• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.4
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• pp.451-457
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• 1983

This study was conducted to estimate the effect of the drought on the changes of chlorophyll, protein and proline content of upper three leaves, and the grain yield components of barley plant (CV. baegdong) subjected to water stress at four stages: late vegetative, boot, anthesis early grain filling. 1. In comparison with leaf posititions in water stress, the first leaf below flag leaf maintained the highest relative turgidity, chlorophyll and protein content and showed the least proline accumulation. And, in terms of growth stages in water stress, chlorophyll was shown to be highest at anthesis stage, protein being highest at boot stage and proline being least at boot stage. 2. In boot stages, culm and spike length, and Number of grains per spike were remarkably decreased. And the weight of 1000 grains was at least level in the early grain filling stage, and also the grain size was comparatively decreased at boot and two following stages. 3. The protein content of grain by water stress, apart from early grain filling stage, was not significantly affected by water stress at different growth stages. 4. The rate of sterility was particularly increased at boot and anthesis stages. 5. It was eventually concluded that the boot stage among four growth stages, and the flag leaf in 3 leaf positions were mostly damaged by water stress at reproductive growth stage.

• Journal of The Korean Society of Grassland and Forage Science
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• v.13 no.1
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• pp.31-37
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• 1993

It is important to improve the germination of grass seeds because they are poor germination under water stress. This experiment was conducted to investigate the response of seeds pre-treated individually with Polyethylene glycol 6000 (PEG) and growth regulators(GA$_3$, Kinetin, NAA) on the germination characteristics when two levels of osmotic potential (0, -5 bar) were put to seeds of Orchardgrass. In the untreated seeds, the total germination rate was decreased under water stress, and the mean germination time was delayed. Priming of Orchardgrass seeds using PEG or GA$_3$ resulted in improved germination under water stress(-5 bar), whereas the opposite was true of kinetin or NAA. The response of seeds primed in solutions of either -15 bar PEG or 100 ppm GA$_3$ was particulary marked compared with the untreated seeds. It is suggested that PEG and GA$_3$ may have positive regulatory effects in triggering the system for water stress alleviation. But the inhibitory effect of the water stress was not completely removed by allowing the seeds to pre-treat in solution of PEG or GA$_3$.

• Korean Journal of Remote Sensing
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• v.39 no.6_1
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• pp.1225-1234
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• 2023

The intensity of crop water stress caused by moisture deficit is affected by growth and heat conditions. For more accurate detection of crop water stress state using remote sensing techniques, it is necessary to select vegetation indices sensitive to crop response and to understand their changes considering not only soil moisture deficit but also heat conditions. In this study, we measured the MERIS terrestrial chlorophyll index (MTCI) and chlorophyll/carotenoid index (CCI) under drought and heat wave conditions. The MTCI, sensitive to chlorophyll concentration, sensitively decreased on non-irrigation conditions and the degree was larger with heat waves. On the other hand, the CCI, correlated with photosynthesis efficiency, showed less sensitivity to water deficit but had decreased significantly with heat waves. After re-irrigation, the MTCI was increased than before damage and CCI became more sensitive to heat stress. These results are expected to contribute to evaluating the intensity of crop water stress through remote sensing techniques.

• Weed & Turfgrass Science
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• v.4 no.4
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• pp.360-367
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• 2015

This study was performed to determine the effects of silicon on zoysiagrass after the application of drought stress. The daily amount of water or scilicon solution was 150 ml per a pot. For 14 days, plants were treated with 0.1 and 1.0 mM silicon (Si) and with distilled water for control and the drought only-treatment. Afterward, the plants in Si and drought treatment were exposed to a 21-day under drought stress condition but the plants in control received water. The results indicated that the growth and the moisture and chlorophyll contents decreased in the drought only-treatment and 0.1 mM Si compared to the control. However, 1.0 mM Si showed an increase in the growth with a significant increase of water and chlorophyll contents. The MDA and $H_2O_2$ concentrations and electrolyte leakage decreased, while the radical scavenging capacity increased in 1.0 mM Si. 1.0 mM Si showed little to no differences in the growth and no differences in water and chlorophyll contents, electrolyte leakage, MDA and $H_2O_2$ concentrations and antioxidant capacity compared to the control. These results suggested that application of silicon is useful for drought tolerance improvement of zoysiagrass under drought that is occurring in turf fields.

• Journal of Animal Science and Technology
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• v.59 no.7
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• pp.13.1-13.6
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• 2017

This study was conducted to investigate the behavioral and physiological changes of heat stressed Corriedale ewes exposed to water deprivation. Nine Corriedale ewes (average $BW=45{\pm}3.7kg$) were individually fed diets based on maintenance requirements in metabolic crates. Ewes were assigned into three groups (9 sheep per treatment) according to a $3{\times}3$ Latin square design for 3 periods with 21-d duration for each period. The control (CON) group was given free access to water, 2 h water deprivation (2hWD), and 3 h water deprivation (3hWD) following feeding. No differences were found in fecal excretion frequency, standing frequency (number/d), and sitting frequency among the groups (p > 0.05). Measurements of standing duration (min/d) and urine excretion frequency (number/d) showed a significant decrease whereas sitting duration (min/d) showed a significant increase in the 2hWD and 3hWD groups when compared with the CON group (p < 0.05). Fecal score and heart rate (number/min) were not different among the groups (p > 0.05). However, respiratory rate (number/min) and panting score were found to be significantly higher in the 2hWD and 3hWD groups than in the CON group (p < 0.05). It is concluded that water deprivation following feeding intensifies physiological heat stress related indicators such as respiratory rate and panting score and changes behavioral parameters such as water intake and urine excretion frequency in heat stressed ewes. Daily adaptation to the extreme environmental conditions may occur actively in ewes.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.62-62
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• 2022

Among annual precipitation in Korea (1306.3 mm), 54% of it falls intensively in summer, and only about 12.4% falls in April and May, when the water requirement of wheat is the highest. Korean wheat also could be damaged by soil water excess stress as frozen soil thaws after winter (late Feb-Mar). This study was conducted to evaluate effect of soil water stress on yield and quality of Korean wheat cultivar 'Saegeumgang'. Soil water treatments consisted of 4 treatments; water excess treatment in tilling stage (3.23-3.30), drought treatment in ripening stage (Apr-Jun), irrigation treatment in ripening stage (5.10) and standard condition. There was no significant difference between the treatment conditions for culm length, and the number of spike number was the highest in the order of irrigation in the ripening period (951)> standard cultivation (876)> excess water treatment in the tilling stage (752)> drought treatment in the ripening stage (767/m²). Test weight and Thousand grain weight were 548g/L and 22. lg respectively, which were lower than other treatments, and there was no significant difference between the other treatments. Abortive grain was 5.4kg/10a which was lower than other treatment, and there was no significant difference between the other treatment than other treatments. In drought treatment, protein content was 11.9% which is the highest among all treatments, and SDS-sedimentation value was 27.2ml under drought treatment which was very low compared to other treatments. Therefore, wheat yield and spike number were decreased in excess water condition at tilling stage and drought condition at ripening stage. Furthermore, wheat quality became deteriorate in drought condition at ripening stage.

• The Korean Journal of Ecology
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• v.19 no.5
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• pp.453-463
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• 1996

Diurnal changes of microclimatic conditions and tissue water relations were measured at two sites where Carpinus laxiflora and C. cordata were allopatrically distributed. The microclimatic conditions at a site where C. laxiflora was distributed produced severe water stress condition during summer months. Daily maximum temperature reached $30.4^\circC$ and the highest vapor pressure deficit was 1.31 KPa when 13 rainless days were continued. During this period soil water content decreased to below the field capacity even at a depth of 20 cm and xylem pressure potential also decreased to ­2.04 MPa. However, turgor potential was maintained more than 0.4 MPa. Patterns of stomatal conductance were changed with evaporative demand and soil water availability. On the other hand, microclimatic conditions at a site where C. cordata was distributed were moderate water strees condition compared with those at a site C. laxiflora was distributed. Though soil water content was maintained above field capacity C. cordata showed a remarkable decrease in turgor potential and stomatal conductance throughout the experiment. These results indicate that there is a difference in habitat characteristics between the two species and C. laxiflora is more resistant than C. cordata to water stress.

• Tribology and Lubricants
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• v.13 no.3
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• pp.115-123
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• 1997

The electrorheological (ER) behavior of suspensions in silicone oil of silica gel powder (average particle size 49 $\mu$m) absorbed water was investigated at room temperature with electric fields up to 2.4 KV/mm. In this paper, for development of succcessful ER fluids used for wide temperature range later, we would like to know a fundamental understanding of water on ER effect. As a first step, the ER fluids involving water activated silica gel were measured not only the electrical characteristics such as dielectric constant, current density and electrical conductivity but also the rheological properties on the strength of electric field, the quantity of dispersed phase and absorbed water. From the experimental results that water absorbed to the particles directly affects to the surface charge density of electric double layer model proposed by Schwarz and makes dielectric constant and current density of ER fluids increase. The current density and dynamic yield stress $($\tau$_y)$ of water activated silica gel suspensions was in exponential proportion to the strength of electric field, the quantity of dispersed phase and absorbed water. And the optimum water quantity and weight concentration of silica gel for electrorheological effect were 4-5 wt% and 15 wt%, respectively.

• Computers and Concrete
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• v.29 no.4
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• pp.209-217
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• 2022

In order to analyze the static and dynamic structural characteristics of the Obermeyer gate under overflow conditions, the force characteristics and vibration characteristics of the shield plate structure are studied based on the fluid-solid coupling theory. In this paper, the effects of the flow rate, airbag pressure and overflow water level on the structural performance of shield plate of air shield dam are explored through the method of controlling variables. The results show that the maximum equivalent stress and total deformation of the shield plate decrease first and then increase with the flow velocity. In addition, they are positively correlated with the airbag pressure. What's more, we find that the maximum equivalent stress of the shield plate decreases first and then increases with the overflow water level, and the total deformation of the shield plate decreases with the overflow water level. What's more importantly, the natural frequency of the shield structure of the Obermeyer gate is concentrated at 50 Hz and 100 Hz, so there is still the possibility of resonance. Once the resonance occurs, the free edge of the shield vibrates back and forth. This work may provide a theoretical reference for the safe and stable operation of the shield of the Obermeyer gate.

• Journal of the Korean Geotechnical Society
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• v.27 no.1
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• pp.41-52
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• 2011

The hypothesis on effective stress of unsaturated soil is validated by $K_0$ consolidation results of triaxial tests for the compacted residual soil. The stress characteristic curve (SSCC) can describe unsaturated soil behavior on water contents, which was defined from shear strength or from soil water characteristic curves. In this study, it was found that the stress path of $K_0$ consolidation can also define the SSCC. The effective stress was defined by SSCC. $K_0$ paths for various matric suctions could be described as a unique line by effective stress. The measured values of $K_0$ were interpreted by effective stress as a constant with respect to matric suction. Since the SSCC from $K_0$ consolidation agrees with that from the shear strength, the SSCC from soil water retention curve could describe effective stress behavior consistently on both $K_0$ consolidation path and stress at failure. The effective stress based on SSCC can describe the entire unsaturated behavior from consolidation to failure.