Planetary Boundary Layer Height (PBLH) is a major input parameter for weather forecasting and atmosphere diffusion models. In order to estimate the sub-grid scale variability of PBLH, we need to monitor PBLH data with high spatio-temporal resolution. Accordingly, we introduce a LIdar observation VEhicle (LIVE), and analyze PBLH derived from the lidar loaded in LIVE. PBLH estimated from LIVE shows high correlations with those estimated from both WRF model ($R^2=0.68$) and radiosonde ($R^2=0.72$). However, PBLH from lidar tend to be overestimated in comparison with those from both WRF and radiosonde because lidar appears to detect height of Residual Layer (RL) as PBLH which is overall below near the overlap height (< 300 m). PBLH from lidar with 10 min time resolution shows typical diurnal variation since it grows up after sunrise and reaches the maximum after 2 hours of sun culmination. The average growth rate of PBLH during the analysis period (2014/06/26 ~ 30) is 1.79 (-2.9 ~ 5.7) m $min^{-1}$. In addition, the lidar signal measured from moving LIVE shows that there is very low noise in comparison with that from the stationary observation. The PBLH from LIVE is 1065 m, similar to the value (1150 m) derived from the radiosonde launched at Sokcho. This study suggests that LIVE can observe continuous and reliable PBLH with high resolution in both stationary and mobile systems.
Numerical simulation in exploration geophysics provides important insights into subsurface wave propagation phenomena. Although elastic wave simulations take longer to compute than acoustic simulations, an elastic simulator can construct more realistic wavefields including shear components. Therefore, it is suitable for exploration of the responses of elastic bodies. To overcome the long duration of the calculations, we use a Graphic Processing Unit (GPU) to accelerate the elastic wave simulation. Because a GPU has many processors and a wide memory bandwidth, we can use it in a parallelised computing architecture. The GPU board used in this study is an NVIDIA Tesla C1060, which has 240 processors and a 102 GB/s memory bandwidth. Despite the availability of a parallel computing architecture (CUDA), developed by NVIDIA, we must optimise the usage of the different types of memory on the GPU device, and the sequence of calculations, to obtain a significant speedup of the computation. In this study, we simulate two- (2D) and threedimensional (3D) elastic wave propagation using the Finite-Difference Time-Domain (FDTD) method on GPUs. In the wave propagation simulation, we adopt the staggered-grid method, which is one of the conventional FD schemes, since this method can achieve sufficient accuracy for use in numerical modelling in geophysics. Our simulator optimises the usage of memory on the GPU device to reduce data access times, and uses faster memory as much as possible. This is a key factor in GPU computing. By using one GPU device and optimising its memory usage, we improved the computation time by more than 14 times in the 2D simulation, and over six times in the 3D simulation, compared with one CPU. Furthermore, by using three GPUs, we succeeded in accelerating the 3D simulation 10 times.
Journal of the Korean Society for Marine Environment & Energy
/
v.10
no.2
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pp.67-85
/
2007
A three-dimensional hydrodynamic model with the fine grid is applied to simulate the barotropic tides, tidal currents, residual currents and salinity dispersions in the Yellow Sea and the East China Sea. Data inputs include seasonal hydrography, mean wind and river input, and oceanic tides. Computed tidal distributions of four major tides($M_2,\;S_2,\;K_1$ and $O_1$) are presented and results are in good agreement with the observations in the domain. The model reproduces well the tidal charts. The tidal residual current is relatively strong around west coast of Korea including the Cheju Island and southern coast of China. The current by $M_2$ has a maximum speed of 10 cm/s in the vicinity of Cheju Island with a anti-clockwise circulation in the Yellow Sea. General tendency of the current, however, is to flow eastward in the South Sea. Surface residual current simulated with $M_2$ and with $M_2+S_2+K_1+O_1$ tidal forcing shows slightly different patterns in the East China Sea. The model shows that the southerly wind reduces the southward current created by freshwater discharge. In summer during high runoff(mean discharge about $50,000\;m^3/s$ of Yangtze), low salinity plume-like structure(with S < 30.0 psu) extending some 160 km toward the northeast and Changjiang Diluted Water(CDW), below salinity 26 psu, was found within about 95 km. The offshore dispersion of the Changjiang outflow water is enhanced by the prevailing southerly wind. It is estimated that the inertia of the river discharge cannot exclusively reach the around sea of Cheju Island. It is noted that spatial and temporal distribution of salinity and the other materials are controlled by mixture of Changjiang discharge, prevailing wind, advection by flowing warm current and tidal current.
The Journal of Korean Society for Radiation Therapy
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v.27
no.2
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pp.115-122
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2015
Purpose : The aim of this study, evaluate the accuracy of HeaxPOD evo RT system using the non-coplanar beam. Materials and Methods : 13 treatment plans are used which applied non-coplanar beams and 10 treatment plans which coplanar beams are used. the correction value what adjust to 6D couch is determined by each patient's setup errors only rotation direction. The study executed followings. first, Applying the correction value, measure the point dose and calculate the ${\gamma}$-index(${\gamma}=3%$ / 3 mm, ${\gamma}=2%$ / 2 mm). second, acquire data as previous methods without correction by HexaPOD. Results : For comparing the two results, we find out the more precise applying HexaPOD by point dose 0.2% in coplanar and non-coplanar. in the case of ${\gamma}$-index<1(${\gamma}=3%$ / 3 mm), more precise 2.2% in coplanar and 7% in Non-coplanar. Particularly, ${\gamma}$-index<1(2% / 2 mm) show the difference 9.2% in coplanar and 15.1% non-coplanar between apply HexaPOD and dose not apply HexaPOD. Conclusion : Using the HexaPOD is more precise than without HexaPOD. It suggests that HexaPOD evo RT system is very useful for precise and high dose delivery.
Retinal prosthesis is regarded as the most feasible method for the blind caused by retinal diseases such as retinitis pigmentosa (RP) or age related macular degeneration (AMD). Recently Korean consortium launched for developing retinal prosthesis. One of the prerequisites for the success of retinal prosthesis is the optimization of the electrical stimuli applied through the prosthesis. Since electrical characteristics of degenerate retina are expected to differ from those of normal retina, we performed voltage stimulation experiment both in normal and degenerate retina to provide a guideline for the optimization of electrical stimulation for the upcoming prosthesis. After isolation of retina, retinal patch was attached with the ganglion cell side facing the surface of microelectrode arrays (MEA). $8{\times}8$ grid layout MEA (electrode diameter: $30{\mu}m$, electrode spacing: $200{\mu}m$, and impedance: $50k{\Omega}$ at 1 kHz) was used to record in-vitro retinal ganglion cell activity. Mono-polar electrical stimulation was applied through one of the 60 MEA channel, and the remaining channels were used for recording. The electrical stimulus was a constant voltage, charge-balanced biphasic, anodic-first square wave pulse without interphase delay, and 50 trains of pulse was applied with a period of 2 sec. Different electrical stimuli were applied. First, pulse amplitude was varied (voltage: $0.5{\sim}3.0V$). Second, pulse duration was varied $(100{\sim}1,200{\mu}s)$. Evoked responses were analyzed by PSTH from averaged data with 50 trials. Charge density was calculated with Ohm's and Coulomb's law. In normal retina, by varying the pulse amplitude from 0.5 to 3V with fixed duration of $500{\mu}s$, the threshold level for reliable ganglion cell response was found at 1.5V. The calculated threshold of charge density was $2.123mC/cm^2$. By varying the pulse duration from 100 to $1,200{\mu}s$ with fixed amplitude of 2V, the threshold level was found at $300{\mu}s$. The calculated threhold of charge density was $1.698mC/cm^2$. Even after the block of ON-pathway with L-(1)-2-amino-4-phosphonobutyric acid (APB), electrical stimulus evoked ganglion cell activities. In this APB-induced degenerate retina, by varying the pulse duration from 100 to $1200{\mu}s$ with fixed voltage of 2 V, the threshold level was found at $300{\mu}s$, which is the same with normal retina. More experiment with APB-induced degenerate retina is needed to make a clear comparison of threshold of charge density between normal and degenerate retina.
Korean Journal of Agricultural and Forest Meteorology
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v.3
no.4
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pp.199-205
/
2001
This study was conducted to figure out temperature profiles of a partially developed paddy rice canopy, which are necessary to run plant disease forecasting models. Air temperature over and within the developing rice canopy was monitored from one month after transplanting (June 29) to just before heading (August 24) in 1999 and 2001. During the study period, the temporal march of the within-canopy profile was analyzed and an empirical formula was developed for simulating the profile. A partially developed rice canopy temperature seemed to be controlled mainly by the ambient temperature above the canopy and the water temperature beneath the canopy, and to some extent by the solar altitude, resulting in alternating isothermal and inversion structures. On sunny days, air temperature at the height of maximum leafages was increased at the same rate as the ambient temperature above the canopy after sunrise. Below the height, the temperature increase was delayed until the solar noon. Air temperature near the water surface varied much less than those of the outer- and the upper-canopy, which kept increasing by the time of daily maximum temperature observed at the nearby synoptic station. After sunset, cooling rate is much less at the lower canopy, resulting in an isothermal profile at around the midnight. A fairly consistent drop in temperature at rice paddies compared with the nearby synoptic weather stations across geographic areas and time of day was found. According to this result, a cooling by 0.6 to 1.2$^{\circ}C$ is expected over paddy rice fields compared with the officially reported temperature during the summer months. An empirical equation for simulating the temperature profile was formulated from the field observations. Given the temperature estimates at 150 cm above the canopy and the maximum deviation at the lowest layer, air temperature at any height within the canopy can be predicted by this equation. As an application, temperature surfaces at several heights within rice fields were produced over the southwestern plains in Korea at a 1 km by 1km grid spacing, where rice paddies were identified by a satellite image analysis. The outer canopy temperature was prepared by a lapse rate corrected spatial interpolation of the synoptic temperature observations combined with the hourly cooling rate over the rice paddies.
Korean Journal of Agricultural and Forest Meteorology
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v.6
no.2
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pp.107-117
/
2004
If doubtlessly contributes much to agriculture and rural development. The roles can be summarized as; 1. to activate rural areas and to provide more comfortable and safe rural life with equivalent services to those in urban areas, facilitating distance education, tole-medicine, remote public services, remote entertainment etc. 2. To initiate new agricultural and rural business such as e-commerce, real estate business for satellite officies, rural tourism and virtual corporation of small-scale farms. 3. To support policy-making and evaluation on optimal farm production, disaster management, effective agro-environmental resource management etc., providing tools such as GIS. 4. To improve farm management and farming technologies by efficient farm management, risk management, effective information or knowledge transfer etc., realizing competitive and sustainable farming with safe products. 5. To provide systems and tools to secure food traceability and reliability that has been an emerging issue concerning farm products since serious contamination such as BSE and chicken flu was detected. 6. To take an important and key role for industrialization of farming or lam business enterprise, combining the above roles.
Do, Min Seock;Lee, Jin-Won;Jang, Hoan-Jin;Kim, Dae-In;Yoo, Jeong-Chil
Korean Journal of Environment and Ecology
/
v.30
no.2
/
pp.173-184
/
2016
Knowledge of the relationships among interspecific competition, spatial distributions and ecological niches plays an important role in understanding biogeographical distribution patterns of species. In this study, the distributional characteristics and ecological niches of the three Viperidae species (Gloydius ussuriensis, G. brevicaudus, and G. saxatilis) in South Korea were determined based on observation data and species distribution model. The effects of interspecific competition on geographical distribution and the division of the ecological niches of the vipers were also examined based on the models of predicted species distribution. The results showed that altitude was the most important environmental variable for their distribution, and the altitudes at which these snakes were distributed correlated with the climate of that region. Although interspecific ecological niches are quite overlapped, their predicted distribution patternsvary by the Taebaek Mountains. When overlaying the distribution models, most of the overlapping habitats were forest areas, which were relatively less overlapped than were the entire research areas. Thus, a parapatric distribution pattern was expected. The abundance of species occurring sympatrically was positively correlated with each other, indicating the lack of serious interspecies competition in this region. In conclusion, although the three Viperidae species in South Korea occupy similar ecological niches, these snakes exhibit parapatric distribution patterns without direct competition. Further research on various geographic variables (e.g., altitude, microhabitat characteristics) using relatively fine grid sizes, as well as further detailed ecological and behavioral research, is needed to determine the causative factors for the parapatric distribution pattern.
To identify the detailed attenuation structure in the southern Korean Peninsula, a numerical test was conducted for the Q tomography inversion to be applied to the accumulated dataset until 2005. In particular, the stochastic pointsource ground-motion model (STGM model; Boore, 2003) was adopted for the 2D Q tomography inversion for direct application to simulating the strong ground-motion. Simultaneous inversion of the STGM model parameters with a regional single Q model was performed to evaluate the source and site effects which were necessary to generate an artificial dataset for the numerical test. The artificial dataset consists of simulated Fourier spectra that resemble the real data in the magnitude-distance-frequency-error distribution except replacement of the regional single Q model with a checkerboard type of high and low values of laterally varying Q models. The total number of Q blocks used for the checkerboard test was 75 (grid size of $35{\times}44km^2$ for Q blocks); Q functional form of $Q_0f^{\eta}$ ($Q_0$=100 or 500, 0.0 < ${\eta}$ < 1.0) was assigned to each Q block for the checkerboard test. The checkerboard test has been implemented in three steps. At the first step, the initial values of Q-values for 75 blocks were estimated. At the second step, the site amplification function was estimated by using the initial guess of A(f) which is the mean site amplification functions (Yun and Suh, 2007) for the site class. The last step is to invert the tomographic Q-values of 75 blocks based on the results of the first and second steps. As a result of the checkerboard test, it was demonstrated that Q-values could be robustly estimated by using the 2D Q tomography inversion method even in the presence of perturbed source and site effects from the true input model.
A pattern of tropical cyclone (TC) movement in the western North Pacific area was studied using the empirical orthogonal function (EOF) and the best track data from 1951 to 2007. The independent variable used in this study was defined as the frequency of tropical cyclone passage in 5 by 5 degree grid. The $1^{st}$, $2^{nd}$ and $3^{rd}$ modes were the east-west, north-south and diagonal variation patterns. Based on the time series of each component, the signs of first and second mode changed in 1997 and 1991, respectively, which seems to be related to the fact that the passage frequency was higher in the South China Sea for 20 years before 1990s, and recent 20 years in the East Asian area. When the eigen vectors were negative values in the first and second modes and TC moves into the western North Pacific, TC was formed mainly at the east side relatively compared to the case of the positive eigen vectors. The first mode seems to relate to the pressure pattern at the south of Lake Baikal, the second mode the variation pattern around $30^{\circ}N$, and the third mode the pressure pattern around Japan. The first mode was also closely related to the ENSO and negatively related to the $Ni\tilde{n}o$-3.4 index in the correlation analysis with SST anomalies.
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