• Journal of the Korean institute of surface engineering
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• v.25 no.3
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• pp.144-149
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• 1992

The adsorption and molecular sieve characteristics of water, methanol, ethanol, butanol and benzene on acid-alkali treated natural zeolite from Kampo area were investigated by the Diamond·Kinter method, and it was compared with synthetic zeolite A. Adsorption amount of water increased with the treatment of acid rather than the treatment of alkali. Similar tendency was observedd in adsorption of alcohols such as methanol, ethanol and butanol, but the amount of adsorption decreased. From the views of the molecular size, adsorption amount of benzene decreased because of surface activity according to the cations species rather than chemical treatment. And it was almost same value that the amount of adsorption was compared acid treated natural zeolite with synthetic zeolite A.

• 대한치과보철학회:학술대회논문집
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• 2003.04a
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• pp.99-99
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• 2003

• Journal of the Korean GEO-environmental Society
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• v.14 no.4
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• pp.53-58
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• 2013

The design for horizontal drain layer on soft ground starts from the decision that the material could be used or not, by verifying material condition in permeability of horizontal drain material according to the weight percent of the dry soil retained on #200 sieve. In the next step of the design, we estimate the thickness of horizontal drain layer to confirm trafficability of heavy machinery in construction work. Successively, the long-term functionality for good drainage of horizontal drain layer is checked and if needed, some means are considered. In this study, the system to recycle mixed coal ash in ash pond successfully as a horizontal drain material on soft ground is presented through the process and the result of its practical construction work. Namely, the pact is confirmed that mixed coal ash in ash pond should be sorted out by sieve screen to a certain extent and the remainders of this mixed coal ash on sieve openings be recycled, because the amount of finer particles than $75{\mu}m$ contained in mixed coal ash in ash pond is quite massive and irregular depending on the coal power plant or the location in same ash pond. In order to sort at large scale in situ, the dimension of a sieve squre hole and the sort-out method, etc. should be decided before the sort-out process. And, it is described that we need to manufacture classifier to sort out mixed coal ash in ash pond, too.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.8 no.1
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• pp.115-123
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• 1998

Vinyl chloride monomer exists as gas phase at normal temperature and reacts with oxygen and strong oxidant in the air to form oxidized materials. Because of being easily synthesized, it is used as a main source at the synthetic reaction process of PVC synthesis factories. Ministry of Labor regulates its usage as a carcinogen and its exposure level as 1 ppm. But the amount of VCM production in PVC and VCM production process hasn't been exactly estimated. In addition, facilities of this factory are located in outdoor. Therefore, this study was designed to investigate effects of temperature on breakthrough of charcoal tube at a fixed concentration and temperature during VCM sampling based on NIOSH and OSHA methods which were used as methods of occupational environment measuring and analysis. During the sampling of VCM, methods of OSHA and NIOSH require flow rate of 0.05 lpm and sampling volume of $3{\ell}$, $5{\ell}$ respectively, at this time carbon molecular sieve tube and coconut shell charcoal tube are used to observe the breakthrough along with concentration and temperature. As a result, significant difference between average adsorbed amounts of OSHA methods but that of NIOSH methods cannot be found. NIOSH method is likely to be effected by high temperature and normal temperature in high concentration. Breakthrough is not found in the method of OSHA at different conditions of temperature and concentration. As the result of this study we could verify that breakthrough occurred in the process of sampling VCM with NIOSH methods. Therefor in summer time, breakthrough should be considered and research on the breakthrough volume should be done. It is considered the research about the specificity of the coconut shell charcoal and carbon molecular sieve sorbent should be done when sampling VCM in comming days.

• Journal of IKEEE
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• v.23 no.2
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• pp.438-447
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• 2019

As the IoT-based hyper-connected society grows, public-key cryptosystem such as RSA is frequently used for encryption, authentication, and digital signature. Public-key cryptosystem use very large (safe) prime numbers to ensure security against malicious attacks. Even though the performance of the device has greatly improved, the generation of a large (safe)prime is time-consuming or memory-intensive. In this paper, we propose ET-MR and ET-MR-MR using Euler sieve so it runs faster while using less memory. We present a running time prediction model by probabilistic analysis and compare time and memory of our method with conventional methods. Experimental results show that the difference between the expected running time and the measured running time is less than 4%. In addition, the fastest running time of ET-MR is 36% faster than that of TD-MR, 8.5% faster than that of DT-MR and the fastest running time of ET-MR-MR is 65.3% faster than that of TD-MR-MR and similar to that of DT-MR-MR. When k=12,381, the memory usage of ET-MR is 2.7 times more than that of DT-MR but 98.5% less than that of TD-MR and when k=65,536, the memory usage of ET-MR-MR is 98.48% less than that of TD-MR-MR and 92.8% less than that of DT-MR-MR.

• Journal of the Korean GEO-environmental Society
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• v.4 no.1
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• pp.41-48
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• 2003

This study analyzed the correlation between the engineering characteristics of soils, and the CBR values in order to figure out the eligibility of quality criteria as construction materials, by attempting to reduce time and costs for the CBR testing and predicting the results of the CBR testing. The study also analyzed the correlation between the percent passing of No.200 sieve, liquid limit and compaction characteristics, on the basis of the soil testing data conducted at the Yeongdong construction area. This study will provide necessary data for road pavement plans and designs by analyzing the correlation between the percent passing of No.200 sieve, the degree of activity and the swelling rate, and suggest the correlation formula with each soil.

• Magazine of the Korean Society of Agricultural Engineers
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• v.11 no.4
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• pp.1783-1790
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• 1969

It is one of the most economical method of soil stabilization works to compact soil, which increases soil density artificially. Compaction effort is to lessen void of soils, and consequently its aim is to enlarge friction and cohesion force, and reduce permeability of soil. Factors in compaction effort are moisture content, grain size, grain size distribution, physical properties, compaction method and temperature of soils etc. The results obtained in this study on the effects that grain size, gradation and physical properties influence upon compaction effort for 20 samples under the constant compaction method, are summarized as follows: 1. The bigger the maximum dry density is, the smaller the optimum moisture content is, on the other hand, the smaller the maximum dry densityis, the bigger the optimum moisture content is, ingeneral. 2. The coarser the grain size is, the bigger the maximum dry density is, and the optimum moisture content becomes small, and dry density-moisture content curve has the sharp peak, generally. Also, the finer the grain size is the smaller the maximum dry density is, and the optimum moisture content shows the big value, and dry density-moisture content curve has the dull peak. 3. The maximum dry density shows the biggest value on the sample to be about 15% of particles finer than No. 200 sieve. The more the percent passing of No. 10 sieve increase, the smaller the maximum dry density is. Soils which have uniformity coefficient less than 5 in particles larger than 0.074mm hardly show dry density-moisture content curve. 4. There is a relation which is ramax＝2.3948-0.0376 Wopt between the maximum dry density and the optimum moisture content, namely, the maximum dry density is increased in proportion to decrease of the optimum moisture content. 5. There are relations to be the straight lines which the maximum dry density decrease, on the other hand, the optimum moisture content increase in accordance with enlargement of Atterberg Limit(LL, PL, PL) in compacted soils.

• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.775-782
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• 2002

The effects of solid and dispersant concentration was investigated by wet-sieving method for knowing the amount of coarse particle in fine powders. In the work alumina powders, sodium hexametaphosphate and sodium polyacrylate were used for preparing slurry. It was confirmed that the coarse particle mass increased by increasing alumina concentration and decreasing dispersant concentration. With systematic measurements we know that the alumina powder and dispersant of one weight percent(1.0wt%) were proper quantity for coarse particle mass measuring, respectively. Sodium polyacrylate as dispersant showed higher coarse particle mass than sodium hexametaphosphate. The sieve mass was decreased according to increase of experiment number. Based on experiments it was considered that wet-sieving method is good tool for measuring a coarse particle mass in fine powders.

• Bulletin of the Korean Mathematical Society
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• v.55 no.6
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• pp.1659-1666
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• 2018

Let $P_r$ denote an almost-prime with at most r prime factors, counted according to multiplicity. In this paper, it is proved that for every sufficiently large even integer N, the equation $$N=x^2+p_1^2+p_2^3+p_3^3+p_4^4+p_5^4$$ is solvable with x being an almost-prime $P_4$ and the other variables primes. This result constitutes an improvement upon that of $L{\ddot{u}}$ [7].

• Journal of the Korean Institute of Gas
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• v.13 no.6
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• pp.34-38
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• 2009

Nitrous oxide, which is used as an anesthetic gas, has been shown to be a chronic health hazard. It is necessary to monitor and control the nitrous oxide exposure of the operating theaters staff. In this study, N2O exposure level of the operating nurses is assessed with a GC-ECD. The nitrous oxide gas is collected on a molecular sieve 5A contained in a glass tube and desorbed for 12 hours at $100^{\circ}C$ in heating block. As a result of the test using GC-ECD, calibration curve's $R^2$ of $N_2O$ is 0.9992, LOD is $0.96{\mu}g$/injection, LOQ is $3.21{\mu}g$/injection, desorption efficiency is 94.78 4.50% in average and break through is within 10% compared with the concentration. The average concentration before operation is 5.12ppm and it is 42.3ppm during operation. There are a significant difference showing that the P value is lower than 0.05. Assessing exposure level to nitrous oxide based on nurses' working positions, the exposure levels do not show significant difference( P>0.005). And $N_2O$ in active sampling method is higher than passive sampling method(P<0.05).