• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.18-23
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• 1992

Three solid acid catalysts developed recently are reviewed. Cloverite is a gallophosphate molecular sieve with very large pore, titanium silicate has a specific structure compared with conventional molecular sieves, and Envirocat is prepared for the replacement of aluminium chloride catalyst.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1254-1259
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• 2008

Recently, centrifuge tests have been widely used as tools in geotechnical engineering researches in domestic and foreign. However, the size of these centrifuge facilities is very large and thus the tests require for long time, high expense, and many labors. In this study, therefore, a small capacity(2g ton) of instructional centrifuge, which can conduct tests in a short period of time effectively, was introduced. The results of centrifuge tests conducted on the retaining wall both passive and active cases was used. Medium size of sand was used with sieve off fines in sand using #40 sieve. Based on the test results, this centrifuge facility introduced in here can be enough used for geotechnical engineering education for graduate and undergraduate students.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.5
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• pp.1121-1130
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• 2016

RSA cryptosystem is one of the most widely used public key cryptosystem. The security of RSA cryptosystem is based on hardness of factoring large number and hence there are ongoing attempt to factor RSA modulus. General Number Field Sieve (GNFS) is currently the fastest known method for factoring large numbers so that CADO-NFS - publicly well-known software that was used to factor RSA-704 - is also based on GNFS. However, one disadvantage is that CADO-NFS could not always select the optimal polynomial for given parameters. In this paper, we analyze CADO-NFS's polynomial selection stage. We propose modified polynomial selection using Chinese Remainder Theorem and Euclidean Distance. In this way, we can always select polynomial better than original version of CADO-NFS and expected to use for factoring RSA-1024.

• 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 Ginseng Research
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• v.5 no.2
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• pp.85-91
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• 1981

Ginseng seeds were gathered from 3,4,5 and 6 years of age and were classified into four qroups (below 4mm, 4∼5mm, 5∼6mm and above 6mm in across sieve). They were sown in seedling bed and some characters were investigated in each qroup of seed size. 1. The distribution of seed size of below 4mm, 4-5mm, 5-6mm and 6mm were 23.7%, 60.8%, 12.4% and 4.5%, respectively. 2. The ratio of seed coat dehiscence was not affected by seed size but emergence ratio and emerging vigor were superior in large seed. 3. The large seed showed superiority in stem length, stem diameter, leat and also in root length, root diameter and root weight. but diseased root was not affected by seed size. The effect of age(seed harvest) was not significant on all those characters.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.3
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• pp.246-253
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• 1999

Grain size distributions of sediment samples were analyzed by the different methods, and the results were compared. Reported data of the bottom sediments from the Korean seas show significant deviations among the institutes, and the inter-lab comparison and calibration procedures are considered to be necessary. Grain size data by different methods show different results. Laser diffraction method provides good precision in replicate analysis, but underestimates the amounts of finer (smaller than 2-3 ${\mu}m$) fraction. Data from particle settling method, on the other hand, represent significant errors in the coarse silt (5-6 ${\phi}$) fraction, and slightly overestimate the clay fraction. In the sieve and pipette methods, best results were taken in 0.5 ${\phi}$ interval of analysis. Especially in the coarse silt fraction, pipette analysis is suggested to be made with 0.5 ${\phi}$ interval. During the dry sieving procedure in 1 ${\phi}$ interval, serious errors occur when large amounts of sample materials were concentrated in a particular sieve.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.2
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• pp.389-423
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• 1998

This investigation was designed to determine the effectiveness of the posterior occlusal schemes on masticatory activity during mastication in complete denture. Twelve edentulous subjects were selected for this study. All subjects had no past history and no functional abnormality on masticatory system and TMjoint. And, they had residual ridge of favorable morphology, firm mucosa and Class I skeletal jaw relationship, Twelve experimental denture with interchangeable occlusions(0-degree teeth, 30-degree teeth, Levin teeth and S-A teeth) were constructed for this study. The masticatory performance was analyzed by means of standard sieve(10, 16, 20, 30sieve), and the electrical activity from selected muscles(Temporalis and Masseter muscle) was recorded simultaneously with electromyography (Bio-Pak system) as the subject masticated test foods (rice, peanut and gum) with four different occlusal schemes. Mandibular movement was, also, measured with Sirognathography(Bio-Pak system). These recordings were performed in immediately, after 1 week and after 2 weeks of insertion of complete denture. The results were as fellows; 1. The average masticatory performance of 0-degree artificial teeth was higher than any other artificial teeth. 2. Masticatory performance in denture wearer was affected preferentially by food and artificial occlusal schemes. 3. During chewing, there was a statistical difference of EMG activity between masseter and temporal muscle(p<0.01). Especially, EMG activity of working masticatory muscle was highly affected by food rather than by artificial occlusal schemes. 4. In denture wearer, the velocity of opening was not affected by food, whereas, the velocity of closing was faster in soft food chewing than in hard food chewing, and the amount of vertical displacement was grater in chewing of soft and large bolus than in chewing of hard and small bolus. However, the amount of lateral displacement showed conversely(p<0.05). 5. It was considered that masticatory performance in denture wearer is not affected by the condition of residual ridge. the history of denture wear, the preference, the adaptation to artificial teeth and the total mesiodistal length of artificial posterior teeth.

• Korean journal of food and cookery science
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• v.17 no.4
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• pp.309-315
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• 2001

The effects of soaking time of nonwaxy rice and particle size of rice flour on the properties of nonwaxy rice flour after steeping at room temperature were investigated. Nonwaxy rice was soaked at 20$^{\circ}C$ for 0, 1, 12, or 24hr, dried at room temperature and milled. Nonwaxy rice flours were passed through 45 mesh or 100 mesh sieve, and were compared for the properties depending on the particle size and soaking time. The particles of rice flour were separated into 10$\mu\textrm{m}$∼30$\mu\textrm{m}$ and 40$\mu\textrm{m}$∼80$\mu\textrm{m}$ groups, and the amount of large particle size(40$\mu\textrm{m}$∼80$\mu\textrm{m}$) was greater in the flour sieved through 45 mesh than 100 mesh sieve. The protein and ash contents decreased and amylose contents increased as the soaking time increased. The water-binding capacity increased rapidly up to 1 hr of soaking and increased slowly thereafter. The swelling power and the solubility increased with temperature rising in the range of 65$^{\circ}C$∼95$^{\circ}C$, and these two properties increased rapidly up to 12 hr of soaking. Peak viscosity and breakdown of the pastes prepared with 12 hr-soaked nonwaxy rice flour were higher than those with 1 hr-soaked ones, while the setback and viscosity at 95$^{\circ}C$ of 12 hr-soaked ones were lower than 1hr-soaked ones.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.3
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• pp.631-643
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• 2016

Currently, General Number Field Sieve(GNFS) is known as the most efficient way for factoring large numbers. CADO-NFS is an open software based on GNFS, that was used to factor RSA-704. Polynomial selection in CADO-NFS can be divided into two stages - polynomial selection, and optimization of selected polynomial. However, optimization of selected polynomial in CADO-NFS is an immense procedure which takes 90% of time in total polynomial selection. In this paper, we introduce modification of optimization stage in CADO-NFS. We implemented precomputation table and modified optimization algorithm to reduce redundant calculation for faster optimization. As a result, we select same polynomial as CADO-NFS, with approximately 40% decrease in time.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.183-189
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• 2009

The track structure of Gyungbu High Speed Railway line from Daegu to Busan is concrete track. It has a very strict specification for residual settlement because of its rigid type structural characteristics. The residual settlement of it comes from the residual settlement of the subgrade and the ground. The residual settlement of railway subgrade composed of crushed rock and soil might be major parts of total residual settlement depending on the field compaction qualities. Therefore, it is a key to minimize the residual settlement of the subgrade for a successful concrete track construction. In this paper, total 31 large scale compaction tests were performed to understand the compaction behaviors of the crushed rock-soil mixture. The test specimens were constituted with soil, crushed shale and mudstone taken from two sites under construction. The compaction tests were performed with the variations of rock types, #4 sieve passing contents, maximum particle size, and moisture contents. The influence of those factors on maximum dry unit weights of crushed rock-soil mixture was evaluated.