• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.9
• /
• pp.24-33
• /
• 2017

Multitemporal MODIS vegetation index (VI) data are widely used in vegetation monitoring research into environmental and climate change, since they provide a profile of vegetation activity. However, MODIS data inevitably contain disturbances caused by the presence of clouds, atmospheric variability, and instrument problems, which impede the analysis of the NDVI time series data and limit its application utility. For this reason, preprocessing to reduce the noise and reconstruct high-quality temporal data streams is required for VI analysis. In this study, a data reconstruction method for MODIS NDVI is proposed to restore bad or missing data based on the statistical properties of the oscillations in the NDVI temporal dynamics. The first derivatives enable us to examine the monotonic properties of a function in the data stream and to detect anomalous changes, such as sudden spikes and drops. In this approach, only noisy data are corrected, while the other data are left intact to preserve the detailed temporal dynamics for further VI analysis. The proposed method was successfully tested and evaluated with simulated data and NDVI time series data covering Baekdu Mountain, located in the northern part of North Korea, over the period of interest from 2006 to 2012. The results show that it can be effectively employed as a preprocessing method for data reconstruction in MODIS NDVI analysis.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.31 no.4
• /
• pp.326-339
• /
• 1995

In this paper, the validity of the numerical model of fishes' behavior presented in our earlier paper was examined by the whiteness test on the residual of numerical model and by the comparison between experiment and simulation on several indexes represented by fishes' swimming characteristics. The validity of the numerical model was proved statistically by means of the whiteness test of the residual. The similarity was confirmed by comparison between experiment and simulation for the swimming trajectory of fishes, the mean distance of individual from wall, the mean swimming speed and the mean distance between the nearest individuals. These results suggest that the behavior of fishes according to the flow speed in three-dimensional space can be estimated partially by the numerical model presented in our earlier paper. However, a long-term approach to improve the modeling technique on the behavior of fishes may be needed before applying the numerical model presented in our earlier paper to real fishing ground.

• 한국해양학회지
• /
• v.26 no.1
• /
• pp.59-66
• /
• 1991

Laboratory studies were carried out to measure the sound velocity (V/SUB p/) and quality factor (Q/SUB p/, inverse attenuation) in the horizontal (H) and vertical (V) direction on the core sampled sediment of deep-sea basin (1,850 meter water depth), East Sea of Korea (Sea of Japan). Sampled core was about 250 cm long and 500 kHz ultrasonic p-wave transducer was used for a sound soured. V/SUB p/ varies from 1,480 m/sec to 1,500 m/sec, it is not clear which direction is faster, V/SUB PH/ or V/SUB pv/, within${\pm}$ 1.0% anisotropy (A/SUB p/). It is thought because the core sediment facies is highly (or slightly) bioturbated homogeneous mud with very high porosity (more than 80%). The general trend of Q/SUB p/ is decreasing 10 to 5 with the buried depth, it is strongly affected by the variation of sediment texture (increasing silt, decreasing clay) with increasing of CaCO$_3$ and organic matter content, But Q/SUB PH/ is jumping up to 14.9 near the bottom of core sediment as including volcanic ash richly. The relationship between V/SUB PH/ and Q/SUB PH/ shows the mirror image nearly, it is interpreted that not only the geotechnical properties and texture but also sea-water characteristics (high Q/SUB p/, low V/SUB p/) according to rich water content affect strongly in the upper part of the unconsolidated deep-sea basin sediment.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.2
• /
• pp.50-57
• /
• 2007

Shocks are excited by impulsive forces and cause discomfort in vehicles. Current standards define means of evaluating shocks and predicting their discomfort, but the methods are based on research with a restricted range of shocks. This experimental study was designed to investigate the discomfort of seated subjects exposed to a wide range of vertical shocks. Shocks were produced from the responses of one degree-of-freedom models, with 16 natural frequencies (from 0.5 to 16 Hz) and four damping ratios (0.05 0.1, 0.2 and 0.4), to a hanning-windowed half-sine force inputs. Each type of shock was presented at five vibration dose values in the range $0.35\;ms^{-1.75}$ to $2.89\;ms^{-1.75}$. Fifteen subjects used magnitude estimation method to judge the discomfort of all shocks. The exponent in Stevens' power law, indicating the rate of growth in discomfort with shock magnitude, decreased with increasing fundamental frequency of the shocks. At all magnitudes, the equivalent comfort contours showed greatest sensitivity to shocks having fundamental frequencies in the range 4 to 12.5 Hz. At low magnitudes the variations in discomfort with the shock fundamental frequency were similar to the frequency weighting $W_b$ in BS 6841, but low frequency high magnitudes shocks produced greater discomfort than predicted by this weighting. At some frequencies, for the same unweighted vibration dose value, there were small but significant differences in discomfort caused by shocks having different damping ratios. The rate of increase in discomfort with increasing shock magnitude depends on the fundamental frequency of the shock. In consequence, the frequency-dependence of discomfort produced by vertical shocks depends on shock magnitude. For shocks of low and moderate discomfort, the current methods seem reasonable, but the response to higher magnitude shocks needs further investigation.

• 한국문화재보존과학회:학술대회논문집
• /
• 2001.11a
• /
• pp.27-34
• /
• 2001

Following the recommendations made by the cultural authorities the wooden cultural properties (WCP) had been treated with fire-retardants for fire protection. However, visual inspections of some of the WCPs treated with fire-retardants showed microbial decay. The work was extended to examine the micromorphological characteristics of the WCPs in a Buddhist temple which had been treated with fire-retardant. Microscopic examination showed the presence of typical soft rot cavities along the length of microfibrils in the secondary wall. Bacterial attack was also observed by scanning and transmission electron microscopy. It is interesting that the decay patterns observed in the Buddhist temple were very similar to those observed in the waterlogged woods. Presumably chemicals in the fire-retardants used rendered the wood susceptible to attack by soft-rot and bacterial decay by causing an increase in the moisture content of wood. Further studies are needed to investigate the effect of fire-retardants used currently on the hygroscopicity and the strength of wood materials in the WCPs. Microbial attacks caused degradation of the secondary cell walls and in some cases also of the middle lamella. In addition, the cell walls in the outer parts of wood were also degraded due to weathering, and cell separation occurred from total disintegration of the middle lamella.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.22 no.5
• /
• pp.463-474
• /
• 2009

Double symmetric patch repair of existing structures always causes membrane action only, however, in many cases this technique is not practical. On the other hand, the bending stiffness of the patch and the skin increases as tensile loading is increased and affects the bending deformation significantly in the case of single-sided patch repair. In this study, the p-convergent full layerwise model has been proposed to determine the stress concentration factor in the vicinity of a circular hole as well as across the thickness of plates with single-sided patch repair. In assumed displacement field, the strain-displacement relations and 3-D constitutive equations of a layer are obtained by the combination of 2-D and 3-D hierarchical shape functions. The transfinite mapping technique has been used to represent a circular boundary and Gauss-Lobatto numerical integration is implemented in order to directly obtain stresses occurred at the nodal points of each layer without other extrapolation techniques. The accuracy and simplicity of the present model are verified with comparison of the previous results in literatures using experiment and conventional 3-D finite element. Also, the bending effect has been investigated with various patch types like square, circular and annular shape.

• Journal of the Korea Society of Computer and Information
• /
• v.19 no.8
• /
• pp.35-44
• /
• 2014

This paper proposes a 3D pointing interface that is designed for the efficient application of a hand mouse. The proposed method uses depth images to secure high-quality results even in response to changes in lighting and environmental conditions and uses the normal vector of the palm of the hand to perform 3D pointing. First, the hand region is detected and tracked using the existing conventional method; based on the information thus obtained, the region of the palm is predicted and the region of interest is obtained. Once the region of interest has been identified, this region is approximated by the plane equation and the normal vector is extracted. Next, to ensure stable control, interpolation is performed using the extracted normal vector and the intersection point is detected. For stability and efficiency, the dynamic weight using the sigmoid function is applied to the above detected intersection point, and finally, this is converted into the 2D coordinate system. This paper explains the methods of detecting the region of interest and the direction vector and proposes a method of interpolating and applying the dynamic weight in order to stabilize control. Lastly, qualitative and quantitative analyses are performed on the proposed 3D pointing method to verify its ability to deliver stable control.

• Journal of the Korean earth science society
• /
• v.26 no.3
• /
• pp.253-267
• /
• 2005

Seasonal and spatial variations of tidal flat sediments were studied in Yeoja Bay. Results of the yearly observation of tidal flat transect lines indicated that the monthly change of grain size composition was not distinct from each tidal flat transect line, but it was quite clear that clay covered $40\~70\%$ of the sediment composition. Clay composed most highest in the northern part of the bay, and lowest in the western. As clay content increased, water and organic matter showed a tendency of increase, while the mean grain size was fixed per clay amount. Shear strength came out as 0 kPa as a whole. Seasonal variations of clay contents in each tidal flat were higher in winter and spring, but lower in summer and autumn. Thefine sediments were likely to be accumulated in the winter and spring. The average accumulation rate of each tidal flat was $-14.62\~38.57mm{\cdot}yr^{-1}$. The numbers showed $32.13mm{\cdot}yr^{-1}$ in the northern, $-14.62mm{\cdot}yr^{-1}$in the western, and $6.46mm{\cdot}yr^{-1}$ in the eastern part. During the coarse of this study sediment accumulation rates indicated that the sediments deposited continuously in the northern part of tidal flat, whereas erosion occurred in the western part. However, there was no distinct change in the eastern part. It was due to the clockwise lateral circulation in Yeoja Bay. Seasonally, sedimentation happened during the dry season (winter and spring) and erosion during the wet season (summer and autumn).

• Korean Journal of Food Science and Technology
• /
• v.43 no.3
• /
• pp.291-302
• /
• 2011

The effects of roasting condition and storage time on rancidity of rapeseed oil were studied. Rapeseed oil from rapeseed roasted under different conditions were stored in the dark at $17^{\circ}C$. Volatile compounds of rapeseed oil were analyzed with an electronic nose (E-nose) and gas chromatography-mass spectrometry (GC-MS). The data from the E-nose were analyzed using discriminant function analysis (DFA). As roasting temperature increased from 150 to $240^{\circ}C$ over 20 min, the first discriminant function score (DF1) moved from positive to negative. DF1 decreased with storage time and changes in DF1 were higher between 0 and 2 days and between 20 and 24 days. Twenty-four compounds were identified in rapeseed oil, and hydrocarbons, furans, ketones, acids, benzene, and aldehydes were detected by GC-MS. The number of formed volatile compounds increased as storage time increased, but no increase in these compounds was detected by GC-MS.

• Publications of The Korean Astronomical Society
• /
• v.14 no.2
• /
• pp.123-128
• /
• 1999

The beam size and the antenna efficiency of TRAO 14m radio telescope were measured at 86.2, 98.0 and 115.2 GHz. The beam size was determined by deconvolving the azimuthal scanning data of the Venus. To test the accuracy of our deconvolution method, the beam size at 86.2 GHz was compared with that determined from the mapping data of SiO maser line and we found no difference between them. With above beam sizes, antenna efficiencies were calculated from the continuum measurements of Venus, Jupiter and Moon. The beam efficiencies at these frequencies are appeared to be 0.49, 0.45 and 0.41, respectively. On the other hand, we also suggest that an automatic focus setting can be adopted for TRAO radio telescope based on the gradual change of best focus with elevation.