• Journal of Wetlands Research
• /
• v.16 no.4
• /
• pp.363-370
• /
• 2014

We grew seedlings of Saechucheongbyeo and Odaebyeo of rice cultivars that are cultivated dominantly in the northern and middle regions of Korea under control(ambient condition), ambient $CO_2$ concentration+elevated temperature, and elevated $CO_2$ concentration+elevated temperature in order to study how growth responses and crop yield of major rice of Korea change as the global warming proceeds and compared the results. Aboveground biomass, belowground biomass, total biomass, and panicles weight per individual and ripended grain rate of cv. Saechucheongbyeo were the highest under control, but those of cv. Odaebyeo were the highest under elevated $CO_2$ concentration+elevated temperature. There was no difference in the number of panicles per individual of cv. Saechucheongbyeo and cv. Odaebyeo in these experiments. There was no difference in the number of grains per panicle of cv. Saechucheongbyeo among three environmental gradients, but that of cv. Odaebyeo was the highest under elevated $CO_2$ concentration+elevated temperature. Weight of a grain of cv. Saechucheongbyeo was highest under elevated $CO_2$ concentration+elevated temperature, but that of cv. Odaebyeo was the higher under ambient $CO_2$ concentration+elevated temperature and elevated $CO_2$ concentration+elevated temperature. Thus, if global warming continues in Korea, selection of rice cultivation varieties must be chosen carefully for commendation.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.32 no.4
• /
• pp.438-443
• /
• 1999

Germination and growth of Laminaria japonica microscopic stages were investigated under crossed gradients of temperatures and irradiances, and the results related to the seasonal temperature regime in the southeastern coast of Korea. Germination rates of $70\~86\%$ were observed in the temperature range of $5\~20^{\circ}C$, however, at $25^{\circ}C$ no germination of meiospores was observed. The primary factor affecting germination rates at the temperature range of $5\~20^{\circ}C$ was irradiance: germination was significantly reduced at $150 {\mu}E{\cdot}m^{-2}{\cdot}s^{-1}$. Vegetative cell production of female gametophytes was highest at $20^{\circ}C$, but plants were not fertile at the temperature. In the temperature range of $5\~15^{\circ}C$, higher irradiance caused females to reduce cell production, but increased fertility. Cell production was also low at lower temperatures with increased fertility rates. Optimal growth temperature for microsporophytes was $10^{\circ}C$ and their growth rates were light-saturated at $70 {\mu}E{\cdot}m^{-2}{\cdot}s^{-1}$. We have concluded that meiospores released before July could develope to the young sporophytic stage in the southeastern coast of Korea which is off the southern limit of its geographical distribution. However, limiting factor in the development of natural sporophytic population in this region would be the upper temperature limit for the survival of young sporophytes, as water temperature at this area frequently exceeds $25^{\circ}C$ during the summer period.

• Korean Journal of Remote Sensing
• /
• v.17 no.1
• /
• pp.1-14
• /
• 2001

The enhancement of the refractive index structure parameter $C_n^2$ often occurs where vertical gradients of virtual potential temperature ${\theta}_v$ and mixing ratio q have their maximum values. The $C_n^2$ can be a very useful parameter for estimating the convective boundary layer(CBL) height. The behavior of $C_n^2$ peaks, often used to locate the height of mixed layer, was investigated in the present study. In addition, a new method to determine the CBL height objectively using both $C_n^2$ and vertical air velocity variance ${\sigma}_w$ data of UHF radar was also suggested. The present analysis showed that the $C_n^2$ peaks in the backscatter intensity profiles often occurred not only at the top of the CBL but also at the top of a residual layer or at a cloud layer. The $C_n^2$ peaks corresponding to the CBL heights were slightly lower than the CBL heights derived from rawinsonde sounding data when vertical mixing owing to weak solar heating was not significant and the height of strong vertical ${\theta}_v$ gradients were not consistent with that of strong vertical q gradients. However, the $C_n^2$ peaks corresponding to the CBL heights were in good agreement with the rawinsonde-estimated CBL hegiths when vertical mixing owing to solar heating was significant and the vertical gradient of both ${\theta}_v$ and q in the entrainment zone was very strong. The maximum backscatter intensity method, which determines the height of $C_n^2$ peak as the CBL height, correctly estimated the CBL height when the $C_n^2$ profile had single peak, but this method erroneously estimated the CBL height when there was a residual layer or a cloud layer over the top of the CBL. The new method distinguished when there the CBL height from the peak due a cloud layer or a residual layer using both $C_n^2$ and ${\sigma}_w$ data, and correctly estimated the CBL height. As for estimation of diurnal variation of the CBL height, the new method backscatter intensity method even if the vertical profile of backscatter intensity had two peaks from the CBL height and a residual layer or a cloud layer.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.17 no.1
• /
• pp.35-49
• /
• 2014

In order to understand the impacts of surface characteristics and the distance from the urban heat island center to suburban areas on the mean night time air temperature, we analyzed GIS and AWS observational data. Spatial distributions of mean night time air temperature during the summer and winter periods of 2004-2011(six years) were utilized. Results show that the temperature gradients were different by distance and direction. We found high correlation between mean night-time air temperature and artificial land cover area within 1km and 200m radii during both summer(R=0.84) and winter(R=0.78) seasons. Regression models either from 1km and 200m land surface data explained the distribution of night-time temperature equally well if the input data had sufficient resolution with detailed attribute including building area and height.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.8
• /
• pp.1061-1070
• /
• 2003

A triple flame in a mixing layer was studied experimentally with concentration gradient and mean velocity by using a multi-slot burner, which can stabilize the lift-off flame. Flame stabilization condition, lift-off heights, and some other characteristics were examined for methane and propane flame within a range of very low concentration gradient. Pitot-tube and LDV(Laser Doppler Velocimetry) were used for velocity. Mass spectroscopy and Rayleigh scattering signal were used for concentration gradients. Thermo-couples and SiC TFP(Thin Filament Pyrometer) were used for temperature. It was found that minimum values of the lift-off heights exist at a certain concentration gradient for constant mean velocity and this means that the propagation velocity has a maximum value. The scales of flame to the burner nozzle and intensity variation of the diffusion flame were suspected as the cause.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.2
• /
• pp.316-323
• /
• 2000

A nonlinear low-Reynolds-number heat transfer model is developed to predict turbulent flow and heat transfer in separated and reattaching flows. The $k-{\varepsilon}-f_{\mu}$ model of Park and Sung (1997) is extended to a nonlinear formulation, based on the nonlinear model of Gatski and Speziale (1993). The limiting near-wall behavior is resolved by solving the $f_{\mu}$ elliptic relaxation equation. An improved explicit algebraic heat transfer model is proposed, which is achieved by applying a matrix inversion. The scalar heat fluxes are not aligned with the mean temperature gradients in separated and reattaching flows; a full diffusivity tensor model is required. The near-wall asymptotic behavior is incorporated into the $f_{\lambda}$ function in conjunction with the $f_{\mu}$ elliptic relaxation equation. Predictions of the present model are cross-checked with existing measurements and DNS data. The model preformance is shown to be satisfactory.

• Korean Journal of Environmental Biology
• /
• v.23 no.4
• /
• pp.367-373
• /
• 2005

We conducted a year-long survey in 2000 to examine seasonal fluctuations in the abundance of the demersal copepod Pseudodiaptomus sp., the dominant copepod in the Seomjin River estuary, where the spring tide strongly affects changes in salinity gradients. Pseudodiaptomus sp. was found throughout the year in the entire range of salinities measured, but most individuals appeared at oligohaline conditions below 5.0 psu, and less than $2\%$ were observed in polyhaline conditions above 18.0 psu. The peak abundance occurred during autumn in oligohaline waters, and the density was relatively low during the rainy season in summer. In spring and autumn, copepodites were most abundant in oligohaline waters, although they were also fairly abundant in mesohaline conditions $(5\~18\;psu)$. Females with egg sacs appeared in oligo- and mesohaline waters during spring and autumn but were seldom found in polyhaline conditions throughout the year. Our results indicate that, despite the strong physical influence of the tide, Pseudodiaptomus sp. can manipulate its position to remain at its preferred salinity. We also found that spawning mainly occurred in oligohaline waters twice a year.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.8
• /
• pp.1183-1190
• /
• 2002

An experimental study is performed to investigate the characteristics of near wake behind a circular cylinder with serrated fins using the constant temperature anemometer and through flow visualization. Previous report(Boo et al., 2001) shows that there are three different modes in vortex shedding behavior. This paper is focused on the identification of the physical reasons why the difference iss occured in vortex shedding. The through flow velocity crossing fins decreases as increasing fin height and decreasing fin pitch mainly due to the flow resistence. Vortex shedding is affected strongly by velocity distribution around fin tube, especially by the velocity gradient. The velocity distribution at X/d=0.0 has lower gradient with increasing freestream velocity and fin height and decreasing fin pitch. Those differences in velocity gradients generate different vortex shedding mechanism.

• Journal of the Korean Society of Safety
• /
• v.5 no.2
• /
• pp.6-16
• /
• 1990

In this paper, the natural convection in a square enclosure, partly heated from below, with two adiabatic vertical wall and one upper horigental wall is studied nomerically. In numerical study, SIMPLE(Semi-Implicit for Pressure Linked Equation) algorithems are applied for the integration of momentum and energy equation. The grid size used in this study is the coordinates of size (22$\times$22). As a result of numerical analysis, the initial fluid flow depends on the thermal diffusion, but, as time passes, the fluid flow depends on convection and buoyancy of the enclosure. In Case 1, the heating region was been in the central position of the bottom wall. In case 2, the heating region was in the left position of the bottom. In case of Case 1, the lapse time of sensing the temperature of 72$^{\circ}C$ is approximately 15 sec almost at the same time in the coordinates (6, 22), (11, 22). In case of Case 2, the lapse time in the coordinates (6, 22), (11, 22) was 27 sec, 25 sec repectively. Also in case of Case 1 or Case 2, the gradients of y-position of the two sensors are transposed each other.

• The KSFM Journal of Fluid Machinery
• /
• v.14 no.5
• /
• pp.18-23
• /
• 2011

A CFD analysis method is developed and applied for investigating the gas flow and the byproduct particle trajectory in Roots type vacuum pump. The internal fluid flow and thermal fields between the rotors and the housing of vacuum pump are analyzed by using the dynamic mesh, the numerical methods for unsteady 2-D Navier-Stokes equation and the standard k-$\varepsilon$ turbulence model of the Fluent code. Coupled with the flow simulation results, the particle trajectory of the byproduct flowing into the pump with gas stream is analyzed by using discrete phase modeling technique. The CFD analysis results show the pressure, the velocity and the temperature distributions in pump change abruptly due to the rotation of rotors, and back flows are produced due to the strong reverse pressure gradients at rotor/rotor and rotor/housing clearances. The predicted byproduct particle trajectory results also show the particles impinge on the clearance surfaces between the housing and the rotor of pump and then may form the deposit layer causing the failure of pump.