• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.4
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• pp.32-40
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• 2005

The purpose of this study is to investigate variation of spark plug protrusion and PDA valve on the exhaust emission in a gasoline engine. Swirl is one of the important parameters that affects the characteristics of combustion. PDA valve has been developed to satisfy requirements of sufficient swirl generation for improving the combustion and reducing of emission level. Also, especially, the variation of spark plug protrusion have an important effect to the early flame propagative process. This is largely due to the high flame speed by short of flame propagation distance. So, this is forced that injection timing, spark timing and intake air motion govern the stable combustion. As a result, using two combustion chamber, without charge of engine specification and the variable spark plug location and PDA valve could be reduced exhaust gas at a part load engine conditions(1500rpm imep 3.9bar, 2000rpm imep 3.2bar, 2400rpm imep 3.9bar).

• Journal of The Korean Astronomical Society
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• v.34 no.2
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• pp.59-66
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• 2001

In this paper, we investigate the correlation between the radial ultraviolet color distribution and the shapes of the ultraviolet isophote for elliptical galaxies (M32, NGC 1399) and spiral bulges (of M31, M81) by using their archival UIT images. For M31, M81, and NGC 1399, the radial ultraviolet color distributions show a two-component trend; as the distance from the galactic center increase the color becomes redder in the inner region while it becomes bluer in the outer region. On the other hand, the color of M32 continues to become bluer with the increasing galactocentric distance. We also find, unlike the optical/IR images, significant variations of the position angle and the ellipticity in the ultraviolet isophotes of M31, M81, and NGC 1399 through the inner regions. For M32, the variation is significant in the outer region. Since these variation implies the triaxiality of their intrinsic shapes, we suggest that the early-type galaxies and spiral bulges with a radial color gradient in ultraviolet tend to have a triaxiality. On the other hand, the shape parameter characterized by the fourth order cosine Fourier coefficient of the isophote, a(4)/a, indicates that the systematic deviations of the ultraviolet isophotes of the four galaxies are smaller than $\~0.2\%$ in units of the semi-major axis. The latter result implies that the ultraviolet isophotes of the galaxies have a pure elliptical shape rather than the boxy or disky shapes. Therefore, there is no clear evidence of correlation between the radial ultra-violet color gradient and the boxy/disky shapes of isophotes.

• Journal of Korean Society for Geospatial Information Science
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• v.10 no.5 s.23
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• pp.75-80
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• 2002

Depending upon geographical features and surrounding errors in the survey field, inaccurate positioning is inevitable in a kinematic DGPs survey. Therefore, a data inaccuracy detection algorithm and an interpolation algorithm are essential to meet the requirement of a digital map. In this study, GPS characteristics are taken into account to develop the data inaccuracy detection algorithm. Then, the data interpolation algothim is obtained, based on the feature type of the survey. A digital map for 20km of a rural highway is produced by the kinematic DGPS survey and the features of interests are lines associated with the road. Since the vertical variation of GPS data is relatively higher, the trimmed mean of vertical variation is used as criteria of the inaccuracy detection. Four cases of 0.5%, 1%, 2.5% and 5% trimmings have been experimented. Criteria of four cases are 69cm, 65cm, 61cm and 42cm, respectively. For the feature of a curved line, cublic spine interpolation is used to correct the inaccurate data. When the feature is more or less a straight line, the interpolation has been done by a linear polynomial. Difference between the actual distance and the interpolated distance are few centimeters in RMS.

• International Journal of Korean Welding Society
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• v.2 no.2
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• pp.51-56
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• 2002

The weld seam tracking system for arc welding process uses various kinds of sensors such as arc sensor, vision sensor, laser displacement sensor and so on. Among the variety of sensors available, electro-magnetic sensor is one of the most useful methods especially in sheet metal butt-joint arc welding, primarily because it is hardly affected by the intense arc light and fume generated during the welding process, and also by the surface condition of weldments. In this study, a dual-electromagnetic sensor, which utilizes the induced current variation in the sensing coil due to the eddy current variation of the metal near the sensor, was developed for arc welding of sheet metal I-butt joints. The dual-electromagnetic sensor thus detects the offset displacement of weld line from the center of sensor head even though there's no clearance in the joint. A set of design variables of the sensor was determined far the maximum sensing capability through the repeated experiments. Seam tracking is performed by correcting the position of sensor to the amount of offset displacement every sampling period. From the experimental results, the developed sensor showed the excellent capability of weld seam detection when the sensor to workpiece distance is near less than 5 ㎜, and it was revealed that the system has excellent seam tracking ability for the I-butt joint of sheet metal.

• Development and Reproduction
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• v.19 no.4
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• pp.259-264
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• 2015

Genomic DNA samples isolated from geographical purplish Washington clam (Saxidomus purpuratus) were obtained from three different regions in the Korean Peninsula: Geoje (Geoje population; GJP), Gunsan (Gunsan population; GSP) and a site of North Korea (North Korea population; NKP). The seven primers generated the total 369 loci that can be scored from the GSP clam population. 356 fragments were generated from the NKP clam population. The complexity of the banding patterns varies dramatically between the primers and three localities. In this study, 319 loci were identified in the purplish Washington clam from Geoje and 369 in the clam population from Gunsan: 221 specific loci (69.3%) in the GJP clam population and 300 (81.3%) in the GSP population. These results demonstrate that the primer detected a large quantity of specific fragments, suggesting that the genetic variation in the GSP is higher than in the GJP population. In particular, the BION-28 primer gave DNA profiles with more fragments than the other six primers in the NKP population. The oligonucleotides primer BION-75 produced 21 unique loci to each population, which were ascertaining each population, approximately 250 bp, 300 bp and 400 bp, in the GJP population. Outstandingly, the primer BION-50 detected 21 shared loci by the three populations, major and/or minor fragments of sizes 150 bp, which were matching in all samples. With regard to average bandsharing value (BS) results, individuals from GJP population (0.743) displayed higher bandsharing values than did individuals from GSP population (0.606). In the present study, the dendrogram gained by the seven oligonucleotides primers indicates three genetic clusters: cluster 1 (GEOJE 01 ~ GEOJE 07), cluster 2 (GUNSAN 08 ~ GUNSAN 14), cluster 3 (N.KOREA 15 ~ N.KOREA 21). Among the twenty one clams, the shortest genetic distance that revealed significant molecular differences was between individuals 08 and 09 from the NKP population (genetic distance = 0.073), while the longest genetic distance among the twenty-one individuals that demonstrated significant molecular differences was between individuals GEOJE no. 03 and GUNSAN no. 09 (genetic distance = 0.669). Comparatively, individuals of GJP population were properly closely related to that of NKP population, as revealed in the hierarchical dendrogram of genetic distances. In due course, PCR analysis has revealed the significant genetic distance among three purplish Washington clam populations. PCR fragments discovered in this study could be valuable as a DNA marker of the three geographical clam populations to distinguish.

• Development and Reproduction
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• v.15 no.4
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• pp.359-364
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• 2011

The seven selected primers OPA-02, OPA-04, OPA-18, OPD-07, OPD-08, OPD-15 and OPD-16 were used to generate unique shared loci to each species and shared loci by the two species. The hierarchical dendrogram indicates three main branches: cluster 1 (RORETZI 01~RORETZI 11) and cluster 2 (HILGENDORF 12~HILGENDORF 22) from two geographic populations of ascidians, Halocynthia roretzi and H. hilgendorfi. The shortest genetic distance displaying significant molecular difference was between individuals' HILGENDORF no. 14~HILGENDORF no. 19 (genetic distance =0.008). Ultimately, individual no. 02 of the RORETZI ascidian was most distantly related to HILGENDORF no. 21 (genetic distance=0.781). These results demonstrate that the H. roretzi population is genetically different from the H. hilgendorfi population. From what has been said above, the potential of PCR analysis to identify diagnostic markers for the identification of two ascidian populations has been demonstrated. Generally speaking, using a variety of decamer primers, this PCR method has been applied to identify specific markers particular to line, species and geographical population, as well as genetic diversity/polymorphism in diverse species of organisms.

• Journal of Environmental Impact Assessment
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• v.19 no.3
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• pp.223-230
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• 2010

Trajectory dispersion models are used for the dispersion calculations in air quality assessments, Yellow-sand modeling, environmental planning and the emergency response. Meso-scale forcing and coastal circulations are calculated by trajectory model in the East Asia region. In this study the meteorological fields (GDAS and MM5) coupled to the trajectory model (HY-SPLIT) are applied to simulate the transport and the dispersion. Seoul is selected as a starting point of the HY-SPLIT. The sensitivity studies are performed by conducting an ensemble of simulations using the GDAS and the MM5 model for the same dispersion cases. The results in this study show a significant difference depending on the resolution of meteorological models. Additionally, in most cases of the compared tionally,results from MM5 and GDAS, the absolute and relative distance, shows significant difference and the difference increased with the increasing distance of HY-SPLIT. Therefore, for the case of small domai for twi d field distefbution over complex terrai, should be used only high model temporal or spatial resolution to improve the HY-SPLIT model results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3208-3216
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• 1993

Heat transfer characteristics of the laminar oscillating flow in a circular pipe have been studied under the condition that the wall temperature of the pipe is distributed sinusoidally with the axial direction. The axial velocity was assumed to be uniform in radial direction and the temperature field was analyzed by means of the perturbation method. The results show that the difference between wall and section-time-averaged fluid temperature increases as the oscillating frequency increases and eventually converges to a constant value which is determined by the ratio of swept distance to the characteristic length of wall temperature distribution. Also it is shown that the dominant variable in the heat transfer process when swept distance ratio is greater than 1 is not thermal Womersley number(F) but thermal Womersley number multiplied by the square root of swept distance ratio. The variation of the time-averaged Nusselt number is obtained as a function of F. The results indicate that Nusselt number is proportional to $F_{\epsilon}^{1/2}$ when both of F and .epsilon. are much greater than 1.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.4
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• pp.73-80
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• 2013

Breakdown characteristics of air in the vertical arrangement of line conductor and plane electrode in case of combustion flame on the plane electrode are examined by the application of AC. and DC voltages to the gap. In order to investigate the effect of paraffin flame on the breakdown characteristics of air, flashover voltages are measured according to the variation of the gap length and the horizontal distance between the flame and the line conductor. As the result of the experiment, flashover voltages are substantially lowered down to 29.8% in case of the AC voltage, and 16.1% in case of the negative DC voltage, when in the presence of the flame. from 100% when in the absence of flame. Flashover voltages of air in the range of smaller than 3㎝ at the horizontal distance are increased in the proportion of the gap length and the horizontal distance in case of both AC and negative DC voltages. But before the flashover occurs, the flame is extinguished by such corona wind that is produced from the line conductor when the gap length and the horizontal distance reach to a certain degree. The effect of relative air density and the phenomenon of thermal ionization are analysed as the reduction factors of flashover voltages, due to high temperature of the flame.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.5
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• pp.985-996
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• 2000

In the coastal zone, to draw up short and medium range weather forecasts, mesoscale pluviogenic systems coming from the sea have to be observed in real time. These observations use remote sensing. However, satellite remote sensing is not sufficient to describe pluviogenic systems; reference to radar long distance observations is indispensable. This paper deals with the corrections, which must be made to long distance radar data if the rainfall field is to be both accurately and quantitatively defined. The error due to vertical variation in the reflectivity factor can be corrected from estimation of the mean profiles or by a climatic adjustment method. Atten-uation in the propagation can be corrected by an iterative polarimetric method. These various correc-tions permit the distance validity limits of radar data to be extended.