• Journal of Korean Society of Environmental Engineers
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• v.29 no.9
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• pp.1013-1019
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• 2007

Electronic wastes have increased tremendously. However, any reliable treatment methodologies have rarely been established. Electronic wastes have posed serious disposal problem due to their physico-chemical stability. This paper investigated the application possibility of pyrolysis for the purpose of recycling the p-CCL(phenol based Copper Clad Laminate). Thermogravimetric analysis(TGA) was used to investigate the thermal decomposition pattern of p-CCL. We elucidated the characteristics of pyrolysis by-products at operating temperatures of 280, 350 and $600^{\circ}C$. GC/MS and FT-IR were used to characterize the liquid by-products along with general characterization methods such as Ultimate Analysis, Proximate Analysis and Heating Value, whereas general characterization methods were only introduced for the solid by-products. At a heating rate of $5^{\circ}C$/min, TGA curves exhibited three decomposition stages: (1) low-temperature decomposition region$(<280^{\circ}C)$, (2) medium temperature region$(280\sim350^{\circ}C)$ and (3) high-temperature region$(>350^{\circ}C)$. The major compounds of liquid by-products at low- and medium-temperatures were accounted for by water and phenol, whereas branched phenols and furans were major compounds at high-temperatures. As the temperature increases, volatile quantities decreased but the fixed carbon increased. High heating values of solid by-products($7,400\sim7,600$ kcal/kg) would suggest that the solid by-products could be applicable as fuel. In addition, high fixed carbon but low ash content of the solid by-products offered an implication that they are capable of being upgradable for adsorbent after applying appropriate activating process.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.3-10
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• 2017

Counting Bloom filters (CBFs) have been popularly used in many network algorithms and applications for the membership queries of dynamic sets, since CBFs can provide delete operations, which are not provided in a standard 1-bit vector Bloom filter. However, because of the counting functions, a CBF can have overflows and accordingly false negatives. CBFs composed of 4-bit counters are generally used, but the 4-bit CBF wastes memory spaces by allocating 4 bits for every counter. In this paper, we propose a simple alternative of a 4-bit CBF named ternary Bloom filter (TBF). In the proposed TBF structure, if two or more elements are mapped to a counter in programming, the counters are not used for insertion or deletion operations any more. When the TBF consumes the same amount of memory space as a 4-bit CBF, it is shown through simulation that the TBF provides a better false positive rate than the CBF as well as the TBF does not generate false negatives.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.6
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• pp.589-595
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• 2013

Solution processed conjugated molecules enable to manufacture various electronic devices by unconventional and cost effective patterning methods as screen or gravure printing. Spin-coating is the most popularly used method to form conjugated polymeric film for various electronic devices. The coating method has certain disadvantages such as a large amount of unwanted wastes, difficulty forming a film with a large area, and impossible to apply roll-to-roll manufacturing. We present here a promising alternative coating method, bar-coating for conjugated polymer film and OLED with the bar coated light emitting layer. In this papers, we show atomic force microscope images of spin- and bar-coated Poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT) films on substrate. The bar-coated film showed a slight lower RMS roughness (1.058 [nm]) than spin-coated film (1.767 [nm]). It means the bar-coating is suitable method to form light emitting layers in OLEDs. By using bar-coating process, an OLED obtained with 4.7 [cd/A] in maximum current efficiency.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.104-113
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• 2014

The existing rough mode decision (RMD) algorithm, used in HEVC standard loses the coding efficiency and wastes encoding time when encoding using transform skip mode (TSM) because the RMD algorithm in HEVC uses a selection method that is designed for DCT, not for TSM. This paper proposes a new RMD algorithm for TSM in HEVC. Our proposed RMD algorithm enhances the coding efficiency by employing a new cost function to increase the probability of selecting the best intra prediction mode for TSM. In addition, it reduces the encoding time by skipping the encoding process of least feasible TSM based on a newly proposed threshold value. The experiment results show that the proposed method achieves coding gains of -0.3% for screen contents with a 10% reduction in encoding time compared to those of the HEVC standard.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.10
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• pp.1093-1100
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• 2015

Since the security of RSA cryptosystem depends on the difficulty of factoring integers, it is the most important problem to factor large integers in RSA cryptosystem. The Lenstra elliptic curve factorization method(ECM) is considered a special purpose factoring algorithm as it is still the best algorithm for divisors not greatly exceeding 20 to 25 digits(64 to 83 bits or so). ECM, however, wastes most time to calculate $M{\cdot}P$ mod N and so Montgomery and Koyama both give fast methods for implementing $M{\cdot}P$ mod N. We, in this paper, further analyze Montgomery and Koyama's methods and propose an efficient algorithm which choose the optimal parameters and reduces the number of multiplications of Montgomery and Koyama's methods. Consequently, the run time of our algorithm is reduced by 20% or so than that of Montgomery and Koyama's methods.

• Resources Recycling
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• v.22 no.2
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• pp.71-77
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• 2013

Electronic products such as appliances, computers, and cellular phones have printed circuit boards (PCBs) in common and the PCBs in the waste electronic products contain valuable metals and organic resins. In Korea, recovery and recycling of the organic resins as well as the valuable metallics from the wastes are required indeed as the most of resources are being imported from abroad. In this article, the patents and papers for the recycling of organic residues from the waste PCBs were collected and analyzed. The open patents of USA (US), European Union (EP), Japan (JP), and Korea (KR) and SCI journals from 1979 to 2012 were investigated. The patents and journals were collected using key-words and filtered by the definition of the technology. The patents and journals were analyzed by the years, countries, companies, and technologies and the technical trends were discussed in this paper. It is showed sluggish relatively activity of published papers and patent applications for polymer manufacturing technology in local and abroad.

• Journal of Korea Society of Waste Management
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• v.35 no.8
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• pp.692-700
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• 2018

In this study, the results of PBDEs and HBCDs of the products and waste that contain BFRs such as domestic electronic products, automobiles and textile products were compared with international management standards, and their excess rates were calculated. Deca-BDE was detected among the PBDEs in TV rear cover plastics, car seats, automotive interior plastics, and automobile shredding residues of products and waste containing BFRs. The comparison with Basel Convention management standards (1,000 mg/kg) for PBDE-containing wastes (4 types in total) shows that the excess rate of all samples was less than 1.5%. The estimated excess rate compared to the EU and Basel convention management standards (1,000 mg/kg) for PBDEs (4 species + deca-BDE) and TV rear cover plastics was 37.5% (30 of 80 samples exceeded the standards). The estimated excess rate compared to the Basel convention management standards (1,000 mg/kg) for HBCD, building materials products and waste was 15.7% (17 of 108 samples exceeded the standards). In the case of PBDEs, it is necessary to remove only the rear cover of CRT TV among the electric and electronic products and treat it in the flame retardant treatment facility to improve the recycling collection system. In the case of HBCD, it is necessary to appropriately dispose of the recycled materials, heat insulation materials, TV plastics, and styrofoam in marine fishery among construction materials and restrict the use as recycled raw materials.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.1
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• pp.219-230
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• 2023

Marine waste is classified according to its location into coastal waste, floating waste, and submerged waste. As awareness of environmental issues increases, research on marine submerged waste in addition to visible trash is needed. In Korea, which is surrounded by the sea on three sides, this is a study on the distribution of marine sedimentary waste by type in the West Sea of Korea. Through the study, waste synthetic resin, scrap metal, waste tires, and others appeared in the order of large amounts. As a result showing the seriousness of waste synthetic resin among sediments deposited in the West Sea, it is expected to have a huge impact not only on the marine ecosystem but also on our lives in the near future. Through this study, it is judged that it will be helpful for future collection activities by recognizing marine submerged waste that was not known because it was invisible.

• Resources Recycling
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• v.17 no.2
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• pp.3-15
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• 2008

Different toxic wastes are disposed of in our surroundings and these will ultimately threaten the existence of living organisms. Biohydrometallurgy, which includes the processes of bioleaching and bioremediation through the activities of microorganisms such as bacterial or fungal species, is a technology that has the potential to overcome many environmental problems at a reasonable economic cost. Bioleaching were carried out for dissolution of metals from different materials using most important metal mobilizing bacteria such as Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Laptospirillum ferrooxidans. According to the reaction, bioleaching is parted as direct and indirect mechanism. In direct mechanism the bacteria oxidize the sulphides minerals by accepting electron and producing sulphuric acid in leaching media for their growth and metabolism. In other hand the indirect bioleaching is demonstrated as the oxidation of sulphides mineral by the oxidant like $Fe^{3+}$ produced by the iron oxidizing bacteria. Through this process, substantial amount of metal can be recovered from low-grade ores, concentrates, industrial wastes like sludge, tailings, fly ash, slag, electronic scrap, spent batteries and spent catalysts. This may be alternative technology to solve the high deposition of waste, which moves toward a healthy environment and green world.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.567-573
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• 2012

Compared with the natural marble, the artificial marble has the advantages of excellent appearance, high degree of finish, even color, fine pressure and wear resistance, bear erosion and weathering, etc. It can be widely used in kitchen countertops, bath vanity tops, table tops, furniture, reception desks, etc. However, large amounts of artificial marble waste such as scraps or dust have been generated from sawing and polishing processes in artificial marble industry. Waste from artificial marble industry is increasing according to demand magnification of luxurious interior material. Artificial marble wastes can be recycled as aluminum oxide used as raw materials in electronic materials, ceramics production, etc., and methyl methacrylate(MMA) which become a raw material of artificial marble by pulverization, pyrolysis and distillation processes. The characteristics of artificial marble wastes was analyzed by using TGA/DSC and element analysis. Crude aluminum oxide was obtained from artificial marble waste by pulverization and thermal decomposition under nitrogen atmosphere. In this work, Box-Behnken design was used to optimize the pyrolysis process. The characteristics of crude aluminum oxide was evaluated by chromaticity analysis, element analysis, and surface area.