• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.29 no.3
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• pp.51-59
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• 1997

Dissolving pulp is a low yield(30∼35%) bleached chemical pulp that has a high cellulose content (95% or higher) suitable for use in cellulose derivatives such as rayon, cellulose acetate. This research was studied for dissolving pulp preparation as the raw material of viscose rayon from commertial pulps. (TMP, CP, DIP) In the change of pulp(cellulose) characteristics after sodium hypochlorite and solvolysis treatment. the following results were obtained In the case of sodium hypochlorite pretreatment, we have obtained pulp that high purity cellulose, but degree of polymerization was inclined to decrease less than 170∼240. Comparing sodium hypochlorite pretreatment and solvolysis pretreatment, solvolysis pretreatment is superior to sodium hypochlorite process for making dissolving pulp. We think that the low degree of polymerization of cellulose because of increasing degradation of cellulose during delignification treatment.

• Bulletin of the Korean Chemical Society
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• v.17 no.11
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• pp.1023-1031
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• 1996

A new synthetic route for the lanthanum β-diketonate compounds via in-situ formed lanthanum alkyl complexes was developed in the process for the development of suitable MOCVD (metal-organic chemical vapor deposition) precursors of PLT, one of the promising material for the ferroelectric film. A series of lanthanum β-diketonate compounds were successfully synthesized by this method. This new method is found to have some merits; versatile method for almost every β-diketone, β-hydroxyketone, and β-hydroxyaldehyde, short reaction time, easy purification for high purity, moderate to high yield, and easy access to anhydrous compounds. In some cases, anhydrous oligomeric products fail to show the higher volatility. On the other hand, some lanthanum β-diketonates with aromatic groups such as La(1,3-biphenyl-l,3-propandione)3 are found to have favorable properties for a precursor of lanthanum oxide, one of major components of PLT, such as low melting point, and much higher decomposition temperature. A plausible pyrolysis mechanism is proposed by the TGA, where consecutive dissociation of R, CO, CH, C, and O fragments occurs.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.6
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• pp.578-586
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• 2020

There is growing interest worldwide in a hydrogen economy that uses hydrogen as an energy medium instead of hydrocarbon-based fossil fuels as a way to combat climate change. Since hydrogen has a very low energy density per unit volume at room temperature, hydrogen must be compressed and stored in order to use as an energy carrier. There are mechanical and non-mechanical methods for compressing hydrogen. The mechanical method has disadvantages such as high energy consumption, durability problems of moving parts, hydrogen contamination by lubricants, and noise. Among the non-mechanical compression methods, electrochemical compression consumes less energy and can compress hydrogen with high purity. In this paper, research trends are reviewed, focusing on research papers on electrochemical hydrogen compression technology, and future research directions are suggested.

• Current Applied Physics
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• v.18 no.12
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• pp.1553-1557
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• 2018

Gallium nitride (GaN) nanoparticles are synthesized by the gallium particle trapping effect in a $N_2$ nonthermal plasma with metallic Ga vapor. A proposed method has an advantage of synthesized GaN nanoparticle purity because the gallium vapor from the inductively heated tungsten boat does not contain any impurity source. The synthesized particle size can be controlled by the amount of Ga vapor, which is adjusted using the plasma emission ratio of nitrogen to gallium, owing to the particle trapping effect. The synthesized nanoparticles are investigated by electron microscopy studies. High-resolution transmission electron microscopy (HRTEM) studies confirm that the synthesized GaN nanoparticles (10-40 nm) crystallize in a single-phase wurtzite structure. Room-temperature photoluminescence (PL) measurements indicate the band-edge emission of GaN at around 378 nm without yellow emission, which implies that the synthesized GaN nanoparticles have high crystallinity.

• Research in Community and Public Health Nursing
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• v.12 no.3
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• pp.755-772
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• 2001

The specific purpose of this study was as follows: 1) To identify the level of sexual awareness and demand for sex education of teenagers, their parents and teachers. 2) To investigate the attitude toward and acceptance of heterosexual friendships by teenagers, their parents and teachers. 3) To identify the experience and direction of sex education of parents and teachers. For this purpose, this study selected 341 male and female teenagers at three high schools located in a city, 119 parents with high school students and 243 elementary/middle/high school teachers. The structured questionnaire was distributed to each of them and returned by them. This study was conducted over the period between June 1. 2001 and Aug 31. 2001. A total of 720 questionnaires were distributed to them and 703 were returned. Data analysis was conducted to obtain percentage and frequency using the SAS program. As a result, the following findings were obtained: Parents and teachers showed a similar attitude about sexual awareness, but teenagers showed a different attitude. In terms of the level of feeling of and interest in 'sex', teenagers, parents and teachers were comfortable in accepting it. As for sexual curiosity in puberty, 84.8% of the parents and 95.5% of the teachers responded that it was natural, whereas only 14.7% of teenagers responded that it was natural. But As for the item that 'sex is natural as one of human needs', 3.6% of the teenagers, 16.8% of the parents and only 1.2% of the teachers responded that it was not. As for the item that 'A man has a stronger sexual impulse than a woman', 6.1% of the teenagers, 16.8% of the parents and 17.3% of the teachers responded that it was not. 64.2% of the teenagers and 90.2% of the teachers responded that it was impossible to overcome the sexual impulse, whereas only 8.4% of the parents responded that it was possible. As for the item of masturbation, 64.5% of the teenagers responded that it was possible for male students and not possible for female students. 67.2% of the parents and 91.1% of the teachers responded that it was possible regardless of sex. As for the item of an attitude toward virginal purity, both the parents and teachers showed that virginal purity was important for both man and woman, but teenagers showed a weak awareness of virginal purity. As for the item, 'It is possible to have sexual intercourse with a lover during adolescence', 20.2% of the teenagers, 79% of the parents and 87.7% of the teachers responded that it was impossible. As for the item 'It is necessary to keep premarital virginal purity for a happy married life', 21.1% of the teenagers, 74.8% of the parents and 55.1% of the teachers responded that it was necessary, which shows that teenagers had a different opinion than parents and teachers. In case of pregnancy in adolescence, most of the responding teenagers, parents and teachers chose abortion. As for the item 'female refusal on male sexual approach', respondents accepted female refusal as they did for orders of teachers, parents and adolescents. As for item 'An assaulter is entirely to blame for sexual assault', all of three groups responded in the affirmative.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.239-239
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• 2003

As a result of the recent miniaturization and enhancement in the performance of thin film inductors and thin film transformers, there are increased demands for the thin films with a high magnetic permeability in the high frequency range, a high saturation magnetization, a high electrical resistivity, and a low coercive force. In order to improve high frequency properties, we will investigate anisotropy field by shape and size of pattern. The Fe-Al-O thin films of 16mm diameter and 1$\mu\textrm{m}$ thickness were deposited on Si wafer, using RE magnetron reactive sputtering technique with the mixture of argon and oxygen gases. The fabricating conditions are obtained in the working partial pressure of 2m Torr, O$_2$ partial Pressure of 5%, Input power of 400w, and Al pellets on an Fe disk with purity of 99.9%. For continuous thin film is the 4Ms of 19.4kG, H$\sub$c/ of 0.6Oe, H$\sub$k/ of 6.0Oe and effective permeability of 2500 up to 100MHz. In this work, we expect to enhanced effect of magnetic anisotropy on patterned of Fe-Al-O thin films.

• Korean Journal of Materials Research
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• v.27 no.10
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• pp.552-556
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• 2017

Evaluation of the durability and stability of materials used in power plants is of great importance because parts or components for turbines, heat exchangers and compressors are often exposed to extreme environments such as high temperature and pressure. In this work, high-temperature corrosion behavior of 316 L stainless steel in a carbon dioxide environment was studied to examine the applicability of a material for a supercritical carbon dioxide Brayton cycle as the next generation power plant system. The specimens were exposed in a high-purity carbon dioxide environment at temperatures ranging from 500 to $800^{\circ}C$ during 1000 hours. The features of the corroded products were examined by optical microscope and scanning electron microscope, and the chemical compound was determined by x-ray photoelectron spectroscopy. The results show that while the 316 L stainless steel had good corrosion resistance in the range of $500-700^{\circ}C$ in the carbon dioxide environment, the corrosion resistance at $800^{\circ}C$ was very poor due to chipping the corroded products off, which resulted in a considerable loss in weight.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.12
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• pp.591-596
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• 2006

we have been developed on the ultra high concentration ozone generator system which is the core technology in the realization of the semiconductor photoresist strip process using the ozone-vapor chemistry. The proposed ozone generator system has the structure of the surface discharge type which adopt the high purity ceramic dielectric tube. We investigate the performance of the proposed ozone generator system experimentally and the results show that the system has very high ozone concentration characteristics of $19.7[wt%/O_2]$ at the flow rate of $0.3[{\ell}/min]$ of each discharge cell. As a result of the silicon wafer photoresist strip test, we obtained the strip rate of about 400[nm/min] at the ozone concentration of $16[wt%/O_2]$ and flow rate of $8[{\ell}/min]$. So, we confirmed that it's possible to use the proposed high concentration ozone generator system for the ozone-vapor photoresist strip process in the semiconductor and FPD industry.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.3
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• pp.77-80
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• 2003

An innovative ozonizer has been developed using a high frequency, surface discharge and a high purity Ti-Si-AI ceramic catalyst as a dielectric component. Using a type of thin film, a thin cylindrical compound ceramic catalyst layer was adhered to the outside surface of its inner electrode. An alternating current (AC) exciting voltage with frequencies from 0.6 KHz to 1.0 KHz and peak-to-peak voltages of 4-6 ㎸ was applied between the electrodes to produce a stable high-frequency silent discharge. A substantial reduction of the exciting voltage was also enabled by means of a thin Ti-Si-Al ceramic catalyst tube. As a result, the ozonizer can effortlessly obtain the required ozone concentration (50-60 g/$m^2$ for oxygen) and high ozone efficiency consumption power (180 g/kWh for oxygen) with-out the assistance of any particular methods. For purposes of this experiment, oxygen gas temperature was set at 2$0^{\circ}C$, with an inner reactor pressure of 1.6 atm at 600 Hz and a flow rate of 2 l/min.

• Nuclear Engineering and Technology
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• v.56 no.4
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• pp.1339-1346
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• 2024

Electrorefining in molten salts is used for purifying actinides. Optimizing electrorefining is key to minimizing processing time and radiological waste. One possible way of improving electrorefining efficiency is using an AC superimposed DC waveform. This waveform has demonstrated potential benefits in aqueous solutions but has never been utilized in a molten metal, molten salt application. This work investigates the effects of using an AC superimposed DC waveform on molten bismuth electrorefining in a molten LiCl-KCl-CaCl2 eutectic. Bismuth has been identified as a potential surrogate for plutonium electrorefining and a potential cathode in electrorefining used nuclear fuel (UNF). All electrorefining runs resulted in a high purity cathode ring and high yield with exception of the run using a low-frequency, high-amplitude superimposed AC waveform, which experienced some contamination and a lower yield. The other three AC superimposed DC runs experienced an average yield 6.7 % higher than the average yield of the DC runs. The electrorefining run using the high-frequency, high-amplitude superimposed AC signal had the highest yield. It is recommended in future studies to investigate the statistical variability of electrorefining yield and current efficiency and the impact of AC superimposed DC waveforms on solidified bismuth anodes.