• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1153-1160
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• 2010

A circular plate is the main part of a circular saw blade, which is widely used in industrial cutting tools. In experiments using a circular saw containing slots, we observed that a number of natural frequencies are simultaneously emerged in specific frequency regions. The interesting phenomenon is called the frequency convergence. Effects of design parameters such as the number, the length and the width of slots, on the frequency-convergence phenomenon are analyzed by FEM simulations using ALGOR. The frequency-convergence phenomenon will be intensified when the number, length and width of slots increase.

• Korean Journal of Plant Resources
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• v.11 no.2
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• pp.210-216
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• 1998

Taxonomic studies in external morphology, principal component analysis and cluster analysis were conducted to understand the intraspecific relationship among three habitats (Jirisan, Odaesan and Ulleungdo) of allium voctorialis var. platyphyllum. External morphology such as bulb color, leaf blade length and width, petiole length, total leaf length, peduncle length, perianth lobe length and width, length of anther and filament were useful characters for identification of poplations in three habitats. The results obtained based on the principal component (Pc) analysis of treated 72 OTUs(included outgroup) were divided into three groups by the PC 1 ,2,3 and the sums of contributions for the total variance were 84.1%(PC1 51.0%, PC2 24.9% and PC3 8.2%, respectively). In cluster analysis by the UPGMA and Ward's methods , there was similarities in the compostion of clustered taxa, and only Ulleungdo population was distinctly identified from population of other two habitats.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.100-104
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• 2019

We have investigated the feasibility of fabricating fine stripes using needle coating for potential applications in solution-processed organic light-emitting diodes (OLEDs). To this end, we have employed an aqueous poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) solution that has been widely used as a hole injection layer (HIL) of OLEDs and performed needle coatings by varying the process parameters such as the coating gap and coating speed. As expected, the stripe width is reduced with increasing coating speed. However, the central thickness of the stripe is rather increased as the coating speed increases, which is different from other coating processes such as slot-die and blade coatings. It is due to the fact that the meniscus formed between the needle tip and the substrate varies depending sensitively on the coating speed. It is also found that the stripe width and thickness are reduced with increasing coating gap. To demonstrate its applicability to OLEDs, we have fabricated a red OLED stripe and obtained light emission with the width of about 90㎛.

• Korean Journal of Plant Resources
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• v.24 no.5
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• pp.540-548
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• 2011

Characteristics of leaf morphology was examined in 11 natural populations of Acer pictum subsp. mono (Maxim.) Ohashi in Korea. Nested Anova showed that there were statistically significant differences among populations as well as among individuals within populations in all 14 quantitative characters. In all the leaf characters, variance components among individuals within populations were higher than those among populations. Some morphological characters such as the ration of Blade length to Petiole length (0.90), Uower lobe width (0.85), Blade length (0.83), and Middle lobe width (0.83) showed the relative high differences in the values of differentiation (Dij) among populations. Of the ten populations, Gwangyang (1.36) and Cheongyang (1.30) were highly differentiated based on the total mean Dij of fourteen morphological characters, while Ulju (0.30) and Jeongseon (0.44) were scarcely differentiated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.10
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• pp.645-651
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• 2016

Effects of pressure-side winglet width on the tip leakage flow and aerodynamic loss downstream of a turbine blade with a pressure-side squealer rim have been investigated for the tip gap-to-span ratio of h/s = 1.36%. The pressure-side squealer has a fixed height-to-span ratio of $h_p/s=3.75%$ and the pressure-side winglet, which is installed at an elevation of tip surface, has width-to-pitch ratios of w/p = 2.64%, 5.28%, 7.92% and 10.55%. The results show that with increasing w/p, aerodynamic loss in the passage vortex region decreases, whereas that in the leakage flow region increases. As a result, the mass-averaged loss coefficient all over the measurement plane tends to decrease minutely with the increment of w/p. It is concluded that the pressure-side winglet for the pressure-side squealer tip can hardly contribute to the tip-leakge loss reduction.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.707-718
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• 2019

Ecklonia cava Kjellman, which has recently gained popularity due to the spread of farming techniques, is expected to be developed in various varieties in the future. There exist increased needs for research on the basis of natural populations and inter-regional morphological variations. We compared the morphology of the aquaculture and natural populations from 16 coastal areas in Korea. The 18 traits found suitable for distinguishing varieties were selected from 14 measurement traits and 4 ratios related to the main morphology and characteristics of primary blade, secondary blade, and stipe. In the cluster analysis, Janggil (E4) and Sorok (S7) showed significant differences from those of the same coastal region. Two groups, including Suyou (Q6, Q8, and Q10) which was the second year of farming, of the rest of the populations from East sea and southern coast were distinguished. Three populations of Jeju were divided into a regional group. In the principal component analysis (PCA), a large number of populations from East sea and Southern coast appeared in the center with aquaculture populations. PC1 and PC2 associated with traits of secondary blade index, stipe length and diameter, stipe length/primary blade length, primary blade length and width, secondary blade number, secondary blade length and width, divided E4, S7 and populations of Jeju region. As a result, the 18 characters of this study were found to be useful as criteria for discrimination of populations with significant differences in each coastal region, and these populations were expected to be candidates for new varieties.

• Journal of Korean Society of Forest Science
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• v.95 no.3
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• pp.261-267
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• 2006

A nursery trial comprising 109 progenies of 5 populations of Cornus kousa was analysed using multivariate analysis of 12 quantitative traits (growth and leaf form). The aim of this study was to examine geographic variation of the species based on the single, existing nursery trial to support a genetic resource conservation plan of Cornus kousa in Korea. Nested Anova showed that there were statistically significant differences among populations as well as among families within populations in all 12 quantitative traits. In 10 of 12 traits, variance components among families within populations were higher than those among populations. Cluster analysis using complete linkage method showed three groups to Euclidean distance 0.8. Among principal components, primary 2 principal components appeared to be major variables because of the loading contribution of 91.9%. The first contribution component was maximum width, vein number, blade length/petiole length and upper 1/3 width lower 1/3 width; the second one was height, diameter at root collar, blade length, upper 1/3 width, petiole length and petiole length/vein number, respectively. But all characters showed no significant difference with the pattern of geographic distribution.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.737-741
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• 2003

The wind power system is spotlighted as one of the no-pollution power generation systems. The system uses winds as power source that are rotated the blade and the rotating power from blade generate the electricity power. Gearbox needs to transfer the wind powers that have the high-torque-low-speed characteristics to generator that have the low-torque-high-speed characteristics. Because the wind power system generally locates the remote place like seaside or mountainside and the gearbox installs on the limited and high placed space, the gearbox of the wind power system is required the optimal space design and high reliability. In this paper, the structure of the gearbox is proposed to achieve the optimal space and efficiency by compounding the planetary gear train that has the high power density and parallel type gear train that has the long service life. The design parameters that are affected the service life are studied. The gear ratio and face width are investigated as an affected parameter for design sensitivity of service life.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1726-1731
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• 2004

This paper presents the response surface optimization method using three-dimensional Navier-Stokes analysis to optimize the shape of a forward-curved blades centrifugal fan. For numerical analysis, Reynolds-averaged Navier-Stokes equations with $k-{\varepsilon}$ turbulence model are discretized with finite volume approximations. In order to reduce huge computing time due to a large number of blades in forward-curved blades centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models. Three geometric variables, i.e., location of cut off, radius of cut off, and width of impeller, and one operating variable, i.e., flow rate, were selected as design variables. As a main result of the optimization, the efficiency was successfully improved. And, optimum design flow rate was found by using flow rate as one of design variables. It was found that the optimization process provides reliable design of this kind of fans with reasonable computing time.

• The KSFM Journal of Fluid Machinery
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• v.11 no.3
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• pp.30-35
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• 2008

The purpose of this study is to examine the effect of nozzle shapes on the performance and internal flow characteristics of a cross-flow type hydro turbine for wave power generation. The performance of the turbine is calculated with the variation of rotational speed for 4 types of the nozzle shape using a commercial CFD code. The results show that nozzle shape should be designed considering available head of the turbine. Best efficiencies of the turbine by 4 types of the nozzle shape do not change largely but overall performances varies mainly by the nozzle width. The output power of the cross-flow type hydro turbine changes considerably by the nozzle shape and a partial region of stage 2 in the runner blade passage produces maximum regional output power in comparison with the other runner blade passage areas.