• Geomechanics and Engineering
• /
• v.30 no.2
• /
• pp.201-210
• /
• 2022

This paper presents a study regarding the influence of various water levels on the characteristics of subgrade mud pumping through a self-developed test instrument. The characteristics of mud pumping are primarily reflected by axial strain, excess pore water pressure, and fine particle migration. The results show that the axial strain increases nonlinearly with an increase in cycles number; however, the increasing rate gradually decreases, thus, an empirical model for calculating the axial strain of the samples is presented. The excess pore water pressure increases rapidly first and then decreases slowly with an increase in cycles number. Furthermore, the dynamic stress within the soil first rapidly decreases and then eventually slows. The results indicate that the axial strain, excess pore water pressure, and the height and weight of the migrated fine particles decrease significantly with a low water level. In this study, when the water level is 50 mm lower than the subgrade soil surface, the issue of subgrade mud pumping no longer exist.

• Journal of Advanced Marine Engineering and Technology
• /
• v.26 no.1
• /
• pp.59-67
• /
• 2002

The comparison of $J_{Rice}$-resistance considering a few strength ratio in Rice J-integral formula and $J_{\delta}$-resistance curves converted from experimental CTOD using appropriate strength chosen according to strain hardening level, n=10.6 (A533B steel) and n=8.1 (BS4360 steel) is carried out. The optimal dimensionless strength ratio like the factor of revision, (see full text)reflecting strain hardening level in Rice\`s experimental formula is found out and the reliability of appropriate reference strength chosen according to strain hardening level in different materials is investigated through doing that CTOD is transformed from $J_{\delta}$-integral using relationship between J-integral and CTOD. The results are as follows; 1) The optimal factor of revision is when m equals to 3 in (see full text) for Rice's and the above optimal factor of revision multiplies by coefficient, η in Rice's experimental formula instead of n=2, 2) and the pertinent reference strength for high strain hardening material like BS4360 steel is ultimate strength, $\sigma_{u}$ and for material like A533B steel is ultimate-flow strength, $\sigma_{u-f}$. The incompatible of the behavior of both experimental J-resistance curves using Rice's formula and CTOD-resistance curves for A533B and BS4360 steel by Gordon, et al., could be corrected using the optimal factor of revision in Rice\`s and the pertinent reference strength in J=$m_{j}$${\times}$$\sigma_{i}$${\times}$CTOD.

• International Journal of Oral Biology
• /
• v.45 no.2
• /
• pp.70-75
• /
• 2020

The aim of this study was to identify strain KCOM 1265 isolated from subgingival plaque at the species level by comparing 16S ribosomal RNA gene (16S rDNA) and genome sequences. The whole genome of strain KCOM 1265 was extracted using the phenol-chloroform extraction method. 16S rDNA was amplified using polymerase chain reaction and sequenced using the dideoxy chain termination method. Pairwise genome comparison was performed using average nucleotide identity (ANI) and genome-to-genome distance (GGD) analyses. The data showed that the percent similarity of 16S rDNA sequence of strain KCOM 1265 was 99.6% as compared with those of Fusobacterium polymorphum ATCC 10953^T and Fusobacterium hwasookii KCOM 1249^T. The ANI values of strain KCOM 1265 with F. polymorphum ATCC 10953^T and F. hwasookii KCOM 1249^T were 95.8% and 93.0%, respectively. The GGD values of strain KCOM 1265 with F. polymorphum ATCC 10953^T and F. hwasookii KCOM 1249^T were 63.9% and 49.6%, respectively. These results indicate that strain KCOM 1265 belongs to F. polymorphum.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.11a
• /
• pp.335-342
• /
• 2000

In this study, the swelling characteristics of reconstituted clayey soil were investigated by STD and CRS test. The strain rate during loading was constant i.e. 0.05 %/min, 0.03 %/min and during unloading was varied in proportion to 1/1, 1/5, 1/10 and 1/15 of strain rate during loading. From this study the following conclusions were obtained; (1) There were similar values, especially, during unloading in case of 1/10 or 1/15 of strain rate during loading and the test results between STD and CRS were much to be alike. (2) The cross point of effective stress versus excess pore water pressure ratio curve, was increased during unloading, while the stress level of the cross point was decreased. The stress level can be separated into two zones according to the swelling index named Cs1 and Cs2. From the test results, the values of Cs1 were approximately constant irrespective of strain rate during unloading, but the values of Cs2 were much influenced by strain rate. (3) In CRS consolidation tests, it was found that unloading strain rate did not affect on the existence of zone.

• Journal of Microbiology
• /
• v.38 no.3
• /
• pp.160-168
• /
• 2000

A-factor I a microbial hormone that can positively control cell differentiation leading to spore formation and secondary metabolite formation in Streptomyces griseus. to identify a protease that is deeply involved in the morphological and physiological differentiation of Streptomyces, the proteases produced by Streptomyces griseus IFO 13350 and its A-factor deficient mutant strain, Streptomyces griseus HH1, as well as Streptomyces griseus HH1 transformed with the afsA gene were sturdied. In general Streptomyces griseus showed a higher degree of cell growth and protease activity in proportion to its ability to produce a higher amount of A-factor. In particular, the specific activity of the trypsin of Streptomyces griseus IFO 13350 was greatly enhanced more than twice compared with that of Streptomyces griseus HH1 in the later stage of growth. The specific activity of the metalloprotease of Streptomyces griseus HH1 was greatly enhanced more than twice compared with that of Streptomyces griseus IFO 13350, and this observation was reversed in the presence of thiostreptione, However, Streptomyces griseus HH1 transformed with the afsA gene showed a significantly decreased level of trypsin and metalloprotease activity compared with that of the HH1 strain. There was no significant difference between Streptomyces griseus IFO 13350 and HH1 strain in their chymotrypsin and thiol protease activity, yet the level of leu-amionpeptidase activity was 2 times higher in Streptomyces griseus HH1 than in strain IFO 13350 . Streptomyces griseus HH1 harboring afsA showed a similar level of enzyme activity , however, all the three protease activities sharply increased and the thiol protease activity was critically increased at the end of the fermentation. When a serine protease inhibitor, pefabloc SC, and metalloprotease inhibitor, EDTA, were applied to strain IFO 13350 to examine the in vivo effects of the protease inhibitors on the morpholofical differentiation, the formation of aerial meycelium and spores was delayed by two or three days.

• Journal of Ocean Engineering and Technology
• /
• v.28 no.2
• /
• pp.133-139
• /
• 2014

Offshore wind turbines have been constructed extensively throughout the world. These turbines are subjected to approximately $10^8$ horizontal load cycles produced from wind, waves, and current during their lifetimes. Therefore, the accumulated displacement of the foundation under horizontal cyclic loading has significant effects on the foundation design of a wind turbine. Akili(2006) and Achmus et al.(2009) performed cyclic triaxial tests on dry sands and proposed an empirical model for predicting the accumulated plastic strain of sands under long-term cyclic loading. In this study, cyclic triaxial tests were performed to analyze the cyclic loading behaviors of dry sands. A total of 27 test cases were performed by varying three parameters: the relative density of the sands, cyclic load level, and confining stress. The test results showed that the accumulated plastic strain increased with an increase in the cyclic load level and a decrease in the relative density of the sand. The confining stress had less effect on the plastic strain. In addition, the plastic strain at the 1st loading cycle was about 57% of the accumulated strain at 1,000 cycles. Finally, the input parameters of the empirical models of Akili(2006) and Achmus et al.(2009) were evaluated by using the relative density of the sand and the cyclic load level.

• International Journal of Railway
• /
• v.8 no.2
• /
• pp.50-54
• /
• 2015

The primary function of the trackbed in a conventional railway track system is to decrease the stresses in the subgrade to be in an acceptable level. A properly designed trackbed layer performs this task adequately. Many design procedures have used assumed and/or are based on critical stiffness values of the layers obtained mostly in the field to calculate an appropriate thickness of the sublayers of the trackbed foundation. However, those stiffness values do not consider strain levels clearly and precisely in the layers. This study proposes a method of computation of stiffness that can handle with strain level in the layers of the trackbed foundation in order to provide properly selected design values of the stiffness of the layers. The shear modulus values are dependent on shear strain level so that the strain levels generated in the subgrade in the trackbed under wheel loading and below plate of Repeated Plate Bearing Test (RPBT) are investigated by finite element analysis program ABAQUS and PLAXIS programs. The strain levels generated in the subgrade from RPBT are compared to those values from RC (Resonant Column) test after some consideration of strain levels and stress consideration. For comparison of shear modulus G obtained from RC test and stiffness moduli $E_{v2}$ obtained from RPBT in the field, many numbers of mid-size RC tests in laboratory and RPBT in field were performed extensively. It was found in this study that there is a big difference in stiffness modulus when the converted $E_{v2}$ values were compared to those values of RC test. It is verified in this study that it is necessary to use precise and increased loading steps to construct nonlinear curves from RPBT in order to get correct $E_{v2}$ values in proper strain levels.

• Korean Journal of Microbiology
• /
• v.18 no.2
• /
• pp.51-58
• /
• 1980

Mutational experiments were performed to improved to improve the protease productivity of Aspergillus flavus KU 153, which is selected among the wild strains. A UV-induced mutant strain having high protease productivity was obtained by the use of the clear zone method as a simple criterion for a primary screening test. Neutral and alkaline protease activities of hte mutant strain were higher than 1.8 times, comopared with those of the parental strain, respectively, while in the case of acid protease, it was 2.7 times. The mutant strain selected was more powerful in the production of cellulase and amylase, as well s protease in wheat bran, compared with those of the parental strain. protease production of the parental strain has reached maximum level at 3 days culture, while alkaline nad neutral protease production of the mutantstrain has reached at 2 days culture. On the other hand, the mutant strain formed the spore slowly, compared with the parental strain. Column chromatography of the neutral protease on DEAE-Sephadex A-50 showed that the mutant strain was not induced the formation of another neutral protease isozyme, but induced the variation in the function of regulatory gene.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.55 no.2
• /
• pp.1-8
• /
• 2013

This study was performed for the purpose of analyzing the effect of tide on the stress-strain behavior in the boundary surface of sea dike embankment. Tide is a dynamic condition, but there are not suitable numerical models to solve the dynamic embankment condition caused by tide. So the analysis was simplified to quasi dynamic as follow. First, seepage by tide was analyzed according to elapsed time, and the results of the analysis at every hour during one periodic cycle time of 12 hours were applied to the pore water pressure conditions of stress-strain analysis with hyperbolic model by Duncan and Chang. The place at which maximum shear strain took place in the analysis result moved up and down repeatedly along the boundary of the dredged sand fill section and the crashed stone filter section. The value of maximum shear strain was large at high water level of tide. This result means that contraction and relaxation occur in turn repeatedly at every specific position along the boundary, and the repeated action compact loose position with sand moved down from the upper position by gravity. The experiment with the small sea dike model showed the result consistent with the numerical analysis. The surface of sea side on the dike collapsed at high water level after a couple of repetition of the rising and falling of water.

• Geomechanics and Engineering
• /
• v.32 no.5
• /
• pp.495-502
• /
• 2023

In this study, stress relaxation tests were carried out by keeping silt type soil specimens under different strain levels. Decreases in the stress values with time data was collected to better understand the effect of the strain level on the relaxation properties of soil specimens. In addition, the stress relaxation effect on the uniaxial compressive strength (UCS) values of the specimens was investigated with a series of tests. According to the results obtained from this study, the UCS values of the silt specimens significantly vary as a result of the stress relaxation effect. The UCS values were determined to increase with an increase of relaxation strain level to a threshold value. On the other hand, the UCS values were found to be affected adversely in case of high stress levels at the initiation of the relaxation, which are close to the peak level.