• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.28 no.3
• /
• pp.305-309
• /
• 1983

To know the effect of desaltation in the reclaimed tidal fields on the succession of vegetation and on the root hair formation of paddy rice, reclaimed fields in Kang Hwa Island, Nam-Yang Bay and Ke-Hwa Island were investigated during summer crop season in 1982. The obtained results can be summarized as followings. l) In the highly salty and water logged areas of reclaimed tidal fields, the first dominating species of higher plant were observed to be Salicornia herbacea L. and Suaeda japonica Makino. With the continued desaltation, Chemopodium virgatum Thumb. occurred in the vegetation. After this transition, the dominating species were composed of Scirpus maitimus L. and Phragmites communis Trin. At the S. maitimus and P. communis dominating salinity level, rice cultivation was safe from the salt damage. 2) In the water logged area, Artemisia capillaria Thunb. and Aster tripolium L. took the place of dominating species after S. herbacea and S. japonica. At this salinity level, graminaceous weeds began to immigrate. 3) In dry areas, Suaeda asparagoides Makino and Suaeda maritima were the first appearing dominant species. Atriplex subcordata Kitakawa was also observed in sucy dry areas, but colony formation was not observed. 4) Plants immigrated slowly into dry areas from the already vegetated water logged areas with the continuation of desaltation. 5) The high soil salinity level affected the root hair formation of rice by reducing both the rate of root hair formation and the length of root hairs.

• Journal of the Korean GEO-environmental Society
• /
• v.24 no.2
• /
• pp.31-40
• /
• 2023

We installed temporary strong motion seismometers at the ground surface, 1 m, 2 m, and 9 m at an existing seismic station that houses permanent seismometers installed at 20 m and 100 m, to investigate the influence of installation depth on the recorded ambient and anthropogenic noise level and the characteristics of earthquake signals. Analysis of the ambient noise shows that anthropogenic noise dominates where vibration period T < 1 s at the studied site, whereas wind speed appears to be strongly correlated with the noise level at T > 1 s. Frequency-wavenumber analysis of 2D seismometer array suggests that ambient noise in short periods are predominantly body waves, rather than surface waves. The level of ambient noise was low at 9 m and 20 m, but strong amplification of noise level at T < 0.1 s was observed at the shallow seismometers. Both the active-source test result and the recorded earthquake data demonstrated that the signal level is decreased with the increase of depth. Our result also shows that recorded motions at the ground and 1 m are strongly amplified at 20 Hz (T = 0.05 s), likely due to the resonance of the 3 m thick soil layer. This study demonstrates that analysis of ambient and active-source vibration may help find optimal installation depth of strong motion seismometers. We expect that further research considering various noise environments and geological conditions will be helpful in establishing a guideline for optimal installation of strong motion seismometers.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.42 no.2
• /
• pp.228-235
• /
• 1997

This experiments were conducted to determine the effect of allelopathy and autotoxicity in alfalfa. Among several alfalfa cultivars, the substances exudated from seven cultivars including Medicago sativa, c.v. Luna, Sparta, Magnum, Husky, Milkmaker, Challenger and Anchor inhibited the germination and seedling growth of radish, ranging from 60 to 80％. When allelopathic substances were exudated from the soil of the alfalfa-cultivated field, the increased levels of substance retarded the germination rate and seedling growth of radish and alfalfa. The inhibition rate was about 80％, compared with that of control. Thus, this study indicates that the allelopathy and autotoxicity substances of alfalfa influenced the germination and seedling growth in alfalfa itself and radish. When allelopathic substances were analysed by using gas chromatograph, several kinds of phenol compounds were detected as follows; Salicylic acid, hydroxybenzoic acid, vanillic acid, syringic acid, coumaric acid, and ferulic acid.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.22 no.2
• /
• pp.121-127
• /
• 1977

Leaf burning due to nitrofenapplication was characterized as brown color spot appearing on the leaf sheath and blade. The spots predominantly appeared around 5-7 cm high above soil surface regardless of different particle size, formulation, application method, or water level. Magnitude and frequency of burn spots increased somewhat as the granular size gets finer, by higher water level, or in transplanted rice compared to directly sown rice when applied at 7 leaf-stage, but there was no indication of increase in leaf burning due to clinging of floating dust to rice plant. When collections from local distributor's stock of TOK 7G, a granular formulation of nitrofen, were analyzed for particle size composition, 98.9% by weight ranged between 9 to 35 meshes, and only about 0.08% by weight was of particles finer than 100 mesh.

• Microbiology and Biotechnology Letters
• /
• v.50 no.4
• /
• pp.557-562
• /
• 2022

In this study we evaluated biohydrogen production potential as operational parameters (substrate, salt concentration, and temperature) using eight inoculum sources. While the volumetric biohydrogen production rate was significantly affected by temperature and inoculum sources, substrate and salt concentration did not have a significant effect on the biohydrogen production. Mesophilic temperature (37℃) was also found more appropriate for the hydrogen production than thermophilic temperature (50℃). Rate, while the eight inoculum sources, anaerobic digestion sludge exhibited the fastest biohydrogen production. The maximum production rate from anaerobic digestion sludge was 2,729 and 1,385 ml-H₂·l^-1·d^-1 at mesophilic and thermophilic temperature, respectively.

• Journal of Practical Agriculture & Fisheries Research
• /
• v.15 no.1
• /
• pp.63-73
• /
• 2013

The research was conducted to determine a seed germination and seedling establishment of rice plant under seed coating materials such as iron, silicate, and phyllite and under covered with silicate and iron coated & silicate covered in the puddled wet hill seeding and wet line seeding methods. The seedling establishment was high in silicate and untreated control of 100%>phyllite coating of 91.5%>silicate coating of 88%>iron coating and silicate covered of 86%>silicate covered of 75.5% in the puddled wet hill seeding method, respectively. At 35days after treatment there was high in seedling height at silicate covered of 23.8cm>control of 23.6cm>silicate coating of 21.4cm>phyllite coating of 20.2cm>iron coating and silicate covered of 16.8cm>iron coating of 15.4cm. In puddle wet line seeding method rice seedling establishment was high at control and silicate covered of 100%>iron coating and silicate covered by 97.5%>phyllite coating by 94.8%>iron coating by 86%. Seedling height was high in silicate covered of 22.1cm>control of 21.2cm>silicate coating of 20.0cm>phyllite coating of 19.0cm>iron coating of 17.7cm>iron coating and silicate covered of 17.0cm, respectively.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.5
• /
• pp.75-86
• /
• 2009

Salt, one of the most common soluble materials in engineering soil, may have an effect on mechanical behaviors of soils under its cementation process. In order to investigate this natural phenomenon, non-soluble material by using glass beads is mixed with salt electrolyte and cemented by using oven to evaporate water. Three different sizes of glass bead particles, 0.26, 0.5, and 1.29 mm, with different salt concentration, 0, 0.1, 0.2, 0.5, 1.0, and 2.0M, are explored by using P- and S-waves, excited by bender elements and piezo disk elemets, respectively. The velocities of the P-wave and S-wave of the particulate medium cemented by salt show three stages with the degree of saturation: 1) S-wave velocities increase while P-wave velocities reduce with degree of saturation changing from 100% to 90%; 2) Both velocities are stable with degree of saturation varying from 90% to 10%; 3) The velocities change enormously when the specimens are nearly dry with degree of saturation from 10% to 0%. Besides, the resonance frequencies of S-wave show similar stages to the S-wave velocities. This study demonstrates meaningful trends of elastic wave characteristics of geo-materials according to the cementation of dissolved salt.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.11
• /
• pp.121-131
• /
• 2008

In constructing a slurry trench cutoff wall, bentonite-water slurry is used to secure the stability of sidewalls during excavation before the wall is completed by backfilling. Unexpectedly, a thin but relatively impermeable layer called filter cake can be formed on the excavation surface, which significantly influences the result of slug test analysis in the cutoff wall if not considered. This study is to examine the effect of filter cake on evaluating hydraulic conductivity of the vertical cutoff wall through slug test analysis with the aid of the verified numerical program Slug_3D. The no-flux boundary conditions were adopted in Slug_3D to simulate the filter cake on the interface between the wall and the natural soil. A new set of type curves were built for applying the type curve method. New modification factors were obtained for using the modified line-fitting method. With consideration of filter cake, the type curve method and the modified line-fitting method were adopted to reanalyze the case study taken from EMCON (1995). The previous results achieved by Choi and Daniel (2006) without consideration of filter cake were compared with the present results obtained in this paper. The comparison emphasizes the necessity of considering filter cake when analyzing slug test results in vertical cutoff walls.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.4
• /
• pp.95-104
• /
• 2006

For the interests in the economical and safe design of foundation system, the concern on the piled raft or disconnected piled raft foundation system is increasing now. In this study, the behavior and the effects of the disconnected piled raft foundation not studied actively in this country were examined using the triaxial compression tests in place of laboratory model tests. The triaxial test samples were prepared with Jumunjin standard sand and the carbon rods, which simulate the ground soil and piles respectively. After the sample in which carbon rods were arranged was laid inside the triaxial chamber, the confining pressure was applied and then loading test was conducted. To analyze the reinforcing effects of the disconnected piled raft foundation, a few number of tests were carried out by changing the number, the diameter and the length of the model piles. As a result of this study, in the disconnected piled raft foundation system, even though the number of pile is few and the diameter of pile is small, the settlement of the foundation system decreased greatly.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.5
• /
• pp.77-88
• /
• 2007

Lateral earth pressure and horizontal displacement of the diaphragm walls constructed in multi-soil layers were analyzed by the field instrumentation from six building construction sites in urban area. The distribution of the developed earth pressure of the anchored diaphragm walls during excavation shows approximately a trapezoid diagram. The maximum earth pressure of anchored diaphragm walls corresponds to $0.45{\gamma}H$ and the earth pressure acts at the upper part of the walls. The maximum earth pressure is two times larger than the empirical earth pressure of flexible walls in sands suggested by Terzaghi and Peck(1967), Tschebotarioff(1973), and Hong and Yun(1995a). The horizontal displacement of diaphragm walls is closely related with supporting systems such as struts, anchors, and so on. The horizontal displacement of anchored walls shows less than 0.1 percent of the excavated depth, and the horizontal displacement of strutted walls shows less than 0.25 percent of the excavated depth. Therefore, the restraining effect of horizontal displacement to the anchored diaphragm walls is larger than the strutted diaphragm walls. In addition, since the horizontal displacement of the diaphragm walls is lower than the criterion, $\delta=0.25%H$, used for control the anchored retention wall using soilder piles, the safety of excavation sites applied with the diaphragm walls is pretty excellent.