of steel pipe is occurred by wear due to the flow of filling material in the bent area of steel pipe in traditional pneumatic filling method. In this study, the new pneumatic filling method was developed using a newly devised improved nozzle to improve the above problem. The model test for mine filling was performed in the laboratory for the simulated accessible or inaccessible mine cavities, and the filling efficiency by the results obtained from the test was calculated. The filling efficiency was analyzed from the variation of outlet angle, feed rate and grain size of sand in model test of simulated accessible mine cavity. The superiority of improved pneumatic filling method was proved through the analysis of filling efficiency by the results obtained from each model tests of gravitational, traditional, and improved filling method in simulated inaccessible mine cavity.

• Economic and Environmental Geology
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• v.48 no.4
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• pp.325-335
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• 2015

This study examined the possibility to extract potential alteration zones and lithologic information based on ASTER band ratio techniques for mineralized area located in ${\ddot{O}}v{\ddot{o}}rkhangai$ province, Mongolia, and the effectiveness of remote sensing as a preliminary exploration tool for mineral exploration was tested. The results of ABRLO, PBRLO, and PrBRLO models indicated that the detection of argillic zone requires the verification of the samples to verify hydrothermal alteration minerals as clay minerals can formed by weathering process, whereas phyllic-propylitic zones were considerably related to the spatial distribution of the intrusive bodies, geological structures, and ore distribution. QI and MI results showed that QI is more useful for sedimentary rocks such as conglomerate and sandstone than meta-sedimentary like quartzite, and MI faced relatively uncertain in detection of felsic or mafic silicate rocks. QI and MI may require additional geologic information such as the characteristics of samples and geological survey data to improve extraction of lithologic information, and, if so, it is expected that remote sensing technique would contribute significantly as a preliminary geological survey method.

• Economic and Environmental Geology
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• v.48 no.5
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• pp.421-429
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• 2015

Base researches in geoscience and mineral resources, such as geological and geo-thematic mapping, geological survey and observation, have long-term, continuity and time-leasing characteristics and they are difficult to present the particular research stages or progressions in the research span. The Technology Readiness Levels (TRLs), developed by the U.S. National Aeronautics and Space Administration (NASA), is effective for presenting research maturity levels and progression in the development of new technologies. This study suggests adjusted definitions for the Technology Readiness Levels to fit Geo-technology (Technology in Geoscience and Mineral Resources). Base geological researches, including mapping, surveys and observation, can be also presented in research levels from TRL 1 (R&D planning, literature survey) to TRL 9 (geological information construction and service in all target areas) in terms of the final product's coverage. Moreover, not only development and construction of commercial products, geological disasters and environmental researches can also be presented in field demonstrations through public pilot applications. The modified commercialization or cemonstration TRLs in Geo-technology are TRL 5 (starting pilot field application), TRL 6 (pilot field operation) and TRL 7 (pilot field operation for a larger scale, greater than ten percent of the actual environment).

• Korean Journal of Mineralogy and Petrology
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• v.36 no.2
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• pp.125-134
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• 2023

The Naedeokri and Nonggeori granites are early Proterozoic granites of the Taebaek-Sangdong area in the northeastern part of the Yeongnam Massif. In this paper, rare earth elements (REEs) concentrations of the minerals in Naedeokri and Nonggeori granites and Rb-Sr mineral isochron age are reported. Except zircon, the constituent minerals such as mica, feldspar, quartz, and tourmaline show LREE-enriched and HREE-depleted REE patterns with relatively large Eu negative anomaly. However, zircon has geochemical characteristic of LREE- and HREE-enriched REE pattern with large Eu positive anomaly. This pattern suggests that zircon should be hydrothermal zircon due to deuteric hydrothermal alteration. In addition, the Rb-Sr mineral age of Naedeokri granite indicates an age value of 1.814±142(2σ) Ma. The Rb-Sr whole rock age including pervious data of Naedeokri and Nogggeori granite indicates an age value of 1,707±74(2σ) Ma. This value is younger than the Sm-Nd isochron of 1.87 Ga, indicating that the Rb-Sr isotope system may be re-homogenized by hydrothermal alteration during the transition from a magmatic to a hydrothermal system.