• Journal of Korean Society for Atmospheric Environment
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• v.28 no.5
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• pp.595-605
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• 2012

Fine particles ($PM_{2.5}$) were collected and analyzed from April 2010 through January 2011 in Chungju to investigate the characteristics of $PM_{2.5}$ and its ionic species. The annual mean concentrations of $PM_{2.5}$, ${SO_4}^{2-}$, $NO_3{^-}$, and $NH_4{^+}$ in the particulate phase were 40.84, 7.61, 7.14 and $3.74{\mu}g/m^3$, respectively. $PM_{2.5}$ concentrations were higher in fall and spring than in winter and summer. The elevated concentrations episodes are the main factor that enhanced the $PM_{2.5}$ concentrations in the fall. Among the major ionic species ${SO_4}^{2-}$ showed the highest concentration, followed by $NO_3{^-}$ and $NH_4{^+}$, $NO_3^-$ exhibited higher concentrations during the winter, but ${SO_4}^{2-}$ and $NH_4{^+}$ were not showed seasonal variation. The high correlations were found among $PM_{2.5}$, ${SO_4}^{2-}$, $NO_3{^-}$ and $NH_4{^+}$ during all seasons except for spring. The evaluation of backward trajectories and meteorological records show that the highest $PM_{2.5}$ concentration levels occurred during W-NW weather conditions, which influenced by the emission sources of China area. The low pollution levels generally occurred during E-S weather conditions, which influenced by the East Sea and south of the Yellow Sea. The elevated $PM_{2.5}$ mass concentrations arouse the concentration of $NO_3{^-}$, but no effects on ${SO_4}^{2-}$ and $NH_4{^+}$.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.2
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• pp.14-23
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• 1998

The present study investigates numerically particle laden flow through compressor cascade. In general, a lot of turbine engines are affected by various particles which are suspending in the atmosphere. Especially in the case of aircraft aviating in volcanic, industrial and desert region including many particles, each components of engine system are damaged severely. That damage modes are erosion of compressor binding and rotor path components, partial or total blockage of cooling passage and engine control system degradation.. Initial damages can not be serious but cumulation of damages influences on safety of aircraft control and economical maintenance cost of engine system can be increased. When dust, materials and volcanic particles in the atmosphere flow in the compressor, it is necessary to predict damaged and deposited region of compressor blades. To the various flow inlet angle, predictions of particles trajectory in compressor cascade by Lagrangian method are presented and impulses by impaction of particles at blade surface are calculated. By the definition of particle deposition efficiency, characteristics of particles impact are considered quantitatively. With these prediction and experimental data, erosion rates are predicted for two materials - ceramic, soft metal - on compressor blade surface. Improvements like coating of blade surface could be found, by above prediction.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.3
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• pp.45-51
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• 2016

Existing real-time signal control system was brought up typical problems which are supersaturated condition, point detection system and loop detection system. For that reason, the next generation signal control system of advanced form is required. Following thesis aimed at calculating queue length for the next generation signal control system to utilize basic parameter of signal control in crossing queue instead of the volume of real-time through traffic. Overflow saturated condition which was appeared as limit of existing system was focused to set-up range. Real-time location information of individual vehicle which is collected by GPS data. It converted into the coordinate to apply shock wave model with an linear equation that is extracted by regression model applied by a least square. Through the calculated queue length and link length by contrast, If queue length exceed the link, queue of downstream intersection is included as queue length that upstream queue vehicle is judeged as affecting downstream intersection. In result of operating correlation analysis among link travel time to judge confidence of extracted queue length, Both of links were shown over 0.9 values. It is appeared that both of links are highly correlated. Following research is significant using real-time data to calculate queue length and contributing to signal control system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.533-541
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• 2007

The Zienkiewicz-Zhu(Z/Z) error estimate is slightly modified for the hierarchical p-refinement, and is then applied to L-shaped plates subjected to bending to demonstrate its effectiveness. An adaptive procedure in finite element analysis is presented by p-refinement of meshes in conjunction with a posteriori error estimator that is based on the superconvergent patch recovery(SPR) technique. The modified Z/Z error estimate p-refinement is different from the conventional approach because the high order shape functions based on integrals of Legendre polynomials are used to interpolate displacements within an element, on the other hand, the same order of basis function based on Pascal's triangle tree is also used to interpolate recovered stresses. The least-square method is used to fit a polynomial to the stresses computed at the sampling points. The strategy of finding a nearly optimal distribution of polynomial degrees on a fixed finite element mesh is discussed such that a particular element has to be refined automatically to obtain an acceptable level of accuracy by increasing p-levels non-uniformly or selectively. It is noted that the error decreases rapidly with an increase in the number of degrees of freedom and the sequences of p-distributions obtained by the proposed error indicator closely follow the optimal trajectory.

• Journal of Biosystems Engineering
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• v.7 no.1
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• pp.17-32
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• 1982

The binders introduced in Korea were originally designed to be used for Japonica-type varieties which have relatively long stem and are highly resistant to shattering. In order to use it for Tongil varieties which are short and easy to be shattered, mechanical modifications are necessary to reduce a grain loss incurred during binder operation. This study was intended to investigate analytically and experimentally the major sources of grain losses caused by three kinds of binders now introduced in Korea. Actual modification for each of three binders was done and experimentally compared to see if any improvement on grain loss was achieved. The results obtained in this study are summarized as follows; 1. It was required that the power transmission of binder should have a shifting mechanism so that velocities of pick-up and traveling units could be changed independently as desired according to the Japonica-type and Tongil varieties. In other words, the desired velocity of traveling unit should be obtained by shifting the transmission and the velocity of pick-up unit should be selected by reaping clutch according to the variety independent of the velocity of traveling unit as shown in Fig. 6. 2. To reduce grain loss it was desired that the moving parts of the pick-up unit should have the lowest possible velocities in harvesting Tongil varieties, unless the reduction of the speed be hindered the conveyance of the material. Based on the study, it was concluded that the velocities of pick-up unit be reduced by about 35% of those of the existing units. 3. It was found that the lug at the upper rotating section of pick-up case gave a severe impact on the ears of rice to increase grain loss. The optimum design of pick-up case to protect the ears from the protruding part of the lug was recommended by the result of analysis of the trajectory of the end-point of lug at the position. 4. It was proved analytically and experimentally that pick-up unit at the lower-rotating part was the other important source of grain loss in pick-up and divider assembly. In order to reduce a grain loss incurred by lugs at their lower-rotating section, it was suggested to improve it by (1) widening the space between right and left lower-rotating section, (2) shortening the length of lugs, (3) enlargement of the angle between the pick-up case and ground-level, and (4) attaching guard to right and left dividers so that the rotating lug could not give a high impact to the paddy hill. 5. Pick-up and divider assembly of the original binder of three models studied was modified according to the suggestions that were given by the preliminary study. Field test showed that the modified binders were able to reduce grain losses by about 0.4-0.7 percentage points compared to those without modification.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.1
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• pp.99-106
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• 2006

Aircraft measurements have been executed for the purpose of monitoring the long range transported air pollution and estimation of air pollutant in/out-flux over the Yellow sea. Total 74 missions of measurements have been done since 1997, mainly in spring and fall. The main study domain was over $124^{\circ}$E $/sim$ $124^{\circ}$E, $35^{\circ}$N $/sim$ $37^{\circ}$N below 3,000m. In long-term trends, mixing ratios of $SO_{2}$N were around 2 ppbv expect in summer ( < 1 ppbv). NOx exhibited 24 ppbv and have no clear annual trends over the Yellow Sea. The concentrations of 03 were 51, 58, 41 ppbv in spring, summer and fall-winter, respectively. Backward trajectory was performed for three days to investigate the source regions of the air mass. Six regions were divided around Korea peninsular centering at $36^{\circ}$N, $126^{\circ}$E. I, II, III, IV and V regions represents in sequence northeast China and Siberia, Sandong peninsula and Balhae gulf, Sanghi and southern China, the south Pacific included Jeju island and the East sea included Japan. L region correspond to the airmass from Korea peninsula. Influx of $SO_{2}$N was approximately five times higher than outflux in yearly flux variation and showed a decreasing long-term trend since 1998. NOx outflux was average 0.095 ton/km/hr and three times higher than $SO_{2}$ outflux. In/out flux of 03 showed even distribution in yearly basis except 2002 (influx 5.45 ton/km/hr). The transported amounts from I, II, III regions were much higher than those from other region. In seasonal flux variation, influx levels of gas phases were the lowest in summer and the levels gradually increased from fall toward spring. As a result, transport of pollutants begins from fall and prevails in winter and spring.

• The Korean Journal of Applied Statistics
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• v.28 no.6
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• pp.1171-1180
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• 2015

Multidimensional scaling (MDS) is a graphical technique of multivariate analysis to display dissimilarities among individuals into low-dimensional space. We often have two kinds of MDS which are metric MDS and non-metric MDS. Metric MDS can be applied to quantitative data; however, we need additional information about variables because it only shows relationships among individuals. Gower (1992) proposed a method that can represent variable information using trajectories of the pseudo-points for quantitative variables on the metric MDS space. We will call his method a 'replacement method'. However, the trajectory can not be represented even though metric MDS can be applied to binary data when we apply his method to binary data. Therefore, we propose a method to represent information of binary variables using pseudo-points called a 'partition method'. The proposed method partitions pseudo-points, accounting both the rate of zeroes and ones. Our metric MDS using the proposed partition method can show the relationship between individuals and variables for binary data.

• Journal of Biosystems Engineering
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• v.13 no.3
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• pp.32-43
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• 1988

This study was attempted to investigate the pneumatic separation on separating unit of a combine harvester. The aerodynamic characteristics of threshed materials were analyzed by experiments. The air velocity distribution within the separation chamber was measured for various speeds of the winnower and suction fans to find out the operational and design conditions of the separating unit which would serve for reducing the grain loss from chaff outlet. The results of study arc summarized as follows: 1. Based on the separation curve of threshed materials analyzed, it was shown that three different kind. of materials-kernels, straw chaff, and leaf chaff were as a whole able to be separated pneumatically, regardless of varieties. However, a small amount of the separation grain loss may be expected to occur if the complete separation between kernels and straw chaff would be undertaken because some portion of their separation curve were overlapping. 2. The analysis of air velocity distribution showed that the separation chamber may be divided into two regions, the discharging and separating. The air velocity of the discharging region was 5-15 m/s and that of the separating region 2-5 m/s. 3. The air movement of the separation chamber may be a turbulence flow, being its speed became greater as it moves from the left to the right section of the separation chamber. The equi-speed line. of air flow had a steep gradient in between the discharging and the separation regions. The air velocity in the discharging region was much higher than the terminal velocity of kernels, because of which those kernels appearing in the region could be possibly exhausted as the grain loss from the chaff outlet. 4. The motion trajectory of threshed material in the separating region was dominantly affected by the winnower fan, on the other hand, its motion in the discharging region was affected by suction fan. 5. The grain loss from the chaff outlet was affected greatly by the winnower fan and the trace of kernel movement. It was observed that the optimum working speed to give minimum grain loss from chaff outlet for the combine tested should be maintained at 950~1,150 rpm for the winnower fan and 1,850 rpm for the suction fan. 6. It was shown that a large portion of grain loss from chaff outlet may occur when the kernels may bump against a portion of separation chamber wall and those kernels thus scattered into the discharging region were sucked by the suction fan. It was accordingly recommended that a new design of the wall of separation chamber so as to bump down kernels may be necessary to reduce grain loss from the chaff outlet.

• The Journal of the Korea Contents Association
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• v.12 no.3
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• pp.44-54
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• 2012

In wireless sensor networks, a moving object tracking scheme is one of core technologies for real applications such as environment monitering and enemy moving tracking in military areas. However, no works have been carried out on processing the failure of object tracking in sparse sensor networks with holes. Therefore, the energy consumption in the existing schemes significantly increases due to plenty of failures of moving object tracking. To overcome this problem, we propose a novel moving object tracking scheme based on polynomial regression prediction in sparse sensor networks. The proposed scheme activates the minimum sensor nodes by predicting the trajectory of an object based on polynomial regression analysis. Moreover, in the case of the failure of moving object tracking, it just activates only the boundary nodes of a hole for failure recovery. By doing so, the proposed scheme reduces the energy consumption and ensures the high accuracy for object tracking in the sensor network with holes. To show the superiority of our proposed scheme, we compare it with the existing scheme. Our experimental results show that our proposed scheme reduces about 47% energy consumption for object tracking over the existing scheme and achieves about 91% accuracy of object tracking even in sensor networks with holes.

• Analytical Science and Technology
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• v.27 no.4
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• pp.213-222
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• 2014

The atmospheric aerosols of $PM_{10}$ and $PM_{2.5}$ were collected at Gosan site of Jeju Island during 2012- 2013. Their ionic and elemental species were analyzed in order to examine the composition variation of the haze aerosols in accordance with the pathway of air mass. The concentrations of $nss-SO_4{^{2-}}$, $NO_3{^-}$, and $NH_4{^+}$ increased 2.1~3.7 times in coarse particle and 3.1~6.5 times in fine particle modes, respectively, showing especially high $NO_3{^-}$ concentrations in fine particles during the haze days. The concentrations of S, Zn, Pb and K increased 3.0~5.6 times in coarse particles and 3.2~7.7 times in fine particles during the haze days, on the other hand Al, Fe, and Ca concentrations were high only in coarse particles. Due to the back trajectory analysis, the concentrations of $nss-SO_4{^{2-}}$ and $NO_3{^-}$ for haze days were high when the inflow pathway of air mass was from China, especially a high increase of $NO_3{^-}$ as through the south of China. The $NO_3{^-}/nss-SO_4{^{2-}}$ concentration ratio was relatively high in coarse mode as air mass inflow from China, but in fine mode it was high as air mass passing through the Korean peninsula.