• Advances in concrete construction
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• v.10 no.6
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• pp.499-507
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• 2020

In current study, utilizing the Kelvin's theory with polynomial, exponential and trigonometric volume fraction laws for functionally graded cylindrical shell vibrations. Effects of different parameters for ratios of length- and height-to-radius and angular speed versus fundamental natural frequencies been determined for two categories of cylindrical shells with clamped-free edge condition. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing length-to-radius ratio. Moreover, on increasing the rotating speed, the backward frequencies increases and forward frequencies decreases. The frequencies are same when the cylinder is stationary. The frequencies increases and decreases on changing the constituent materials. The frequency results are verified with the earlier literature for the applicability of present model.

• Korean Journal of Plant Taxonomy
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• v.31 no.4
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• pp.359-373
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• 2001

One of Korean Typha species has been used two scientific names, T. angustifolia L. and T. angustata Bory et Chaubard without taxonomic examinations. Typha angustifolia has a longer females flowers than bracteoles and equal length of bracteoles and hairs in female flowers whereas T. angustata has equal length of female flowers and bracteoles and longer bracteloes than hairs in female flowers. In this study, the pattern of morphological variation of T. angustifolia in Korea is examined using numerical analysis to determine their taxonomical identities. Univariate analysis using morphological characters such as female flower length/bracteole length and bracteole lengh/hair length reveals that Korean T. angustifolia is composed of one group. The result of principal components analysis shows that Korean T. angustifolia is closely related to T. angustifolia distributed in Japan, Russia, and USA. Therefore, T. angustifolia L. (in Korea) is suggested as a legitimate scientific name.

• Korean Journal of Heritage: History & Science
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• v.56 no.1
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• pp.132-140
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• 2023

In this study, a total of 21 parts of the head, carapace, and plastron of 21 tortoises were examined to investigate the characteristics of male and female sexual dimorphism of the Reeve's turtle (Mauremys reevesii), a natural monument in Korea. The ratio values of a total of 19 areas were derived from Head Length (HL) and Carapace Length (CL). As a result of comparing the ratio values, it was found that male tortoises had larger head length, head width, and head height than females compared to the size of the carapace. Since females grow eggs inside the body through internal fertilization after mating, female carapaces are judged to be larger than males overall. As a result of statistical analysis of the ratio values of the measured values, Plastron Length (PL), Bridge Length (BL), Gular Length (GL), Interhumeral Length (IH), Interanal Length (IAN), Femoral-Anal seam (FA) and Head Height (HH) showed statistically significant differences. Statistically significant in the part of the plastron, it is judged that the tortoise acts directly on each deck of the plastron as it grows. In addition, the head size of male tortoises was smaller than that of females, but it was found to be larger in proportion. It is considered that the tortoise has a rather large head compared to the body due to the male's habit of shaking his head and courtship behavior before mating. This study, we were able to identify the characteristics of sexual dimorphism in Reeve's turtle. However, since most of them were rescued, it was not possible to accurately determine habitat and age. In the future, if additional studies are conducted on individuals with clear habitats and ages, it is expected that the characteristics of the physical differences that develop as they grow can be identified.

• Journal of Energy Engineering
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• v.24 no.1
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• pp.97-103
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• 2015

Natural convection heat transfer rates in vertical pipes were measured varying the diameter, length, and roughness of vertical cylinder. To achieve high Rayleigh number with relatively small test rig, mass transfer experiments instead of heat transfer were performed based on the analogy. Prandtl number was 2,014. The length of vertical cylinder was 0.1m, 0.3m, and 0.5m, which correspond to GrL $4.2{\times}10^7$, $1.1{\times}10^9$, and $5.5{\times}10^9$. To each length of vertical cylinder, the heat transfer rates were measured varying the iameter 0.005m, 0.01m, and 0.03m. The heat transfer rate for a short length pipe(0.1m) agreed with the prediction from Le Fevre correlation developed for a vertical plate for all diameter. The heat transfer rate decreases as the diameter and the length of the pipe increases. The heat transfer rate inside of vertical cylinder is affected by roughness only for a laminar flow regime.

• The Journal of the Acoustical Society of Korea
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• v.9 no.2
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• pp.14-24
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• 1990

A Study is made on shrink fit shaft in which its part is modelled and spring stiffness per unit length is estimated, then obtained transfer matrix. Transfer matrix of shaft is found by Myklestad's method and natural frequency is found by shrink fit tolerance on shrink fit shaft, too. In order to verify effectiveness of shrink fit effect, hollow shaft of the same size is compared with shrink fit shaft which will verified on experiment. As a result of this study, the more shrink fit tolerance increases, the more spring stiffness per unit length increases. It is obvious from the above results that shrink fit shaft due to shrink fit tolerances decreases natural frequency.

• Korean Journal of Soil Science and Fertilizer
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• v.50 no.3
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• pp.179-186
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• 2017

This study was conducted to identify characteristics of domestic pine forest soils and to elucidate major soil influencing factors for natural regeneration. We analyzed the physico-chemical characteristics of the soil samples collected from 23 pine forests and confirmed the similar results with the forest soil characteristics. Soil pH, organic matter content, total nitrogen, exchangeable Ca, silt content, and exchangeable Al were selected as the major soil factors among the exposed soils through 10 days of pine seedlings exposure and cultivation experiments and statistical analysis. Multiple regression analysis showed that soil pH had a positive effect on specific root length (SRL) of red pine seedlings and exchangeable Al was a significant factor affecting negative change in SRL. Taken together, the reduction of exchangeable Al by soil pH adjustment would be helpful for natural regeneration by restoring the forest and improving the fine root and root integrity of pine seedlings. Therefore, soil pH and exchangeable Al could be recommended as a major soil factor to be carefully considered in the monitoring and management of soil in pine forests that need to be renewed in the future.

• Journal of Environmental Science International
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• v.3 no.1
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• pp.57-64
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• 1994

On the basis of the principle of Bratch's electronegativity equalization, we calculated group partial charges and group electronegativities for nonionic surfactants with Pauling's elecoonegativity parameters by using numerical calculation method. From calculated outputs we have investigated structural stability of micelle, characteristics of hydrophilic and hydrophobic groups, and relation between CMC(Critical Micelle Concentraion) and group partial charge and group electronegativity of hydrophilic and hydrophobic groups for nonionic surfactants. We have known that CMC by micelle formation depends upon group partial charge and group electronegativity of hydrophilic and hydrophobic groups for surfactants. Also, the structural stability of micelle in H2O solution is related to the electric double layer by the hydrophilic group of nonionic surfactants with H atoms in water CMC is diminished by the decrease of repeating units in hydrophilic group at constant hydrophobic group and is diminished by the increments of alkyl chains in hydrophobic group at constant hydrophilic group for nonionic surfactants. In conclusion, CMC is diminished because there is no electrostatic repulsion and is diminished of Debye length by the increments of partial charge of hydrophobic group.

• Structural Engineering and Mechanics
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• v.56 no.4
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• pp.589-603
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• 2015

The mixed-mode stress intensity factors of 2-D angled cracks are evaluated by Petrov-Galerkin natural element (PG-NE) method in which Voronoi polygon-based Laplace interpolation functions and CS-FE basis functions are used for the trial and test functions respectively. The interaction integral is implemented in a frame of PG-NE method in which the weighting function defined over a crack-tip integral domain is interpolated by Laplace interpolation functions. Two Cartesian coordinate systems are employed and the displacement, strains and stresses which are solved in the grid-oriented coordinate system are transformed to the other coordinate system aligned to the angled crack. The present method is validated through the numerical experiments with the angled edge and center cracks, and the numerical accuracy is examined with respect to the grid density, crack length and angle. Also, the stress intensity factors obtained by the present method are compared with other numerical methods and the exact solution. It is observed from the numerical results that the present method successfully and accurately evaluates the mixed-mode stress intensity factors of 2-D angled cracks for various crack lengths and crack angles.

• Journal of computational fluids engineering
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• v.18 no.2
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• pp.35-40
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• 2013

Natural convection of air with Pr=0.7 between two horizontal plates with small magnitude non-uniform temperature distribution[${\in}{\Delta}Tsin({\kappa}X/H)$, H : gap width, X : horizontal coordinate] in the lower plate is numerically(${\in}=0.01$) investigated. In the conduction-dominated regime with $Ra{\leq}1700$, two upright cells are formed over one wave length($2{\pi}/{\kappa}$). For small wave number, the flow becomes unstable with increase of Rayleigh number, and multicellular convection occurs above a critical Rayleigh number. The flow patterns are classified by the number of eddies over one wave length. When ${\kappa}=1$, a transition of $2{\rightarrow}4{\rightarrow}6$ eddy flow occurs with increase of Rayleigh number, and no hysteresis phenomenon is observed. Dual and triple solutions are found for ${\kappa}=1$, and transitions of $10{\rightarrow}8$, $8{\rightarrow}6$, $6{\rightarrow}4{\rightarrow}2$ eddy flow occur with decrease of Rayleigh number.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.673-682
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• 1997

The main purpose of this paper is to investigate the effects of rotatory inertia and shear deformation on the natural frequencies of arches with variable curvature. The differential equations are derived for the in-plane free vibration of linearly elastic arches of uniform stiffness and constant mass per unit length. The governing equations are solved numerically for parabolic, circular and elliptic geometries with hinged-hinged, hinged-clamped and clamped-clamped end constraints. For each cases, the four lowest frequency parameters are presented as functions of the two dimensionless system parameters; the arch rise to span length ratio, and the slenderness ratio.