• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.7
• /
• pp.342-347
• /
• 2016

This study examined the effects of the coarse aggregate maximum size and grading of fine aggregates to acquire the characteristics of very low shrinkage on normal strength concrete mixed in the field. In addition, the shrinkage characteristics of concrete under construction were evaluated in accordance with the curing temperature. The compressive strength and drying shrinkage tests were performed for nine mixing factors composed of the coarse aggregate size (13, 20, and 25 mm), types of fine aggregate (see sand, crushed sand, and blended sand), and curing temperatures (5, 20, and $35^{\circ}C$). To acquire low shrinkage properties under $350{\mu}{\varepsilon}$ strain on normal strength concrete, a 25 mm maximum of coarse aggregate was available, and the grading of fine aggregate affected the shrinkage of concrete. In addition, very low shrinkage properties were acquired in the curing temperature range except cold and hot weather concrete.

• Journal of the Korean Society for Railway
• /
• v.10 no.6
• /
• pp.701-708
• /
• 2007

A tilting train, which was developed to run the curve section without reducing the speed and compromising the riding quality, can improve the speed so as to reduce the travel time, compared to the existing trains. Then the force generated by the train operation to the track is in proportion to train operation speed, which means the track shall bear the increased force as much as the increase in train operation speed. Particularly, wheel load and lateral wheel load generated by train operation and distributed to the rail tend to cause the track to suffer the strain and furthermore the severe disaster such as derailment. To deal with such problem and ensure the train will run safety and stably, the tolerance in wheel load change, lateral wheel load and derailment coefficient was determined for quantitative evaluation of the train operation stability. In this study, derailment coefficient of inner and outer rail at existing curve section of tilting train was determined to evaluate the curve radius, possibility of acceleration and the need of rail improvement, which was then compared with the existing traditional train and high speed train. Conducting the quantitative evaluation of dynamic wheel load and lateral wheel load of each train, which was based on field survey, derailment coefficient and static & dynamic wheel load change, which serve the evaluation criteria of train operation stability, were determined for comparison with the standards, thereby analyzing the stability of the tilting train.

• Korean Journal of Plant Resources
• /
• v.26 no.1
• /
• pp.19-25
• /
• 2013

This study focused on the usefulness of plant extracts for a city organic farm. Insecticidal activity of 8 plant species, plants crude extracts by ethanol and water, against third instar larvae (susceptible strain) of Plutella xylostella was evaluated in this study. Ethanol(25%) extracts of plant materials had better insecticidal activity than water extracts at the room temperature. Insecticidal activity were investigated by leaf disc spray method. Five plant extracts (Capsicum annuum, Chelidoniun majus, Leonurus sibiricus, Coptis japonica, Mentha piperascens) showed over 50% insecticidal activity to P. xylostella at the concentration of $1500mg{\cdot}L^{-1}$. Extract of C. annuum showed the highest insecticidal activity (83.3%) against P. xylostella. Phytotoxicity was not observed on Raphanus sativus and Brassica campestris with spray application. Seed germination and growth of two plants were not affected. Extract of C. japonica revealed 73.3% control efficacy against P. xylostella of R. sativus and showed 70% control efficacy against those of B. campestris, respectively, in plastic house. Insecticidal activity against various insects was observed in C. japonica extract as 87.4% for R. sativus and 74.3% for B. campestris in the field. These results suggested that extracts of C. annuum, C. japonica showed the highest insecticidal activity, and could be used as city farm insecticides for organic farming.

• Korean Journal of Microbiology
• /
• v.48 no.2
• /
• pp.116-124
• /
• 2012

Identification was performed in March 2008 for the 76 Enterococcus strains isolated from the Han-river, which is used as water supply for Seoul citizens. The antibiotic susceptibility, antibiotic resistant structural analysis, trans-conjugation, pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) were also carried out for the isolated strains. Among the isolated strains, 25 strains were E. casseliflavus, 4 strains were E. faecalis and 1 strain was E. hirae. Investigation of antibiotic susceptibility indicated that 15 strains demonstrated tolerance against vancomycin, and that 11 strains of E. faecium and 4 strains of E. casseliflavus were VRE. The vanA gene detection of the VRE strains revealed that 6 E. faecium strains were vancomycin-resistant Enterococcus faecium (VREF) possessing vanA. Analyses of transposon Tn1546 structure containing vanA demonstrated that Km36 and Km37 belonged to Tn1 type, Km20 and Km38 was Tn2 type, and Km39 and Km40 was Tn3 type. PFGE disclosed that among the 6 VREF strains, Km36 and Km37 exhibited equivalent subtype, while the rest 4 strains showed subtypes different to each other. MLST for the 6 VREF strains disclosed that 3 strains were ST78, while the rest 3 strains were ST18, ST192 and ST230, respectively. All these clonal complexes were derived from CC17 which has been isolated from clinical sources. 4 strains belonged to CC78, while the rest 2 strains were CC18 and CC192, respectively.

• Journal of the Korean Geotechnical Society
• /
• v.30 no.4
• /
• pp.35-45
• /
• 2014

Limit equilibrium methods of slope stability analysis have been widely adopted mainly due to their simplicity and applicability. However, the conventional methods may not give reliable and convincing results for various geological conditions such as nonhomogeneous and anisotropic soils. Also, they do not take into account soil slope history nor the initial state of stress, for example excavation or fill placement. In contrast to the limit equilibrium analysis, the analysis of deformation and stress distribution by finite element method can deal with the complex loading sequence and the growth of inelastic zone with time. This paper proposes a technique to determine the critical slip surface as well as to calculate the factor of safety for shallow failure on partially saturated soil slope. Based on the effective stress field in finite element analysis, all stresses are estimated at each Gaussian point of elements. The search strategy for a noncircular critical slip surface along weak points is appropriate for rainfall-induced shallow slope failure. The change of unit weight by seepage force has an effect on the horizontal and vertical displacements on the soil slope. The Drucker-Prager failure criterion was adopted for stress-strain relation to calculate coupling hydraulic and mechanical behavior of the partially saturated soil slope.

• Korean journal of applied entomology
• /
• v.28 no.1
• /
• pp.16-22
• /
• 1989

A series of experiments was undertaken to learn bionomics and gowt plant resistance of the seedcorn maggot, Delia platura(Meigen), under controlled(24$\pm$$2^{\circ}C$, RH70$\pm$5%, and LD 16:8h)and field conditions. The preoviposition period for the flies was 9 days. The females survived for an average of 50(3-77) and the males for 24(1-59) days. A greater proportion of flies emerged between 6:00 A.M. and 9:00 A.M., soon after the sun rise. After the over-wintering, adults started to emerge in mid-April from pupae located near the soil surface, and peaked in late April by others located deeper. The sex ratio was about 1:1 with total samples of 1,609 females and 1,641 males. Weight of pupae reared from onion was heavier than those from other diets in the laboratory, however its size was samller than that of natural flies. Considerably more eggs were laid near pea seeds than other hosts tested. Among beans, Bapmitkong with blue seed-coat and a cowpea bean strain were preferred for oviposition. 'Namcheon` cultivar was found to be susceptible to attack by the larvae in the laboratory.

• Korean Journal of Poultry Science
• /
• v.35 no.1
• /
• pp.9-13
• /
• 2008

Salmonella enterica serotype gallinarum biovar Gallinarum or Pullorum and Salmonella enterica serotype Enteritidis are the most important diseases in poultry industry. Transitional diagnosis methods of these diseases such as direct isolation and identification by a biochemical test are time consuming with low specificity. In this study, we have focused on the suitable procedure for the rapid and accurate diagnosis of diseases derived from the three Salmonella strains. We initially confirmed Salmonella species by PCR using a specific ITSF/ITSR primer pair instead of biochemical test, and then the PCR-amplified phase 1 flagellin (fliC) using a specific fliCF/fliCR primer pair was digested with a restriction endonuclease, Bpm I and/or Bfa I, to discriminate among S. Pullorum, S. Gallinarum, and S. Enteritidis. We found that these methods could be applied to field isolates of the three Salmonella strains to detect and to discriminate rapidly for convenient diagnosis.

• Korean Journal of Agricultural Science
• /
• v.9 no.2
• /
• pp.569-575
• /
• 1982

Mechanical properties of rice plants were tested to determine compressive force, bending force, tensile force and shear force for improvement of harvesting machines and for efficient utilization of rice culm during the proper harvesting period. Rice varieties used in this study were two Japonica varieties with Irri 348 and Jinju, and two $Indica{\times}Japonica$ hybrids with Seogwang and Taebaeg, which were grown in the standard fertilization field of Chungnam Rural Development Office. Also Jinju and Taebaeg were tested to elucidate the shearing characteristics which included shear force-strain relationship, shear force and shear energy according to the position from the ground level, the shearing angle to the rice culm, and the moisture content. 1. Compressive force, bending force, tensile force and shear force were higher In Japonica varieties than $Indica{\times}Japonica$ hybrids. 2. Shear force to overall culm length decreased progressively to upper positions in Jinju variety but a constant shear force was approximately showed between the ground level and the position of 21cm in Taebaeg variety. 3. Shear force and shear energy increased with increase of the cross sectional area, and the rates of increase were high in general up to the cross sectional area of $10mm^2$ and then they became dull very much. 4. Shear force and shear energy decreased with decrease of moisture content of rice culm after cutting up to the moisture content of 60% (w. b.) and then they did not change significantly.

• Korean Journal of Agricultural Science
• /
• v.23 no.1
• /
• pp.25-38
• /
• 1996

To investigate the stability problem of irrigation-drainage channel excavation slope on soft ground, analyzed the behavior of the soft ground with excavation slope by the limit equilibrium method and the finite element method, and compared with field tests. The results of this study were summarized as follows; 1. When rapid drawdown the water level, the crack was occurred by the effect of the excess pore water pressure, and the pore water pressure was decreased slowly. 2. As the width of excavation was larger, the crack width was larger. And, excavated depth was deeper, the progressive failure was appeared. 3. When the soft ground excavation was small-scale, the minimum safety factor was more effected by cohesion(1.0, 1.5, 2.0, 2.5, 3.0) than excavated slope inclination(1:l, 1:1.5, 1:2). 4. As excavation was progressed, the settlement occurred on the top-slope due to plastic domain, and heaving was occurred at the bottom of excavation. 5. The maximum shear stress was appeared greatly as the base part of slope went down. Because of the increase of the maximum shear stress, tension area occurred and local failure possibility was increased. 6. As the excavation depth was increased, the maximum shear strain was appeared greatly at the base of slope and distribution pattern was concentrated beneath the middle of slope.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.22 no.5
• /
• pp.463-474
• /
• 2009

Double symmetric patch repair of existing structures always causes membrane action only, however, in many cases this technique is not practical. On the other hand, the bending stiffness of the patch and the skin increases as tensile loading is increased and affects the bending deformation significantly in the case of single-sided patch repair. In this study, the p-convergent full layerwise model has been proposed to determine the stress concentration factor in the vicinity of a circular hole as well as across the thickness of plates with single-sided patch repair. In assumed displacement field, the strain-displacement relations and 3-D constitutive equations of a layer are obtained by the combination of 2-D and 3-D hierarchical shape functions. The transfinite mapping technique has been used to represent a circular boundary and Gauss-Lobatto numerical integration is implemented in order to directly obtain stresses occurred at the nodal points of each layer without other extrapolation techniques. The accuracy and simplicity of the present model are verified with comparison of the previous results in literatures using experiment and conventional 3-D finite element. Also, the bending effect has been investigated with various patch types like square, circular and annular shape.