• The Journal of Engineering Geology
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• v.17 no.2 s.52
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• pp.225-233
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• 2007

The engineering properties of surface soils in natural terrain are changed due to wildfire. This change of engineering properties induced by wildfire is related to landslides occurrence. To investigate the change of soil properties caused by wildfire, the various soil tests are performed. The soil samples are obtained from the recently burned slopes of Yangyang area, Kangwon Province. The soil samples obtained from the burned slopes are classified into three types depending on the burning grade: the perfect burning grade, the intermediate burning grade, the non-burning grade. As the result of tests, the specific gravity and the dry unit weight of soils obtained from perfect and alternative burning grades are less than those of soils obtained from non-burning grade. It judges that an electronic force, ionic components and of soils are changed and organic matters in soils are burned by wildfire. The permeability of soil obtained from alternative burning grade is the lowest and that of soil obtained from perfect burning grade is the highest. The water-repellent layer is formed on soil surface by wildfire. The water-repellent layer is existed at the area of alternative turning grade, while the layer is not existed at the area of perfect burning grade. The water-repellent layer is collapsed in high temperature more than about $400^{\circ}C$.

• The Journal of Korean Obstetrics and Gynecology
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• v.19 no.3
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• pp.203-213
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• 2006

Purpose : This study was carried out to evaluate correlation between Bone Mineral Density(BMD) and degenerative lumbar disease in postmenopausal low back pain patients. Methods : 69 postmenopausal patients with low back pain were examined. Magnetic resonance imaging was performed to evaluate degenerative lumbar disease and bone mineral density of lumbar spine was measured by Dual energy X-ray absorptiometry. Data were analyzed by Pearson's Linear Correlation Coefficient. Results : In postmenopausal patients with low back pain, BMD(T-score, Z-score) had negative correlation with the grade of intervertebral disc herniation and positive correlation with weight. Other lumbar diseases including Spinal stenosis, Spondylolisthesis and Facet joint arthrosis didn't have significant correlation with BMD. Conclusion : In postmenopausal patients with low back pain, BMD(T-score, Z-score) had inverse relationship with the grade of intervertebral disc herniation.

• Mineral and Industry
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• v.28
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• pp.1-13
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• 2015

In this study, it was carried out separation process research and development to be able to produce high-grade tungsten concentrate form tungsten taken form Mongolia. In order to reduce treatment cost and increase separation efficiency the jig separation at first was applied for recovering the concentrate. Which reground would make the degree of liberation increase. Which was treated by shaking table to reject the gangue minerals from the first concentrate. Because the heavier product contains not only ferberite but also cassiterite, the product was treated by further dry magnetic separation to obtain the ferberite concentrate. Finally, the high-grade ferberite concentrate of 67.63% $WO_3$ could be obtained with recovery of 86.07% through the separation process developed in this study.

• Tribology and Lubricants
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• v.28 no.2
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• pp.81-92
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• 2012

To product multi-grade oil like engine oil, a sort of mineral base oil is mixed with a fundamental additive liquid package and a polymer liquid as viscosity index improver in order to improve the lubricating property of oil. That is, engine oil is the mixture of more than two fluids. In this paper, it will be systematically organized the governing equation describing non-Newtonian thermo-hydrodynamic lubrication related with the mixture of incompressible fluids based on the principle of continuum mechanics. Then, in order to find how the thermal analysis effect on the bearing performance lubricated with the mixture of multi-fluids, it will be compared to the performances between the mixture of each liquid to be blended and multi-grade engine oil as a single fluid in a high speed journal bearing. It is found that, in the case of lower viscosity oil, the difference of pressure distribution between the above two cases turns out to be existed, even if the load capacity is same level.

• Korean Journal of Materials Research
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• v.19 no.4
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• pp.212-219
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• 2009

A study on the dry beneficiation of sericite occurring in the Daehyun Mine of the Republic of Korea region as performed by applying selective grinding and air classification techniques. Quartz and sericite occurred in the raw ore as major components. The results of liberation using a ball mill and an impact mill showed that the contents of $R_2O$ were increased while $SiO_2$ was decreased in proportion to decreasing particle size. According to the XRD, XRF analysis and the EDS of SEM analysis, the ball mill gave a better grade product in $R_2O$ content than the impact mill when the particle size was the same. When the raw ore was ground by the impact mill with arotor speed 57.6 m/sec and then followed by 15,000rpm classification using an air classifier, the chemical composition of the over flowed product was 49.65wt% $SiO_2$, 32.15wt% $Al_2O_3$, 0.13wt% $Fe_2O_3$, 10.37wt% $K_2O$, and 0.14wt% $Na_2O$. This result indicates that the $R_2O$ contents were increased by 49.5% compared to that of the raw ore. From these results described above, it is suggested that hard mineral such as Quartz little ground by selective grinding using impact mill whereas soft mineral such as sericite easily ground to small size. As a result of that hard minerals can be easily removed from the finely ground sericite by air classification and the $R_2O$ grade of thus obtained concentrate was improved to higher than 10wt% which can be used for ceramics raw materials.

• Journal of the Korean Ceramic Society
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• v.51 no.2
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• pp.72-81
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• 2014

The main mineral phases of natural hydraulic lime (NHL) as a hydraulic lime binderare $Ca(OH)_2$, $C_2S$, $C_3S$, $C_3A$, and $SiO_2$ residues. Also, NHL has the characteristic of setting and hardening by a hydration reaction with water and by carbonation reactions with carbon dioxide from the air. In this study, in an effort to investigate changes of the mineral phases by NHL hydration and carbonation reactions, transitions of mineral phases and the microstructures of hardened pastes were analyzed by XRD, DSC, SEM, and by pore size distributions using domestic and foreign-sourced NHL pastes after curing at 1, 3, 7, and 28 days. On the basis of the analysis results, it was confirmed that domestic low-grade limestone can be used for the manufacturing of NHL. The main hydration mineral phases were $Ca(OH)_2$, $CaCO_3$, $C_2S$, and $SiO_2$ residues, while in the case of foreign-sourced NHL, a small amount of an aluminium hydration phase formed. Also, the $CaCO_3$ content after the carbonation reaction increased with an increase in the curing time. After hydration for 28 days, NHL containing considerable amounts of $C_2S$ and $C_3S$ showed higher carbonation ratios than others types.

• Mineral and Industry
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• v.26
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• pp.13-21
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• 2013

This study is carried out experiments on various factors for improving the grade of low grade scheelite by Knelson concentrator prior to the main beneficiation process. Even though there are several gravity separators such as Jig, Spirals and etc. for rougher concentrate, the KC3 Knelson Concentrator was adopted to get better separation efficiency and beneficiating effects for pre-concentration of the low grade scheelite ore. The feed samples was prepared to minus 1mm in size by crushing and grinding. The important factors in the KC3 Knelson Concentrator test were examined in terms of the variations such as number of treatment, feed rate, rotation speed of bowl(G force), water flow rate, pre-removal of magnetic minerals, feed size and feed grade. According to the result of experiment, it shows that the important technical variations are limited in terms of number of treatment, feed rate, feed size and feed grade. The final result shows that the KC3 Knelson Concentrator obtains the scheelite pre-concentrate of about $3%WO_3$ grade and 90% recovery, respectively, from the feed containing about $0.8-1.0%WO_3$ grade.

• Economic and Environmental Geology
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• v.47 no.2
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• pp.169-180
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• 2014

Surface geological and trench surveys and drilling exploration (total length, 1,100 m; 9 drill holes) were carried out to secure new Au ore bodies in the area($0.96km^2$) of Actosity gold field, where is located at the western Kuldjuktau mineralized district in the middle territory of Uzbekistan. Several Au ore bodies occurring as tabular or lens shapes with thickness of 0.5~35 m were newly discovered on the outcrops and extended to $N40{\sim}70^{\circ}\;W$ direction with dipping of $70{\sim}90^{\circ}$ SW or NE. Indicated ore resource of gold with Au grade of 0.25~3.52 mg/kg was newly estimated by 2,382 t(gold resource of 2.5 t) as a result of 9 drilling exploration in 2010~2012 from the Actosity gold field. Judging from the ore resources and Au grade of the Actosity gold field, economic potentiality of mining development seems to be low. Because of high possibility to secure new ore resources through more detailed exploration works from the Actosity area, the growth of econonic value will be expected by a mine of middle scale.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.4
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• pp.375-385
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• 2013

This study evaluates correlation between petrographic characteristics and weathering grade of low-graded metasedimentary rocks mainly consisting of phyllite. Weathering grade of rock material was determined based on the results of geological survey. The Schmidt hammer test was carried out to obtain estimates of strength of rock materials. Point counting and microscopic observation were also conducted to analyze mineral composition and to measure spacing of foliation for 9 rock specimens. As a result of microscopic analysis, as the weathering grade was lower, the quartz was found more in quantity, consequently making rock stronger against weathering process. On the other side, lower weathering grade of rock resulted in less content of mica which is weak against weathering process. In addition, the rock materials with closer foliation spacing are found to be weaker in strength and have higher weathering grade.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.160-165
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• 2008

Kriging interpolation technique has been proposed by Danny Krige of South Africa to find the mineral distribution grade from information of geography and space. It is one of the generally used prediction technique for the mineral distribution grade and underground water level in wide scope also used in computer graphics fields by the ability for the surface regeneration This paper comprises two specific objectives. The first is to examine the applicability of Ordinary Kriging interpolation(OK) to finite element method that is based on variogram modeling in conjunction with different allowable limits of separation distance. The second is to investigate the accuracy according to theoretical variogram such as polynomial, Gauss, and spherical models.