• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.193-197
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• 2001

This study was carried out to recover gold, silver and other valuable metals from the printed circuit boards (PCB) of waste computers. PCB samples were crushed to under 1mm by a shredder and initially separated into 30% conducting and 70% non-conducting materials by an electrostatic separator. The conducting materials, which contained the valuable metals, were then used as the feed material for magnetic separation where it was found that 42% was magnetic and 58% non- magnetic. The non-magnetic materials contained 0.227mg/g Au and 0.697mg/g Ag. Further leaching of the non-magnetic component using 2.0M sulfuric acid and 0.2M hydrogen peroxide at 85$^{\circ}C$ extracted more than 95% copper, iron, zinc, nickel and aluminium. Au and Ag were not extracted in this solution, however, more than 95% of Au and 100% of Ag were selectively leached with a mixed solvent (0.2M ammonium thiosulfate, 0.02M copper sulfate, 0.4M ammonium hydroxide). Finally, the residues were reacted with a NaCl solution to leach out Pb while sulfuric acid was used to leach out Sn. Recoveries reached 95% and 98% in solution, respectively.

• Journal of Electrochemical Science and Technology
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• v.9 no.2
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• pp.157-162
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• 2018

In the study, herbaceous biomass waste including giant miscanthus, corn stalk, and wheat stalk were used to prepare commercially valuable activated carbons by KOH activation. The waste biomass predominantly consists of cellulose/hemicellulose and lignin, in which decomposition after carbonization and activation contributed to commercially valuable specific surface areas (>$2000m^2/g$) and specific capacitances (>120 F/g) that exceeded those of commercial activated carbon. The significant electrochemical performance of the herbaceous biomass-derived activated carbons indicated the feasibility of utilizing waste biomass to fabricate energy storage materials. Furthermore, with respect to both economic and environmental perspectives, it is advantageous to obtain activated carbon from herbaceous biomass waste given the ease of handling biomass and the low production cost of activated carbon.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.253-256
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• 2006

This paper shows the study on application of the law temperature energy in the deep seawater. Deep, cold seawater has long been recognized as a valuable ocean energy resource. Recently, research and experimentation has been conducted on energy systems using deep seawater: deep seawater air conditioning system, ice-making device, salt and fresh-water manufacturing system and the Spray freeze drying system for extracting valuable material of the deep seawater. They are technically and economically feasible today: once installed, the energy is inexhaustible and there are no adverse environmental impacts. Because of the economy of scale in the air conditioning system, the seawater A/C system is most appropriate for supplying multiple buildings or hotels in a coastal area.

• Tribology and Lubricants
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• v.39 no.5
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• pp.216-219
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• 2023

This study employs molecular dynamics simulations to investigate the material behavior of workpieces in waterjet machining processes. To gain fundamental insights into waterjet machining, simulations were conducted using pure water, excluding abrasive particles. The simulation model comprised thousands of water molecules interacting with a single crystal metal workpiece. Water molecule clusters were imparted with various velocities to initiate collisions with the metal workpiece. The material behavior of the metal surface was analyzed with respect to the applied velocity conditions, considering the intricate interplay between water molecules and the workpiece at the atomic scale. The results demonstrated that the machining of the metal workpiece occurred only when water molecules were endowed with velocities above a certain threshold. In cases where energy was insufficient, the metal workpiece exhibited a slight increase in surface roughness due to mild plastic deformation, without undergoing substantial material removal. When machining occurred, the ejection of material revealed a 3-fold symmetric pattern, confirming that material removal in waterjet machining of the metal workpiece is primarily driven by plastic deformation-induced material ejection. This research provides crucial insights into the mechanisms underlying waterjet machining and enhances our understanding of material behavior during the process. The findings can be valuable in optimizing waterjet machining techniques.

• 보존과학연구
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• s.30
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• pp.63-77
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• 2009

Scientific studies of conservation techniques and materials in Korea have experienced fast development since international practice and academic knowledge have been introduced to Korea from Japan, France, Germany, and etc from the late 1960s. In recent years, it has been observed that the academic standard of research and the level knowledge of the field in Korea at present are far advanced to compete with many countries. However, many Korean cases still have displayed that the standard and the quality of conservation practice need to be improved. This research examined several cases of derelict restoration of metal relics executed by non-conservators and the effects of their ignorant use of irreversible materials on the valuable objects. The purpose of the study is to display the problem of such treatments and to suggest a need of framework to prevent the loss of original form from them. Metal Buddha statue (Cosmic Buddha) in Borim Temple (National Treasure No. 117), which was conserved by an unexperienced non-conservator, has suffered from a serious problem of corrosion because of the use of destructive material, iron chloride. Another case for metal Buddha statue in Dopian Temple (National Treasure No. 63) displays a representative example of using irreversible materials, Cashew and such ignorant application made a later conservation treatment so difficult in removing the material from the surface of the statue. In conclusion, the research argued that the understanding of materials used in the objects, and the value of relics is important, and pre-experiments before applying conservation materials to a valuable heritage are essential in the conservation treatment.

• Resources Recycling
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• v.19 no.1
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• pp.57-65
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• 2010

Recently, we have investigated the recovery of resources from the waste material of manufacturing printed circuit board. As printed circuit board or chip has become light, small, high reliability, it is necessary to reuse and recover resources from them. Especially, the printed circuit board that has been used for important mobile electronic pans are plated with min.0.03 ${\mu}m$ to max.50 ${\mu}m$. As increasing the cost of gold, raw material, chemicals, payments and waste material, it has been accelerated the competition for reuse and recovery. But, it is insufficiency of technician and equipments for the recovery of effective resource. In this paper, as analyzing the technical trend of gold recovery and waste back board from the manufacturing process of printed circuit board, it may be effective of recycling, further more it may be contributed to develop the valuable resources.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.4
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• pp.326-331
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• 2023

The utilization of scanning transmission electron microscopy (STEM) in conjunction with cathodoluminescence (CL) has emerged as a valuable tool for the investigation of material optical properties. In recent years, this technique has facilitated significant advancements in the fields of plasmonics and quantum emitters by surpassing prior technical restrictions. The review commences by providing an outline of the diverse STEM-CL operating modes and technical aspects of the instrumentation. The review explains the fundamental physics of light production under electron beam irradiation and the physical basis for interpreting STEM-CL experiments for different types of excitations. Additionally, the review compares STEM-CL to other related techniques such as scanning electron microscope CL, photoluminescence, and electron energy-loss spectroscopy.

• Geomechanics and Engineering
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• v.9 no.4
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• pp.447-464
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• 2015

Millions of scrap tires are discarded annually in Turkey. The bulk of which are currently landfilled or stockpiled. These tires consume valuable landfill space or if improperly disposed, create a fire hazard and provide a prolific breeding ground for rats and mosquitoes. Used tires pose both a serious public and environmental health problem which means that economically feasible alternatives for scrap tire disposal must be found. Some of the current uses of scrap tires are tire-derived fuel, creating barrier reefs and as an asphalt additive in the form of crumb rubber. However, there is a much need for the development of additional uses for scrap tires. One development the creation of shreds from scrap tires that are coarse grained, free draining and have a low compacted density thus offering significant advantages for use as lightweight subgrade fill and backfill material. This paper reports a comprehensive laboratory study that was performed to evaluate the use of a shredded tire-sand mixture as a backfill material in trench conditions. A steel frame test tank with glass walls was created to replicate a classical trench section in field conditions. The results of the test demonstrated that shredded tires mixed with sand have a definite potential to be effectively used as backfill material for buried pipe installations.

• School Mathematics
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• v.4 no.3
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• pp.331-346
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• 2002

This study has two purposes. One is to know that it is Possible to use portfolio in the elementary math class. The other is to make a useful method for using portfolio. We got the following conclusion through the study. Portfolio gave students an opportunity that they could review their mathematical thinking. But it couldn't work very well for the low-level students. They didn't pay attention to the class. So, careful prepa-ration and training were necessary for the portfolio material. And the portfolio material must be prepared by appropriate contents. Teacher had to do math class by considering students ability. The math class could be much better for motivation, teaching-learning activity impro-vement and communication tool by using portfolio material. There are several imple-mentation processes in preparation, execution and utilization of the class. 1) Preparation: Teacher must decide if it is appropriate for portfolio by analyzing the course and textbook and set a final goal. And then teacher has to select an appropriate item and make a schedule for the class. The portfolio material must contain valuable things from which students learn mathematics and use in their life. The student level, utilization purpose and contents are considered when one prepares portfolio material. 2) Execution: Students are supposed to understand about the portfolio very well. It is important for them to get the opportunity for reviewing through math class diary, their opinion, friends opinion and teachers opinion. 3) Utilization: Parents review ameliorates the communication among teacher, student and parents about learning activity.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.3
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• pp.243-251
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• 2018

In the shipyard, a lot of data is generated, stored, and managed during design, construction, and operation phases to build ships and offshore structures. However, it is difficult to handle such big data efficiently using existing data-handling technologies. As the big data technology is developed, the ship and offshore industries start to focus on the existing big data to find valuable information from it. In this paper, the material requirement estimation method of offshore structure piping materials using big data analysis is proposed. A big data platform for the data analysis in the shipyard is introduced and it is applied to the analysis of material requirement estimation to solve the problems in piping design by a designer. The regression model is developed from the big data of piping materials and verified using the existing data. This analysis can help a piping designer to estimate the exact amount of material requirement and schedule the purchase time.