• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.22 no.9
• /
• pp.1217-1228
• /
• 1998

In order to elucidate the operational characteristics of rotating heat pipes, the internal flow patterns and heat transfer performance are investigated. Flow patterns and its transition are studied with various rotational speeds by visualizing flows established inside a rotating tube. To verify those results of analysis, 2 heat pipes of the same geometries but fill charge rates of 7, 30% were manufactured and submitted to operating tests. Comparison of experimental results on heat transfer rate show a fairly good agreement with the analytical results. The analysis reveals that the optimum charge ratio is ranged in 4~7% depending on the quantity of thermal loads. but the heat pipe with 7% of fill charge ratio reached dry-out limitation at heat flux of $q^{{\prime}{\prime}}=6.2kW/m^2$ lower than that of analytic results. Transition of flow regime was well related to the correlation by Semena & Khmelev on transient centrifugal Froude Number Frc. But hysteresis phenomenon was observed in transition of flow regime, when the rotational speed was stepwisely changed in the way to undergo 1 cycle.

• Journal of Biomedical Engineering Research
• /
• v.36 no.3
• /
• pp.61-68
• /
• 2015

In this paper, we studied the effects of intersection angles of the flow-foucusing type droplet generation device inlet channel on droplet diameter using numerical simulation modeling. We modeled different intersection angles with a fixed continuous channel width, dispersed channels width, orifices width, and expansion channels width. Numerical simulations were performed using COMSOL Multiphysics$^{(R)}$ to solve the incompressible Navier-Stokes equations for a two-phase flow in various flow-focusing geometries. Modeling results showed that an increase of the intersection angle causes an increase in the modification of the dispersed flow rate ($v^{\prime}{_d}$), and the increase of the modification of the continuous flow rate ($v^{\prime}{_c}$) obstructs the dispersed phase fluid flow, thereby reducing the droplet diameter. However, the droplet diameter did not decrease, even when the intersection angle increased. The droplet diameter decreased when the intersection angle was less than $90^{\circ}$, increased at an intersection angle of $90^{\circ}$, and decreased when the intersection angle was more than $90^{\circ}$. Furthermore, when the intermediate energy deceased, there was a decrease in the droplet diameter when the intersection angle increased. Therefore, variations in the droplet diameter can be used to change the intersection angle and fluid flow rate.

• Journal of the Korea Furniture Society
• /
• v.28 no.3
• /
• pp.248-258
• /
• 2017

A study was carried out to observe the 1% aqueous safranine solution flow speed in longitudinal and radial directions of softwood Thuja orientalis L., diffuse-porous wood Gmelina arborea Roxb., and ring-porous wood Phellodendron amurense Rupr., Longitudinal flow was considered from bottom to top while the radial flow was considered from bark to pith directions. In radial direction, ray cells and in longitudinal direction tracheids, vessel and wood fiber were considered for the measurement of liquid penetration speed at less than 12% moisture contents(MC). The variation of penetration speed for different species was observed and the reasons behind for this variation were explored. The highest radial penetration depth was found in ray parenchyma of T. orientalis but the lowest one was found in ray parenchyma of P. amurense. The average liquid penetration depth in longitudinal trachied of T. orientalis was found the highest among all the other cells. The penetration depth in fiber of G. arborea was found the lowest among the other longitudinal cells. It was found that cell dimension and also meniscus angle of safranine solution with cell walls were the prime factors for the variation of liquid flow speed in wood. Vessel was found to facilitate prime role in longitudinal penetration for hardwood species. The penetration depth in vessel of G. arborea was found highest among all vessels. Anatomical features like ray parenchyma cell length and diameter, end-wall pits number were found also responsible fluid flow differences. Initially liquid penetration speed was high and the nit gradually decreased in an uneven rate. Liquid flow was captured via video and the penetration depths in those cells were measured. It was found that even in presence of abundant rays in hardwood species, penetration depth of liquid in radial direction of softwood species was found high. Herein the ray length, lumen area, end wall pit diameter determined the radial permeability. On the other hand, vessel and fiber structure affected the longitudinal flow of liquids. Following a go-stop-go cycle, the penetration speed of a liquid decreased over time.

• Journal of Korea Water Resources Association
• /
• v.47 no.6
• /
• pp.523-536
• /
• 2014

A water supply reliability is mainly influenced by water demand, reservoir storage, and inflow change caused from drought. The water supply reliability can vary depending on the method of dam operation. In Korea, the deficit-supply method which complements water deficit as water shortage occurs in downstream areas has been used for the national water resources master plan using K-WEAP, but the prime flow method, an alternative approach, would show different results of water supply reliability in comparison to the deficit-supply method. The objective of this research is to compare and analyze differences in water supply reliability according to dam operation methods. These results can be used to re-evaluate water supply reliability of dam in a circumstance considering steady dam release for instreamflow in downstream and hydroelectric power generation.

• The Journal of Korean Academic Society of Nursing Education
• /
• v.25 no.4
• /
• pp.393-404
• /
• 2019

Purpose: This study aims to investigate the influence of personality type, self-leadership, and positive psychological capital on the flow of learning of nursing students. Methods: The sample consisted of 179 nursing students. Data were analyzed using frequency, percentage, mean, standard deviation, t-test, ANOVA, $Scheff{\acute{e}}^{\prime}s$ test, Pearson's correlation coefficient analysis, and Hierarchical multiple regression. Results: Upon analysis, the relative influence of the variables that can improve learning flow, the influencing variables, were identified as self-leadership and self-efficacy. Conclusion: To increase the learning flow, supportive measures and strategies that increase positive psychological capital should be developed, successful cases of self-leadership be shared, and be incorporated into a culture that promotes learning flow. And to promote the learning flow, it needs political and environmental improvement, and institutional support of at the college level.

• Journal of Life Science
• /
• v.23 no.6
• /
• pp.728-735
• /
• 2013

Plantago asiatica (Plantaginaceae) is a wind-pollinated plant that grows mainly on fields in East Asia. Starch gel electrophoresis was used to investigate the allozyme diversity and population structure of 18 populations of this species. Although the plantain populations were isolated and patchily distributed, they maintained a high level of genetic diversity; the average percentage of polymorphic loci was 57.1%, the mean number of alleles per locus was 2.07, and the average heterozygosity for 18 populations was 0.201. The combination of a predominant wind-pollinated, mix-mating reproduction, large population sizes, high gene flow between subpopulations, and a propensity for high fecundity may explain the high level of genetic diversity within populations. A direct gradient in overall genetic diversity is associated with latitude. Genetic diversity of P. asiatica is markedly decreased from $35^{\circ}3^{\prime}$ to high latitude and decreased from $35^{\circ}3^{\prime}N$ to low latitude, whereas there does not show a longitudinal gradient in genetic diversity.

• Steel and Composite Structures
• /
• v.22 no.6
• /
• pp.1261-1280
• /
• 2016

We study chaotic motion in a nonlinear laminated composite plate under subsonic fluid flow and a simultaneous external load in this paper. We derive equations of motion of the plate using the von-$K{\acute{a}}rm{\acute{a}}n^{\prime}s$ hypothesis and the Hamilton's principle. Galerkin's approach is adopted as the solution method. We then conduct a divergence analysis to obtain critical velocities of the transient flow. Melnikov's integral approach is used to find the critical parameters in which chaos takes place. Effects of different parameters including the aspect ratio, plate material and the ply angle in laminates on the critical flow speed are investigated. In a parametric study, we show that how the linear and nonlinear stiffness of the plate and the load frequency and amplitude would influence the chaotic behavior of the plate.

• Proceedings of the KSME Conference
• /
• 2001.11b
• /
• pp.604-609
• /
• 2001

This numerical analysis uses the lifting surface method and frequency-domain panel method based on the linear compressible aerodynamic theory. Increased knowledge of flow conditions within mixed-flow fan should indicates means of improving performance of these turbomachines. Thus, only an approximate solution is obtained whose prime intent is to recognize the most significant characteristics of the "ideal" geometry. For a given set of operating condition, the flow conditions within mixed-flow fan depend on the geometry of the machine (three-dimensional flow effects) and on the properties of the fluid. But most treatments of the problem have been concerned with the two-dimensional flow effects for incompressible, non-viscous fluids. Interest in the field of mixed-flow fan resulted in the undertaking of a program to develop reliable design procedures that would avoid the need for lengthy development work.

• IE interfaces
• /
• v.15 no.1
• /
• pp.55-63
• /
• 2002

This paper utilizes the FIDO methodology (Function, Information, Dynamic, Organization modeling) which is an enterprise modeling tool that can describe inter-organizational interaction (specifically between prime and sub contractors in this experiment). FIDO follows the standard IDEFO rules in order to demonstrate how a cascading information flow can evolve from a customer to a prime to a subcontractor in a concurrent manner, in a supply chain environment. Background on these processes is presented, followed with the newly derived process and methodology. This is presented in a supply chain management context, and results from an actual experiment at Motorola utilizing subcontractors that supply custom machine parts is presented and reviewed.

• Journal of Oral Medicine and Pain
• /
• v.43 no.4
• /
• pp.99-111
• /
• 2018

$Sj{\ddot{o}}gren^{\prime}s$ syndrome (SjS) is a common autoimmune disorder characterized by lymphocytic infiltration in the salivary and lacrimal glands, resulting in severe dry mouth or eyes. As a result, most of SjS patients suffer from oral dryness and can visit the department of oral medicine with or without diagnosis of SjS. Therefore, oral medicine specialists should know clues, which may indicate the diagnosis of SjS from the clinical and laboratory investigations. By the recent SjS criteria, SjS can be diagnosed by focus score, ocular staining, Schirmer's test, unstimulated whole saliva flow rate, and anti-SSA/Ro antibodies. The aim of this article is to review the diagnostic criteria, clinical investigation, and basic aspect related to SjS and to make oral medicine specialists play an important role in the detection of emerging SjS.