• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.2
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• pp.33-56
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• 2001

It is well known fact that all rocks exhibit brittle properties and time depends strain properties (creep). An understanding of the time dependent deformation behaviour of rocks is believed to be essential in the field of civil and tunnelling. The rock and concrete creep in various forms of loading conditions and physical environment are reviewed. A comparison of creep behaviour between rocks and concrete is provided, in order to bring two existing relatively independent methods of predicting creep strain closer together. It was felt that the physical process in the creep of rocks would be similar to the process in creep of concrete. Since experiments and observations have shown that non-elastic (creep) mechanical behaviour of all crystalline solids (i.e., concrete, rocks, ceramics and refractories) and single materials have a common base. Also a comparison of the results for the accepted methods of estimating creep in rocks and concrete under - multiaxial loading was attempted to extend the knowledge of deformational characteristics of these two materials.

• Journal of the Korean Ceramic Society
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• v.17 no.2
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• pp.96-100
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• 1980

The castable refractory, CaO.$2Al_2O_3$ is a useful alumina cement for iron, steel and cement for iron, steel and cement industries, however it is difficult to produce CaO.$2Al_2O_3$because of its high melting point(180$0^{\circ}C$) and narrow firing range. In this study, the coprecipitation method was used to produce CaO.$2Al_2O_3$ for lower temperature firing . This method involved the titration of mixed solution of calicum and aluminate which extracted from domestic kaolin with $NH4_OH$ solution under blowing $CO_2$ gas into the solution. The coprecipitate and its clacined products were analyzed by X-ray diffraction and DTA. The calcined products fired between 400 and 90$0^{\circ}C$ were amorphous, but at 100$0^{\circ}C$ the coprecipitate was converted into one compound, CaO$2Al_2O_3$. From those experimental results, it was found that we could synthesizze CaO.$2Al_2O_3$ at about 100$0^{\circ}C$ which is lower than conventional firing temperature by around 80$0^{\circ}C$. The refractoriness of this alumina cement was SK 34 and the compressive strength ( 1 day) was about 250kg/$\textrm{cm}^2$.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.5
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• pp.483-490
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• 2009

The objective of this development project is to localize an automatic molten metal supplier that has been distributed by WESTOMAT, Germany, throughout the world. To achieve this purpose, an energy-saving pressurized dosing furnace and molten metal differential pressure control system that Is able to automatically supply a determined quantity of aluminum molten metal were developed. The localized equipment was installed in a site. Also, the results of the test operation of this equipment can be summarized as follows: It was able to improve the productivity because there were small decreases in supplying speeds and small losses in wastes compared to the existing mechanical molten metal supplier. Also, it was able to minimize the cost in maintenances due to the direct application of high temperature molten metals to molds. In addition, there were small energy losses due to the use of high thermal insulators compared to the existing reverberating furnace and able to prolong the life-time of furnaces and produce good quality nonferrous metals because it represented small carbon refractories and alumina in applied molten metals. Furthermore, it demonstrated no particular differences by objectively comparing it with the product by WESTOMAT.

• Journal of Korean Institute of Industrial Engineers
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• v.21 no.4
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• pp.581-591
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• 1995

The main objective of this study is to compare three representative methods predicting compressive forces on lumbosacral disc : LP-based method, double LP-based method and EMG-assisted method. Two subjects simulated lifting tasks performed in the refractories industry, in which vertical and horizontal distance, and weight of load were varied. To calculate the L5/S1 compressive forces, EMG signals from six trunk muscles were measured and postural data and locations of load were recorded using the Motion Analysis System. The EMG-assisted model was shown to reflect well all three factors considered here. On the other hand, the compressive forces of the LP-based model and the double LP-based model were only significantly affected by weight of load. In addition, lowly positive correlation was observed between compressive forces of the EMG-assisted model and lifting index(LI) of 1991 NIOSH lifting equation. From this results, it can be concluded that compressive forces on L5/S1 by the EMG-assisted method should be used as biomechanical criterion in order to evaluate risk of jobs precisely, and LI can not evaluate risk of lifting tasks fully.

• Membrane and Water Treatment
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• v.10 no.6
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• pp.451-460
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• 2019

Thin film composite membranes incorporated with nano-sized hydrophilic zeolite -A were successfully prepared via interfacial polymerization (IP) on porous blend PES/PAN support for water desalination. The thin film nanocomposite membranes were characterized by SEM, contact angle and performance test with 7000 ppm NaCl solution at 7bar. The results showed that the optimum zeolite loading amount was determined to be 0.1wt% with permeate flux 29LMH.NaCl rejection was improved from 69% to 92% compared to the pristine polyamide membrane where the modified PA surface was more selective than that of the pristine PA. In addition, there was no significant change in the permeate flux of the thin film nanocomposite membrane compared with that of the pristine PA in spite of the formation of the dense polyamide layer. The stability of the polyamide layer was investigated for 15 days and the optimized membrane presented the highest durability and stability.

• Resources Recycling
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• v.30 no.1
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• pp.3-13
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• 2021

In the secondary refining process for the production of high-grade steel, the proper composition is maintained by alloying elements, and non-metallic inclusions are controlled for high cleanliness. Complex reactions occur simultaneously between the molten steel, slag, inclusions, refractories, and alloying elements during the secondary refining process. Previous works have reported simulation models based on kinetics to predict the compositional changes in molten steel, slag, and inclusions in actual processes. Analytical reviews are required for the models to predict the process accurately. In this study, we reviewed and analyzed simulation models based on the coupled reaction model for the secondary refining process.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.60.4-60.4
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• 2019

Small bodies in the solar system are pristine leftovers of planetesimals since the formation epoch (~4.6 Gyr ago). After the formation, icy planetesimals have been preserved in the distant cold place beyond 30 au (i.e., Trans-Neptunian region) until recently without any catastrophic processes but have just been injected into inner region (<~5 au from the Sun) to be observed as comets. On the contrary, asteroids are rocky primitive objects (although some of them contains icy volatiles) distributing in the mainbelt between Mars and Jupiter orbits. Because of frequent encounters in the mainbelt, asteroids have experienced a number of repeated impacts until the present day. Namely, it is important to investigate thermal alternation process of cometary volatiles and refractories in the solar radiation field, whereas collisional and subsequence phenomena of asteroidal bodies. Although recent spacecraft observations revealed the physical natures on the surfaces of comets and asteroids, their interiors still remain largely unexplored. It is likely that a sudden brightening of a comet is associated with rapid sublimation of internal CO and CO2 or phase transition of amorphous H2O. An episodic dust ejection from an asteroid is causally related to an impact among asteroids, sudden sublimation of remaining subsurficial volatiles, etc. Because these transient phenomena provide rare opportunities to investigate their interiors, immediate observations using any optical instruments are particular important. In my presentation, I will review some examples of such transient phenomena in the solar system and propose possible collaborative research using the Korean Small Telescope Network.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.3
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• pp.481-486
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• 1997

It was succeeded in synthesizing the $Al_2O_3$-SiC refractory powders, which is main raw material of AlSiCa, from the domestic Hadong Kaolin. The oxidation reaction of the synthesized $Al_2O_3$-SiC powder was examined. The activation energy for SiC in $Al_2O_3$-SiC powder was calculated to be $\Delta$G=74.86 KJ/mol in air, however the poor sinterability of the powders is thought to be due to the vaporization of SiC in $H_2$ atmosphere. The formation of the whisker-SiC gives the possibility in use for high temperature structural material over high temperature refractory brick.

• Resources Recycling
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• v.13 no.3
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• pp.50-57
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• 2004

Waste aluminum dross is a major waste in the aluminum scrap smelters and its components are mostly alumina and remained metallic aluminum. In the process to extract the remained aluminum from the waste dross by leaching with sodium hydroxide solution, residue is generated and its main component is alumina. This residue could be recycled into ceramic materials such as alumina castable refractories by going through a series of treatments such as washing, drying and roasting. In this study, a pilot plant was constructed and tested to demonstrate the developed technology. One thousand tons of waste aluminum dross could be processed, and about seven hundred tons of ceramic materials produced in the demonstration line. From the test run of the pilot plant, although it was confirmed that the developed technology could be applied to commercialization, several technical improvements were found to be necessary for reducing impurities such as Na, Fe and for reforming drying equipment.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.3
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• pp.60-67
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• 2010

Korea's large-scale incinerating facilities of domestic waste were built in the late 1980's. It was found that most of the incinerators were designed during the period and even the ones constructed afterwards have been built without any changes or modifications. However, the nature of waste fed into incinerators is undergoing a radical change due to government policies on waste collection, which is upheld by a research into changes in the heating value of domestic wastes. As a result, refractories and stokers are being damaged in many of the facilities due to overheating. On the other hand, the formation of clinkers on boilers' heating surface, which curbs he at transfer, results in problems such as a fall in used heating value and a rise in the temperature of combustion chambers. Methods are being deployed to resolve the problems-such as spraying water on piles of waste, incinerating food waste by mixing together what has been separately collected, spraying water on combustion chambers, etc. Such actions are not a fundamental solution, nor redesigning and rebuilding incineration facilities is cost-effective. This research seeks to develop a fundamental solution to address the situation.