• Journal of the Korean Wood Science and Technology
• /
• v.13 no.3
• /
• pp.49-53
• /
• 1985

The effects of pre-treatments, the hot water extraction of wood meal and the addition of chemical ($CaCl_2$) to wood-cement water system on the properties of wood-cement composite such as modulus of rupture (MOR), modulus of elasticity (MOE), water sorption ratio and swelling ratio of resulting boards were studied in this experiment. The wood meals through 0.83mm(20 mesh) and retained on 0.42mm(35 mesh) screen were prepared from Pinus densiflora S. at Z. and Larix leptolepsis G. For hot water extraction, 500 grams of wood meal for each species were heated to boiling with 1,500ml of distilled water in 2-liter beaker for 6 hours. Every 2 hours, the wood meals were washed with boiling distil1ed water and reheated to boiling again. After 6 hours boiling, the boiled wood particles were collected by pouring this particles on 200 mesh screen. The collected particles then washed twice with hot distilled water and dried for 24 hours in an oven at $109{\pm}20^{\circ}C$. A mixture of 663.4 grams of cement with 331.7 grams of wood meal based on oven-dry weight were dry-mixed in a plastic vessel. The mixture was kneaded with 497.6ml of distilled water in the ratio of 1.5ml of water to a gram of wood meal. To add calcium chloride to the mixture as an accelerator, $CaCl_2$ 4% solution by weight per volume, was added to pine-or larch-cement board in the ratio of 3% to cement weight. To set wood-cement board, this mixture was clamped at 30cm ${\times}$ 30cm, in thickness of 1.5cm for 3 days at room temperature, declamped and then placed at open condition for 17 days. The target density was 1.0. The four specimens sized to 5cm in width and 28cm in length were used for MOR and MOE test for each treatment. After MOR test, the tested specimens were cut to the size of 5cm ${\times}$ 5cm for water sorption and swelling test. The twenty specimens used to measure the water sorption ratio (soaking 24 hours) and ten of these were used for swelling ratio measurement The results obtained were as follows: 1) Larch was not suitable for wood-cement boards because larch-cement board developed no strength, but pine showed 97.9kg/$cm^2$ by hot water extraction. 2) To increase MOR, hot water extraction was more effective than the addition of $CaCl_2$ in pine and larch because the $CaCl_2$ addition was seemed to speed up the ratio of cement hydration without reacting with the wood substances. 3) The water sorption ratio was lowered by the addition of $CaCl_2$ to wood-cement system because the chemical additive accelerated the rate of cement hydration. 4) In pine-cement board, the swelling ratio from 0.37 to 0.42 percent was observed in length and the swelling ratio from 0.88 to 2.0 percent in thickness. As a rule, the swelling ratio of wood-cement board was very low and the swelling ratio in thickness was higher than in length.

• Journal of the Korean GEO-environmental Society
• /
• v.3 no.2
• /
• pp.23-33
• /
• 2002

Examined a practical use possibility of paper fly ash that is industrial by-product as a stabilization/hardening agent. Performed unconfined compression test, scanning electron microscopy and pH analysis etc. for 100% paper fly ash-soil mixtures and each paper fly ash-soil mixtures that add cement as the second addition and sulfate component of small quantity for strength promotion and so on. In all cases, strength of admixtures increased according as curing time and mixing ratio increases but almost strength is revealed at mixing early and expressed maximum strength increase efficiency at mixing ratio 9% with raw soil. Compare with the case that use paper fly ash only, in case of cement amount 10~30% was included in paper fly ash, strength of admixtures increases two times and 40% was included, that increases from five to eight times.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.12 no.2
• /
• pp.228-235
• /
• 2009

We synthesized glycidyl azide monomer(GAM) as a monomer for polymerization of glycidy azide polymer(GAP) which is a promising energetic prepolymer for a plastic-bonded explosive. Using quantitative real-tim in-situ infrared(in-situ IR) spectroscopy, kinetic study on the cationic ring opening polymerization of GAM was carried out. The reaction rate was obtained from monitoring the change of ether C-O stretching band($1050cm^{-1}$) in series IR spectra. The reaction was in accordance with the first-order reaction law for each of reaction temperature at 100/1 mole ratio of [GAM]/[$BF_3*etherate$]. In the ring opening polymerization of GAM, with ratio of [GAM]/[$BF_3*etherate$] to equal 100/1 at various temperature, the activation parameters obtained from the evaluation of kinetic data were ${\Delta}H^*$=14.34kcal/mol, ${\Delta}S^*=-12.31cal/mol{\cdot}K$ and $E_a$=14.89kcal/mol.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.2
• /
• pp.18-26
• /
• 2009

When channel state information (CSI) is available at the transmitter, the system throughput can be enhanced by adaptive transmissions and opportunistic multiuser scheduling. In this paper, we consider multiple-input multiple-output (MIMO) systems employing bit-interleaved coded orthogonal frequency division multiplexing (BIC-OFDM). We first propose a bit-loading algorithm based on the Levin-Campello algorithm for the BIC-OFDM. Then we will apply this algorithm to the MIMO system with a finite set of constellations, by reassigning residual power on each stream Simulation results show that proposed bit-loading scheme which takes the residual power into account improves the system performance especially at high signal-to-noise ratio (SNR) range.

• Journal of Conservation Science
• /
• v.31 no.4
• /
• pp.477-488
• /
• 2015

At this, in this study, some tests were conducted to come up with a method to minimize intervention, to reduce the secondary damage to original materials, and to produce remarkable reinforcing effects. The followings show objective standards. The proportion of original material to steel reinforcement bar (the ratio of steel reinforcement bar) needs to be calculated in light of weathering intensity. Second, in the case of partial damage, prosthetic treatment is applied to add new stone materials to original materials. In that case, the ratio of steel reinforcement bar should be calculated based on material that is highly resistant to weathering. With the results of this study, it is possible to suggest conditions that can structurally stabilize stone cultural heritage, according to the weathering area. As a result, the ratio of steel reinforcement bars can be 0.13 to 0.23 in the case of $800kgf/cm^2$ or less, 0.24 to 0.28 in $800kgf/cm^2$ or higher, and 0.29 to 0.5 in $1200kgf/cm^2$ or higher. In particular, there is the need to take the coefficient of rupture of stone material and the properties of the steel reinforcement bar into account in cases of calculating the ratio of steel reinforcement bars according to weathering intensity.

• Proceedings of the IEEK Conference
• /
• 2000.06b
• /
• pp.48-51
• /
• 2000

We proposed the new driving waveform which has changed the waveform of sustain division to improve luminous efficiency in plasma display panel. This sustain waveform is to add the ramp to the rectangular waveform, resulting in self-erasing discharge in the falling edge region. The proposed waveform has improved the luminous efficiency of 30％ even in low driving frequency(25kHz), whereas the conventional driving waveform using the self-erasing discharge can improve the luminous efficiency only in high driving frequency( >150kHz). Front the results of this paper, we hope that the variety study on frequency and duty ratio, ramp waveform will increase the luminous efficiency.

• The Korean Journal of Food And Nutrition
• /
• v.23 no.4
• /
• pp.446-452
• /
• 2010

In this study, Boehmeria nivea were extracted with water and ethanol, and antioxidative activity was investigated along with the quality of cookies prepared with added Boehmeria nivea, as a functional food. Among the water and ethanol extracts, high electron donating abilities were found. we selected various quantities of Boehmeria nivea(0%, 3%, 6%, 9%, 12%, 15%) to add to the cookies as an independent variable and performed sensory tests, as well as, measured chromaticity, and property of matter measurements. The rates of brightness, redness, and yellowness(p<0.001) changed significantly with increasing quantities Boehmeria nivea. The rates for spread ratio, hardness, brittleness, and chewiness(p<0.001) also changed siginificantly with increasing amounts Boehmeria nivea. Finally, texture(p<0.05), appearness, sweetness(p<0.01), bitterness, and overall quality(p<0.001) were examined in sensory tests and showed significant differences. Based on the above results, the cookies that contained 3~9% of Boehmeria nivea presented the best quality.

• Journal of Sericultural and Entomological Science
• /
• v.19 no.1
• /
• pp.9-13
• /
• 1977

This experiment was carried out to know relationship between economical characters and kinds of extracted cellulose powders, extracting methods and cellulose composition. The results obtained are summarized as follows; 1. Among the matters for cellulose resources, mulberry branch is the most useful in economical characters such as larval weight, ratio of cocoon shell and mortality, followed by pine branch. 2. Though both PA-method and NaOH-treatment are equally effective in the larval growth, the latter may be more recommendable because of its economical convenience. 3, It may be desirable to add 15 to 22.5 per cent of cellulose powder per dry matter in the diet composition

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.77.1-77.1
• /
• 2016

We investigate the properties and detection conditions for the planetary caustic perturbation of close-separation planets. To find the properties of the planetary caustic perturbation, we construct deviation maps by subtracting the single-lensing magnification of the lens star from the planetary lensing magnification for various lensing parameters. We find that each deviation area of the positive and negative perturbations disappears at the same normalized source radius according to a given deviation threshold regardless of mass ratio but disappears at a different normalized source radius according to the separation. We also estimate the upper limit of the normalized source radius to detect the planetary caustic perturbation. We find simple relations between the upper limit of the normalized source radius and the lensing parameters. From the relations, we obtain an analytic condition for the detection limit of the planet, and which show that we can sufficiently discover a planet with the mass of sub-Earth for typical microlensing events. Therefore, we expect to add the number of low-mass planets in the next-generation microlensing experiments and conclude that our detection condition of the planet can be used as a important criteria for maximal planet detections considering the source type and the photometric accuracy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.87-88
• /
• 2006

It is needed several large reservoirs and long time in order to remove suspended solid like steel fines and iron oxide at steel making factory. If removing rate of suspended solid in rolling coolant is improved, the productivity of working process can be increased and the area of reservoir can be reduced. Pre-treatment to add extra magnetization of suspended solid was studied Iron hydroxide and electrolytic dissociation were used for pretreatment. High gradient magnetic separation (HGMS) system was used for removing of magnetized suspended solid. Removing ratio showed over than 99% in the coolant containing magnetic fines. Magnetic properties of suspended solid were investigated after mixed with Al2(SO2)3 and organic flocculant by using electrochemical treatment.