• Atmosphere
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• v.25 no.4
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• pp.659-667
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• 2015

In this study, sensitivity of inflow wind speed and turbulent Schmidt number to pollutant dispersion in an urban street canyon is investigated, by comparing CFD-simulated results to wind-tunnel results. For this, we changed systematically inflow wind speed at the street-canyon height ($1.5{\sim}10.0m\;s^{-1}$ with the increment of $0.5m\;s^{-1}$) and turbulent Schmidt number (0.2~1.3 with interval of 0.1). Also, we performed numerical experiments under the conditions that turbulent Schmidt numbers selected with the magnitude of mean kinetic energy at each grid point were assigned in the street canyon. With the increase of the inflow wind speed, the model underestimated (overestimated) pollutant concentration in the upwind (downwind) side of the street canyon because of the increase of pollutant advection. This implies that, for more realistic reproduction of pollutant dispersion in urban street canyons, large (small) turbulent Schmidt number should be assigned for week (strong) inflow condition. In the cases of selectively assigned turbulent Schmidt number, mean bias remarkably decreased (maximum 60%) compared to the cases of constant turbulent Schmidt number assigned. At week (strong) inflow wind speed, root mean square error decreases as the area where turbulent Schmidt number is selectively assigned becomes large (small).

• Journal of Astronomy and Space Sciences
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• v.32 no.3
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• pp.189-200
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• 2015

In this study, we present the results of orbit determination (OD) using satellite laser ranging (SLR) data for the Science and Technology Satellite (STSAT)-2C by a short-arc analysis. For SLR data processing, the NASA/GSFC GEODYN II software with one year (2013/04 - 2014/04) of normal point observations is used. As there is only an extremely small quantity of SLR observations of STSAT-2C and they are sparsely distribution, the selection of the arc length and the estimation intervals for the atmospheric drag coefficients and the empirical acceleration parameters was made on an arc-to-arc basis. For orbit quality assessment, the post-fit residuals of each short-arc and orbit overlaps of arcs are investigated. The OD results show that the weighted root mean square post-fit residuals of short-arcs are less than 1 cm, and the average 1-day orbit overlaps are superior to 50/600/900 m for the radial/cross-track/along-track components. These results demonstrate that OD for STSAT-2C was successfully achieved with cm-level range precision. However its orbit quality did not reach the same level due to the availability of few and sparse measurement conditions. From a mission analysis viewpoint, obtaining the results of OD for STSAT-2C is significant for generating enhanced orbit predictions for more frequent tracking.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.5
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• pp.438-444
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• 2013

This paper presents the replication of a desired vibration response by iterative learning control (ILC) system for a vibration motion replication actuator. The vibration motion replication actuator has parameter uncertainties including system nonlinearity and joint nonlinearity. Vehicle manufacturers worldwide are increasingly relying on road simulation facilities that put simulated loads and stresses on vehicles and subassemblies in order to reduce development time. Road simulation algorithm is the key point of developing road simulation system. With the rapid progress of digital signal processing technology, more complex control algorithms including iterative learning control can be utilized. In this paper, ILC algorithm was utilized to produce simultaneously the six channels of desired responses using the Stewart platform composed of six linear electro-magnetic actuators with Halbach magnet array. The convergence rate and accuracy showed reasonable results to meet the requirement. It shows that the algorithm is acceptable to replicate multi-channel vibration responses.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.128-128
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• 2010

In this study, we investigated the evolution and reduction of the surface roughness during the high-speed chemical dry thinning process of Si wafers. The direct injection of NO gas into the reactor during the supply of F radicals from NF3 remote plasmas was very effective in increasing the Si thinning rate, due to the NO-induced enhancement of the surface reaction, but resulted in the significant roughening of the thinned Si surface. However, the direct addition of Ar and N2 gas, together with NO gas, decreased the root mean square (RMS) surface roughness of the thinned Si wafer significantly. The process regime for the increasing of the thinning rate and concomitant reduction of the surface roughness was extended at higher Ar gas flow rates. In this way, Si wafer thinning rate as high as $20\;{\mu}m/min$ and very smooth surface roughness was obtained and the mechanical damage of silicon wafer was effectively removed. We also measured die fracture strength of thinned Si wafer in order to understand the effect of chemical dry thinning on removal of mechanical damage generated during mechanical grinding. The die fracture strength of the thinned Si wafers was measured using 3-point bending test and compared. The results indicated that chemical dry thinning with reduced surface roughness and removal of mechanical damage increased the die fracture strength of the thinned Si wafer.

• Journal of Hydrospace Technology
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• v.2 no.1
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• pp.1-9
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• 1996

We consider the following two questions mainly in this study. First one is how the free surface hayes affect the lift of a shallowly submerged moving body. For this matte., we reinterpret the theoretical results of Kochin(1936), and point out that the high Froude number approximation is not always on the safer side. Second one is what sort of dimensionless parameters determine the occurrence of wave breaking behind a moving submerged body. Temporarily before getting a better answer, we propose that the two-parameter-plane, namely, the plane of the Froude number and the square root of the ratio of the submerged depth and the body length, may be used for predicting the possibility of wave breaking behind the submerged body. A region in the parameter plane is put forth as that of wave breaking, and the validity of this proposal is shown by its agreement with the existing experimental data of Parkin et al(1955) and those of Duncan(1983). Finally, linear and nonlinear numerical results are compared with the existing experimental data to see in what range of the parameters the linear and nonlinear theory case predict the wave field and the pressure on the body with reasonable accuracy. However, since the experimental data, which offer both the pressure and wave elevation for a submerged moving body, are very scarce, much cannot be attained through this comparative study. Hence, it is strongly recommended to carry out well planned experiments to get such data.

• Tunnel and Underground Space
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• v.9 no.1
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• pp.12-19
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• 1999

In this study, ground vibrations of a surface blasting for golf links and a tunnel blasting for highway construction were measured to investigate the effect of blasting conditions such as total charge and distance from blasting point. In surface blasting, site factor K and n were 74.1 and -1.37, respectively, which were analyzed by means of cube root scaled distance. The more were measuring distance, the higher were absolute value of K and n. Principal frequency was in range of 5~60 Hz in surface blasting, where that of 80 percent was in range of 10~30 Hz. On the other hand it was in range of 25~98 Hz in tunnel blasting, which showed higher than of surface blasting.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.70-75
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• 1998

The comparison of Topex/Poseidon sea surface heights and Tide Gauge sea levels was studied in the South Indian Ocean after Topex/Poseidon mission of about 3 years (11- 121 cycles) from January 1993 through December 1995. The user's handbook (AVISO) for sea surface height data process was used in this study Topex/Poseidon sea suface heights ($\zeta$$^{T/P}$), satellite data at the point which is very closed to Tide Gauge station, were chosen in the same latitude of Tide Gauge station. These data were re-sampled by a linear interpolation with the interval of about 10 days, and were filtered by the gaussian filter with a 60 day-window. Tide Gauge sea levels ($\zeta$$^{Argos}$, $\zeta$$^{In-situ}$ and $\zeta$$^{Model}$), were also treated with the same method as satellite data. The main conclusions obtained from the root-mean-square and correlation coefficient were as follows: 1) to Produce Tide Gauge sea levels from bottom pressure, in-situ data of METEO-FRANCE showed very good values against to the model data of ECMWF and 2) to compare Topex/Poseidon sea surface heights of Tide Gauge sea levels, the results of the open sea areas were better than those of the coast and island areas.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.2
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• pp.89-95
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• 2010

This is the third series of article on dental occlusion and relationship to TMD and systemic symptoms. In this part of the series, it will overview the theory, treatment methods, criteria, their limitation of Chirodontics, Dental Distress Syndrome (DDS) and quadrant theorem(QT). Chirodontics has its root on Chiropractic and to maintain the 'healthy status' of TMJ with stable occlusion via dental treatment. Dental distress syndrome on the other hand believes that all the TMD has originated from reduced or collapse of posterior support and incorrect posterior vertical support had caused imbalance of the head and neck structure which eventually affect the whole body symptoms. The analysis and treatment is planned using quadrant theorem where the position of head, rotatory pivot point and occlusal plane is analyzed.

• Journal of the Korean Dietetic Association
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• v.8 no.3
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• pp.289-300
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• 2002

The purpose of this study was to investigate the intake and preference of Kimchi in middle school students. A questionnaire was used as the instrument of investigation. The subjects were 375 male and 278 female students in Masan and Changwon City. The main results of this study are as follows. Fifty-nine point seven percent of the subjects liked Kimchi, whereas 3.7% of them disliked it, and the main reason liking Kimchi was 'hot taste' of Kimchi. Korean cabbage Kimchi and cubed radish Kimchi were highly preferred. And the preferred dishes made with Kimchi were stir-fried rice with Kimchi, Kimchi stew, pan-fried Kimch, seaweed rice with Kimch, Kimch pancake, Mandu with Kimchi, pork stew with Kimch. More than 90% of the subjects had eaten 6 kinds of Kimchi : Korean cabbage Kimchi, cubed radish Kimchi, radish leaves Kimchi, radish root & leaves Kimchi, watery radish Kimchi, white Kimchi. The frequency of Kimchi intake was 55.1% of the subjects ate Kimchi in every meal time, and 21.9% ate 2 times in a day. They preferred 'well fermented' and 'freshly prepared' Kimchi, and it was significantly difference between gender, male students more liked 'freshly prepared', whereas female students more liked 'well fermented' Kimchi(p<0.01).

• Journal of Plant Biology
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• v.22 no.1_2
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• pp.21-27
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• 1979

Sandy loam plots of pH 5.5, which was created by the reclamation of highlands in Yongin county, Kyeonggi province, was selected for the present experimental study. Sugar beet was cultured in these plots by treating them with calcium hydroxide and 3 replications to maintain pH 5.5, 6.4, 6.8, 7.2, and 7.6, respectively. The growth and yield of sugar beet were investigated and the results obtained showed a great deal of boron deficiency. The growth in its early stage was favorable in high pH plots, while no significant difference was observed in sugar content, root weight and sugar production at the time of harvest in each treated plot. The tendency of sugar accumulation appeared to be identical in terms of pattern in each treated plot; i.e. sugar was accumulated until early September but declined momentarily from the middle of September and then the sugar accumulation was resumed from the middle of October. The number of individuals in boron deficiency was larger in high pH plots and the condition of such boron deficiency was also severe. The result of analysis of boron contained in plant body revealed that the boron content of individuals caused boron deficiency by water culture and that occurred in the plots was small alike. The appearance of boron deficiency is characterized by the emergence of black stripes on the surface of the basal part of petiole, severe necrosis of young leaves in the area of growing point and severe wrinkles. Therefore it is felt necessary to pay particular attention to boron deficiency in the culture of sugar beet in our country.