• Geomechanics and Engineering
• /
• v.22 no.2
• /
• pp.143-152
• /
• 2020

In this research, soil samples of the Kerman sedimentary basin, Iran, were investigated through laboratory tests such as petrography (Scanning Electron Microscopy (SEM), X-Ray Fluorescence Spectroscopy (XRF) and X-Ray Diffraction (XRD)), physical and mechanical characteristics tests. The soil in this area is dominantly CL. The petrography results showed that the dominant clay mineral is Illite. This soil has made some problems in the earth dams due to the low shear strength. In this study, a set of samples were prepared by adding different amounts of lime. Next, the petrography and strength tests at the optimum moisture content were performed. The results of SEM analysis showed substantial changes in the soil structure after the addition of lime. The primary structure was porous and granular that was changed to a uniform and solid after the lime was added. According to XRD results, dominant mineral in none stabilized soil and stabilized soil are Illite and calcite, respectively. The pozzolanic reaction resulted in the reduction of clay minerals in the stabilized samples and calcite was known as the soil hardener material that led to an increase in soil strength. An increase in the hydrated lime leads to a decrease in their maximum dry unit weight and an increase in their optimum moisture content. Furthermore, increasing the hydrated lime content enhanced the Unconfined Compressive Strength (UCS) and soil's optimum moisture. An increase in the strength is significantly affected by the curing time and hydrated lime contents, as the maximum compressive strength is achieved at 7% hydrated lime. Moreover, the maximum increase in the California Bearing Ratio (CBR) achieved in clay soils mixed with 8% hydrated lime.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.2
• /
• pp.147-154
• /
• 1988

Korea has the ground which freezes in winter and melts in warmer seasons by turns. Therefore, in designing civil-structures or buildings on such ground, the depth of seasonal frost penetratio must be considered. In this paper, approximate contours of the maximum depth of frost penetration in Korea is presented. It was found that the maximum depth of frost penetration did not have the linear relationship to square root of the freezing index. In order to establish more reliable method to estimate the maximum depth of frost penetration, a new empirical equation is introduced. In the presented equation, the dry unit weight and water content of soil are considered in addition to the freezing index. And the equation is compared with other previous equations used so far.

• Journal of Korean Society of Forest Science
• /
• v.59 no.1
• /
• pp.15-30
• /
• 1983

To select the superior clones of Populus alba ${\times}$ Populus glandulosa $F_1$, growth and some growth-related physiological characters were examined for thirteen, one-year-old and fifteen, two-year-old clones, respectively at the Seoul National University nursery in Suweon, Clonal differences in growth (total dry weight per tree), leaf area per tree and leaf chlorophyll content per tree at tow-year-old plots were highly significant at the 1% level, but not at one-year-old plots, Highly significant correlation was found between leaf area per tree and total dry weigh per tree (r=0.865), between leaf chlorophyll content per tree and total dry weight per tree (r=0.888), and between photosynthetic ability per tree and total dry weight per tree (r=0.745). The photosynthetic ability and leaf chlorophyll content per unit leaf area of one-year-old plant increased with increasing leaf order number from top. reached maximum value in the twenty-eithth and thirty-third leaves, respectively, and then decreased gradually from those leaved to base, Clones 68-1-54, 66-26-55 and 65-22-11 showed test growth based on leaf area per tree, leaf chlorophyll content per unit leaf area and photosynthetic ability of leaf tissue per unit area. Growth yield of populus alba ${\times}$ P. glandulosa $F_1$ clones could be estimated from either leaf area per tree of leaf chlorophyll content per tree. Therefore, measurements of leaf area and leaf chlorophyll content appear useful to select superior populus clones early growth.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2001.10a
• /
• pp.256-260
• /
• 2001

This study was initially performed to investigate current red-pepper drying methods commonly being adopted on red-pepper cultivation farm area. Based on the informations obtained from the field survey, an experiment of red-pepper drying was carried out to verify the actual drying potential of plastic covered solar house similar to the conventional pipe frame greenhouses covered with one or two layer of plastic film. Some results obtained from field survey and drying experiment for red-pepper are summarized as follows; 1. Various patterns of red-pepper drying process were found; 1) complete natural drying with red-pepper exposed in outdoor air, 2) hot air drying by dry chamber only, 3) combination drying by hot air dryer together with plastic covered passive solar house, 4) drying with plastic covered solar house unit. 2. The average air temperatures of outdoor and solar house during drying experiment period were $26.9-30.8\;and\;28.6-33.8^{\circ}C$, respectively, and the maximum air temperatures of those two were $34.2-36.4\;and\;39.8\;-52.3^{\circ}C$, respectively. Horizontal solar intensity during experiment period was $18.49-23.96\;MJ/m^{2}$, and relative humidity of outdoor and experimental solar house were 56 - 66% and 64 - 70%, respectively. 3. The weight of red-pepper during drying experiment period was decreased almost linearly from initial moisture content of 85% to final moisture content of 14%.

• Journal of the Korean Geotechnical Society
• /
• v.40 no.3
• /
• pp.93-100
• /
• 2024

Pore water freezes in low-temperature compaction, which leads to different compaction characteristics compared to room temperature conditions. In regions like Alberta, Canada, where organic soils are prevalent, compaction performance is influenced by the high water retention and compressibility of organic soils, as well as their sensitivity to freezing and thawing. Alberta's strict environmental regulations demand the reuse of excavated soil for backfill, and the long winter season creates challenging conditions for civil engineering projects. In this study, a laboratory compaction test was conducted to evaluate the low-temperature compaction characteristics of organic soils with varying organic content. The results indicate that the optimum moisture content increases as the organic content increases, and the maximum dry unit weight decreases by up to 21.9%. In addition, under temperature conditions below -4℃, no optimum moisture content was observed, and the dry unit weight decreased as the moisture content increased.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.55 no.4
• /
• pp.275-283
• /
• 2010

This experiment was conducted to construct process models to estimate grain weight (GW) and grain nitrogen content (GN) in rice. A model was developed to describe the dynamic pattern of GW and GN during grain-filling period considering their relationships with temperature, solar radiation and growth traits such as LAI, shoot dry-weight, shoot nitrogen content, grain number during grain filling. Firstly, maximum grain weight (GWmax) and maximum grain nitrogen content (GNmax) equation was formulated in relation to Accumulated effective temperature (AET) ${\times}$ Accumulated radiation (AR) using boundary line analysis. Secondly, GW and GN equation were created by relating the difference between GW and GWmax and the difference between GN and GNmax, respectively, with growth traits. Considering the statistics such as coefficient of determination and relative root mean square of error and number of predictor variables, appropriate models for GW and GN were selected. Model for GW includes GWmax determined by AET ${\times}$ AR, shoot dry weight and grain number per unit land area as predictor variables while model for GN includes GNmax determined by AET ${\times}$ AR, shoot N content and grain number per unit land area. These models could explain the variations of GW and GN caused not only by variations of temperature and solar radiation but also by variations of growth traits due to different sowing date, nitrogen fertilization amount and row spacing with relatively high accuracy.

• Journal of Forest and Environmental Science
• /
• v.36 no.3
• /
• pp.207-218
• /
• 2020

Ashwagandha is an important ancient medicinal crops, being affected with many diseases, among which leaf blight caused by Alternaria alternata has become the constraint resulting in huge yield losses. Continuous usage of chemical methods leads to environment, soil and water pollution. Whereas biological control of diseases is long lasting, inexpensive, eco-friendly and harmless to target organisms. In this context, it is aimed to evaluate five Trichoderma strains viz. Trichoderma virens IMI-392430, T. pseudokoningii IMI-392431, T. harzianum IMI-392432, T. harzianum IMI-392433 and T. harzianum IMI-392434 as bio-control efficacy against A. alternata and growth promoting effect in Ashwagandha. All the Trichoderma strains had varied antagonistic effects against the pathogen. In dual culture technique, the strain T. harzianum IMI-392433 showed maximum percentage inhibition of mycelial growth (54.89%) followed by T. harzianum IMI-392432 (53.83%), T. harzianum IMI-392434 (48.94%) and T. virens IMI-392430, (43.62%) against the pathogen, while the least inhibition percentage was observed with the T. pseudokoningii IMI-392431 (36.60%). The culture filtrate of the Trichoderma strain, T. harzianum IMI-392433 recorded highest inhibition on the mycelial growth (39.05%) and spore germination (80.77%) of pathogen and the lowest was recorded in T. pseudokoningii IMI-392431 (20.45 and 50%). Moreover, seeds treated with spore suspension of the strain T. harzianum IMI-392433 reduced the percentages of disease severity index significantly. The strain T. harzianum IMI-392433 also significantly increased seed germination %, seedling vigor and growth of Ashwagandha. The correlation matrix showed that root yield per plant of Ashwagandha had significant and positive correlation with plant height (r=0.726^⁎⁎), number of leaf (r=0.514^⁎⁎), number of primary branch (r=0.820^⁎⁎), number of secondary branch (r=0.829^⁎⁎), fresh plant weight (r=0.887^⁎⁎), plant dry weight (r=0.613^⁎⁎), root length (r=0.824^⁎⁎), root diameter (r=0.786^⁎⁎), root dry weight (r=0.739^⁎⁎) and fresh root weight (r=0.731^⁎⁎). The significant and negative correlation (r=-0.336^⁎⁎) was observed with the root yield and percentages of disease severity index. The study recognized that the T. harzianum IMI-392433 strain performed well in inhibiting the mycelial growth and reduced the percentages of disease severity index of pathogen as well as increased the plant growth in Ashwagandha.

• Journal of the Korean Society for Railway
• /
• v.19 no.2
• /
• pp.204-212
• /
• 2016

The soils used as trackbed in Korea are selected using USCS utilizing basic soil properties such as Grain Size Distribution(GSD), % passing of #200 sieve ($P_{200}$), % passing of #4 sieve ($P_4$), Coefficient of uniformity ($C_u$), and Coefficient of curvature ($C_c$). Degree of compaction of the soils adapted in the code by KR should be evaluated by maximum dry density (${\gamma}_{d-max}$) and deformation modulus $E_{v2}$. The most important influencing factor that is critical to stability and deformation of the compacted soils used as trackbed is stiffness. Thus, it is necessary to construct a correlation between the modulus and the basic soil properties of trackbed soil in order to redefine a new soil classification system adaptable only to railway construction. To construct the relationship, basic soil test data is collected as a database, including GSD, maximum dry unit weight (${\gamma}_{d-max}$), OMC, $P_{200}$, $P_4$, $C_u$, $C_c$, etc.; deformation modulus $E_{v2}$ and $E_{vd}$ are obtained independently by performing a Repeated Plated Bearing Test (RPBT) and Light Weight Deflectometer Test (LWDT) for ten different railway construction sites. A linear regression analysis is performed using SPSS to obtain the relationship between the basic soil properties and the deformation modulus $E_{v2}$ and $E_v$. Based on the constructed relationship and the various obtained mechanical test data, a new soil classification system will be proposed later as a guideline for the design and construction of trackbed foundation in Korea.

• Journal of the Korea Institute of Building Construction
• /
• v.18 no.3
• /
• pp.211-218
• /
• 2018

This study examined the reliability and revision necessity of concrete standard specifications based on the comparisons with test data obtained by using domestic artificial lightweight aggregates and the contents specified in different foreign specifications including ACI 211.2, ACI 213, ACI 301, JASS 5 and CEB-FIP. To achieve the continuous particle distribution of domestic fine lightweight aggregates, the partial addition of natural sand with the maximum size of 2.5mm was required. To control the segregation and excessive bleeding in the fresh lightweight concrete, the current limitations on the water-to-binder ratio and unit water content need to be modified using lower values. In particular, a rational mixture proportion approach of lightweight concrete needs to be established for the targeted requirements of initial slump, 28-day compressive strength, air content and dry unit weight. Ultimately, significant revision of the concrete standard specifications is required considering the characteristics of domestic artificial lightweight aggregates.

• Journal of Plant Biology
• /
• v.26 no.1
• /
• pp.17-32
• /
• 1983

The aboveground production, nutrient distribution and nutrient cyclings were compared between two Phragmites communis communities growing in the different salt contents of soil in a coastal salt marsh. Inorganic nutrient contents of soil for plant growth were greater at the low salt stand than at the high salt stand except for sodium(Na). Maximum aboveground biomass of the plant at the low and the high salt stands were 2,533 and 1,719 g dw/$m^2$, respectively, in August. Seasonal changes of nutrient content of biomass in dry weight decreased with growth except for Na. Nutrient contents in biomass per unit land area increased continuously as biomass increases, although the amount of potassium(K) reached the maximum content in July and thereafter decreased. Vertical distributions of total nitrogen(T-N) and phosphorus(P) increased with plant height, but Na showed the reverse trend. That of K was similar to the patterns for T-N and P in the leaves, and to the pattern of Na in the stems. The Na was greatly accumulated in underground biomass but transported scarcely to aboveground. At the low and the high salt stands, the ratios of the inorganic nutrients contained in the plant were 100 : 66 for T-N, 100 : 61 for P, 100 : 62 for K and 100 : 97 for Na. the ratios of the amounts of nutrients retrieved to soil were 100 : 242 for T-N, 100 : 408 for P, 100 : 127 for K and 100 : 269 for Na, respectively. Turnover times of the T-N, P, K and Na in the communities were 56, 1, 15 and 174 years at the low salt stand, and 75, 2, 24 and 323 years at the high salt stand, respectively. In nutrient cyclings, all of the nutrients retrieving to soil were less than uptake by plant. Among the nutrient, especially P is expected to be exhausted from soil, sooner or later, because of the harvest by men.