• Journal of the Korea Institute of Building Construction
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• v.5 no.4 s.18
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• pp.115-120
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• 2005

In recent years, polymer-modified mortars using polymer dispersions have been widely used as finish and repair materials in the construction industry because of their excellent properties compares to those of ordinary cement mortar. Especially, the adhesion improvement of ordinary cement mortar and concrete has attracted a great deal of attention from researchers, and several unique and simply applicable techniques for the adhesion improvement have been developed. The purpose of this study is to evaluate the abrasion resistance of polymer-modified mortar according various curing methods. The polymer-modified mortar are prepared with various polymer-cement ratios, and are subjected to three curing methods such as dry rure, standard cure and freezing and thawing cure after two curing methods, and then tested for abrasion. From the test results, the polymer-modified mortars with various polymer-cement ratios have some superior abrasion resistance compared with plain mortar. The abrasion resistance of polymer-modified mortars increase with an increase in the polymer-cement ratio, and is better under water cure than any other curing methods. It is concluded that the abrasion resistance of cement mortar is markedly improved by modifying of polymer dispersion.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1240-1249
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• 2008

Jacket anchor was developed to increase the pullout resistance of general ground anchor in soft ground, and the mechanism of pullout resistance of jacket anchor was analyzed. Also, the ultimate bond stress of jacket anchor was estimated by ultimate resistance which is determined by field tests. Grout milk was injected into the jacket to make grout bulb of jacket anchor. The formation of grout bulb of jacket anchor increases the diameter of grout bulb, ground strength and confining pressure between anchor grout and soil. From the twelve field test results, it was observed that the pullout resistance of jacket anchor is 15.38~295.02%(average 83.53%) greater than that of general ground anchor, and plastic deformation of jacket anchor is 20.78~1,496.45%(average 288.78%) smaller than that of general ground anchor at the same load cycle. Especially, it was investigated that the increase of ultimate resistance over 200% and the reduction of plastic deformation over 600% was obtained in gravel layer. It means that the jacket anchor is superior to the general ground anchor in gravel layer. Finally, the ultimate bond stress was proposed to design jacket anchor.

• The Korean Journal of Zoology
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• v.3 no.1
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• pp.9-12
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• 1960

The present status of insecticide resistance of Korean mosquitoes is still unknown. The experiment cited below is a part of our series of resistance tests on Korean mosquitoes. The test was carried out during the summer of 1959 to ascertain the degree of resistance of Culex pipiens to insecticides currently used. Culex pipiens eggs were collected from ditches in Seoul City and reared in laboratory with media consisted of the following : Distrilled water 1.0 liter, Magnesium sulfate (MgSO$_4$.7$H_2O$) 1.0gram , Calcium sulfate (CasO$_4$.2$H_2O$) 0.5gram ; Sodium cholride 0.5 gram. A Sufficient amount of beer yeast was also used as a larvar food. Late third and early fourth instar larvae were selected for testing. The results are summarized in the following. THe LC-50 of Culex pipiens to insecticides were 0.061 ppm in p, p-DDT , 0.045 ppm in ${\gamma}$-BHC and0.029 ppm in malathion. Comparing these with LC-50 doses of Orlando laboratory strain, it can be pointed out that the present resistance of Seoul strain shows about a ten-fold increase in DDt, and a fourfold increase in ${\gamma}$-BHC . The resistance development of the Seoul strain has, however, not arisen so markedly as compared with data observed in other parts of Far Eastern areas received heavy insecticidal operations.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.148-149
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• 2016

In this paper, the increase in chloride resistance of footing concrete at coastal area was evaluated by replacement of Mineral Admixture. In KBC 2009, the footing concrete's minimum specific concrete strength at coastal area is determined to 35MPa. However, this is criteria only based on the strength aspect. Thus, it is not considered to increase the chloride resistance by replacement of Mineral Admixture. According to the test results of chloride ions penetration resistance, 35MPa class concrete with OPC 100% shown inaccessible state. Low-strength (24~30MPa class) concretes with Mineral Admixture, however, presented better performances. In addition, chloride diffusion coefficient tests showed identical appearance. Therefore, the current KBC's chloride resistance criteria based on only concrete strength has to review for the reason it can cause many problems (ex. cost increases by growing concrete strength and the environmental issues by a lot of cement use).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.4
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• pp.256-262
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• 1991

The corrosion effects on thermal contact resistance were experimentally studied for a given contact interface of a couple of metals. 2 cylindrically shaped test pieces, the one was carbon steel whose surface was machined by lathe and the other was stainless steel, ground, were come into contact under pressure, and then submerged to $HNO_3$ gas environment. While the corrosion process was going on, the thermal contact resistance was measured with time. The experiment was performed for 2 cases; 1) Highly compress the test pieces and then bring them to $HNO_3$ gas environment. 2) Anteriorly corrode the interface under low contact pressure and then increase the contact pressure. The results were as follows; In 1st. case of experiment, the thermal contact resistance seemed to be very stable, and showed low values with a tendancy of small decrease with time. But in 2nd. case the resistance was unstable and jumped to a value of 200-250% more then that expected for uncontaminated interface. More over it demonstrated some increase with time.

• Journal of the Korean Society of Physical Medicine
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• v.18 no.1
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• pp.51-57
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• 2023

PURPOSE: Recently, the proportion of respiratory diseases has been increasing worldwide, and deaths from respiratory diseases in Korea are increasing. Maintaining a healthy respiratory function is a crucial factor in preventing respiratory diseases. There are various ways to improve respiratory function, such as respiratory muscle and aerobic exercises. In other countries, respiratory muscle exercise is performed using a respiratory resistance mask, but such research is insufficient in Korea. Therefore, this paper proposes a respiratory exercise program using a respiratory resistance mask. METHODS: This study was conducted by dividing healthy adults in their 20s into a treadmill exercise + respiratory resistance mask group and a treadmill exercise group into an experimental group and a control group. The changes in the subject's physical function before and after exercise were confirmed by cardiopulmonary exercise and pulmonary function tests. RESULTS: As a result of the study, the experimental and control groups increased their physical function significantly (p < .05). On the other hand, when the increase rate according to the group was confirmed, the increase rate of the experimental group was higher. CONCLUSION: Based on this study, it is necessary to develop a respiratory exercise program using respiratory exercise tools such as a respiratory resistance mask and provide it easily to various subjects.

• Transactions on Electrical and Electronic Materials
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• v.10 no.2
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• pp.62-65
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• 2009

YBCO-coated conductors, called "second-generation wires," show a remarkably greater increase in the amount or speed of their resistance than BSCCO wires when a quench occurs. This is probably because of the specific resistance at their stabilizer layer, which also affects their voltage grade. YBCO coated conductors with copper as a stabilizer layer have a voltage grade of 1.5-2 V/cm, and those with stainless steel as a stabilizer layer have a voltage grade of about 0.5-0.6 V/cm. The voltage grade of YBCO coated conductors is important in selecting and applying superconducting wires to power instruments later. In this study, two kinds of YBCO-coated conductors with different stabilizer layers and one kind of BSCCO wire were prepared. Among them, based on the YBCO coated conductors that had a stainless steel stabilizer layer with a low voltage grade, five kinds of experimental samples for joining were prepared with the remaining two kinds of wires. Using the prepared samples, the current application properties and the resistance increase in the flux-flow and the quench states of the single wire and the joined wires were compared.

• Journal of the Korea Furniture Society
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• v.19 no.6
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• pp.447-451
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• 2008

This study was carried out to know the difference of vapor transmission on the thickness of Paulownia wood(Paulownia tomentosa). The behavior of moisture transmission of wood thickness direction is generally estimated by vapor permeability and vapor transmission resistance. In general, Paulownia wood is known to use of inside material for furniture making, because of the excellent ability of vapor adsorption and/or desorption. Quarter sawing Paulownia wood material is prepared and the thickness is 6.0mm, 7.0mm, 8.0mm, 9.0mm, 10.0mm, respectively. The measurement of vapor transmission were conducted by the "cup method" in accordance with JIS(Japanese Industrial Standard) Z-0208. The experiment was made in the condition of 49.8mmHg vapor pressure difference and $40^{circ}C$ at constant temperature. From the experiment results, it was considered that Paulownia wood is very stable on moisture variation and any other material conditions. In this experiment we found that the vapor permeability and vapor permeance was reduced with the increase of wood thickness to vapor direction and vapor transmission resistance and specific vapor transmission resistance was increased with the increase of wood thickness to vapor direction. Besides moisture contents of adsorption and desorption side were about 5 percent and 14 percent, respectively. Mean value was 9.5 percent and about 10 percent in dry oven method. Moisture gradient was reduced with the increase of wood thickness for a small moisture difference of adsorption and desorption side.

• Journal of the Korean Society for Precision Engineering
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• v.2 no.3
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• pp.28-40
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• 1985

In this study, to check up on the effect of the components of cutting resistance upon friction between drill and inside wall of hole in drilling, the experiment was performed with individual specimen of carbon steel, cast iron, aluminium alloy under various cutting conditions: depth of hole, cutting speed, feed rate, shape and material of specimen. On the basis of the experimental results, the following conclusions are drawn; 1. The components of cutting resis- tance were increased in proportion to the increase of depth of hole owing to frictional resistance of drill margin and chip-jamming. 2. As feed rates increase, torque and thrust were increased. When comparing to the increasing rate for these components respecitively, thrust is higher tendency than torque. 3. As drill diameter increase, torque and thrust were increased. When comparing to the increasing rate for these components respectively, torque is higher tendency than thrust. 4. In the case of torque, the frictional resistance between drill margin and inside wall of drilled hole accounts for about 20 percent of carbon steel, 14 of cast iron, 10 aluminium alloy in drilling. But the effect of thrust force could be negligible. 5. Comparison between the theoretical and experimental results showed a close agreement so far as depth of hole is about three times of drill diameter. But there was a wide difference between them beyond the rane of three times, because of characteristics of the drilling process.

• The Journal of Korean Physical Therapy
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• v.20 no.1
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• pp.11-16
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• 2008

Purpose: This study was undertaken to compare the signal characteristics of surface electromyography (EMG) between progressive resistive increase exercise (PRIE) and progressive resistive decrease exercise (PRDE). Methods: Forty healthy male subjects were randomly assigned to either the PRIE group or the PRDE group. Subjects participated in the PRIE and PRDE methods, with 10 RM for each subject. EMG activity was recorded from the rectus femoris muscle. Outcome data were collected for both groups pre-exercise, immediately post-exercise, then at 5 and 10 minutes post-exercise. Repeated measures 2-way ANOVA was used to determine the statistical difference of the root mean square (RMS) in EMG activity. Results: We showed that RMS values, when compared with pre-exercise, were decreased immediately after exercise and were increased at 5 and 10 minutes after exercise (p<0.05). The RMS values were not significantly different between the two groups (p>0.05). Conclusion: These results can indicate that both the PRIE and PRDE protocols will be improve strength with equivalent efficacy. Further studies are needed to address exercise duration, frequency of exercise sessions, and rest times than the PRIE and PRDE protocols with regard to the changes in strength improvement without a large amount of muscle fatigue.