• Design & Manufacturing
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• v.13 no.1
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• pp.42-47
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• 2019

Nucleate boiling heat transfer is one of the most important phenomenon in the various industries. Especially, critical heat flux (CHF) refers to the upper limit of the pool boiling heat transfer region. Therefore, many researchers have found that CHF can be significantly increased by adding very small amounts of nanoparticles. In this study, the CHF and heat transfer coefficient were tested under the pool boiling state using copper and multi wall carbon nanotube nanoparticles. The results showed that two different types of nanoparticles deposited on the surface of two specimens made of the same material increased the heat flux in the nanoparticles with high conductivity, and there was no difference in the critical heat flux when the same material nanoparticles were deposited on the two different specimen surfaces.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.539-540
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• 2021

In this paper, we consider the management scheme of the crowd group in the sensor networks. In the case of the networks searching the critical area, the operation of crowd group can affect the mission implement. The mobile sink system leading the group networks can change the network configuration as the dangerous data gathered from group sensor nodes. The dynamic network management provides the important role to the mission of mobile sink to react the dangerous environments.

• Molecules and Cells
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• v.37 no.10
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• pp.753-758
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• 2014

Sorting nexin 9 (SNX9) is a member of the sorting nexin family of proteins and plays a critical role in clathrinmediated endocytosis. It has a Bin-Amphiphysin-Rvs (BAR) domain which can form a crescent-shaped homodimer structure that induces deformation of the plasma membrane. While other BAR-domain containing proteins such as amphiphysin and endophilin have an amphiphatic helix in front of the BAR domain which plays a critical role in membrane penetration, SNX9 does not. Thus, whether and how SNX9 BAR domain could induce the deformation of the plasma membrane is not clear. The present study identified the internal putative amphiphatic stretch in the $1^{st}$ ${\alpha}$-helix of the SNX9 BAR domain and proved that together with the N-terminal helix ($H_0$) region, this internal putative amphiphatic stretch is critical for inducing membrane tubulation. Therefore, our study shows that SNX9 uses a unique mechanism to induce the tubulation of the plasma membrane which mediates proper membrane deformation during clathrinmediated endocytosis.

• Journal of Korean Academy of Nursing Administration
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• v.21 no.2
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• pp.154-163
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• 2015

Purpose: This descriptive study was done to identify factors that influence stress related to clinical practice for nursing students. Methods: Structured questionnaires were used to collect data from 278 students from two nursing colleges located in G metropolitan city and one nursing college in C region. Results: The factors that most influenced stress for the nursing students during their clinical practice were critical thinking disposition, clinical competence, year, and gender. Especially, the result showed that higher critical thinking disposition and clinical competence correlated with lower stress in clinical practice. Conclusion: The results indicate that improving nursing students' critical thinking ability and clinical competence would help to relieve stress during clinical practice and increase the ability to cope with stress efficiently. The development of a variety of teaching and learning strategies and education in both theoretical and clinical practice education would be necessary to achieve this goal.

• Journal of the Korean GEO-environmental Society
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• v.7 no.3
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• pp.69-76
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• 2006

In this study, an experimental study in sand ground that was prepared by raining method was performed for modeling the bearing capacity behavior of strip footing above a cavity. The critical range of bearing capacity of the strip footing affected by underground cavity was investigated by comparing results between experiment and theory. The size of the critical region depends on several factors such as footing shape, soil property, cavity size and cavity shape. The ultimate bearing capacity was more influenced by the depth of the underground cavity than the eccentricity of the underground. In addition, an underground cavity influences on not only the decrease of the bearing capacity, but also the differential settlement of a strip footing.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.1
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• pp.43-50
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• 2000

In this study, experiments were carried out to measure the variations in the corrosion potential and current density of polarization curves using polycarbonate. The results were particularly examined to identify the influences affecting the corrosion potential including various conditions such as temperature, pH, catalytic enzyme, and salt. The lines representing the active anodic dissolution were only slightly shifted in the potential direction by temperature, pH, enzyme, and salt. The tafel slope for the anodic dissolution was determined based on the polarization effect with various conditions. The slope of the polarization curves describing the active-to-passive transition region were noticeably shifted in direction. Also, from the variation in the conditions, the optimum conditions were established for the most rapid transformation, including temperature, pH, corrosion rate, and resistance of corrosion potential. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity(Ir/If). The value of Ir/If was then used in measuring the extent of the critical corrosion sensitivity of the polycarbonate. The potentiodynamic parameters of the corrosion were obtained using a Tafel plot.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1660-1662
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• 1996

Superconducting current lead is one of the promising applications of the oxide high-Tc superconductors, because they have the advantage of decreasing heat conduction to low temperature region, comparing with a conventional cooper alloy lead. High critical current density is a key factor for the applications such as current lead. $(Bi,Pb)_{2}Sr_{2}Ca_{2}Cu_{3}O_{x}$ high Tc superconductor hase been investigated in terms of critical current density. Bi-2223 superconducting current lead made by CIP and solid state sintering process. Bi-2223 current lead that heat treated at $836\;^{\circ}C$ for 240 h in 1/13 $PO_2$ had over $500\;A/cm^2$ of critical current density at 77K. We knew that the superconducting properties of tube type current leads were better than rods type of them. And we investigated the relation of Bi-2223 formation and heat treatment condition by XRD and SEM analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.923-930
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• 2003

We jointed Bi(Pb)-Sr-Ca-Cu-O multifilament tapes and evaluated their electrical and mechanical properties. In order to improve connectivity of multifilaments, one or two single-filament tape was inserted between two multifilament tapes. The critical current ratio(CCR) and n-value of the jointed tapes were evaluated as a function of uniaxial pressure. It was observed that critical current ratio and n-value were 24.8-29.0% and 2.5-2.8 for MM lap-jointed tape. On the other hand, the corresponding values were improved to 24.7-53.9% and 3.1-4.2 for MSM jointed tape, and 63.4-76.0% and 3.4-5.1 for double MS:vr lap-jointed tape, respectively. The highest electrical properties of double MSM lap-jointed tape are considered to be owing to the presence of single core, causing better interconnections of multifilaments between the two tapes. The mechanical property of jointed tape was evaluated and correlated to the microstructural evolution. The strength of jointed tapes was 44-64% less than that of the unjoined tape. The strain tolerance of jointed tape was also reduced compared to that of the unjoined tape. These lower mechanical properties of jointed tape are probably due to the induced nonuniform microstructure such as the existence of cracks and Ag-intrusion in the joined region.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1355-1364
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• 2001

Characteristics of secondary vortices is topologically investigated in the near-wake region of a circular cylinder, where the Taylor's hypothesis does nut hold. The three-dimensional flow fields in the wake-transition regime were measured by a time-resolved PIV for various planes of view. The convection velocities of the Karman and secondary vortices are evaluated from the trajectory of the vortex center. Then, saddle points are determined by applying the critical point theory. It is shown that the inclination angle of the secondary vortices agrees well with the previous experimental data. The flow fields in a moving frame of reference have several critical points and the mushroom-like structure appears in the streamline patterns of the secondary vortices. Since the distributions of fluctuating Reynolds stresses defined by triple decomposition are closely related with the existence of secondary vortices, the physical meaning of them is explained in conjunction with the vortex center and saddle point trajectories.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.2
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• pp.139-148
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• 2016

The passive control methods such as horizontal and vertical fences on the lower surface of the bluff body were applied to suppress the vortex shedding and enhance the aerodynamic stability of flow. For investigating the effects of the passive control methods, wind tunnel experiments on the unsteady flow field around a bluff body near a moving ground were performed. The boundary layer and velocity profiles were measured by the Hot Wire Anemometer (HWA) system and the vortex shedding patterns and flow structures in a wake region were visualized via the Particle Image Velocimetry (PIV) system. Also, it is a measuring on moving ground condition that the experimental values of the critical gap distances, Strouhal numbers and aerodynamic force FFT analyses. Through the experiments, we found that the momentum supply due to moving ground caused the vortex shedding at the lower critical gap distance rather than that of fixed ground. The horizontal and vertical fences increase the critical gap distance and it can suppress the vortex shedding. Consequently, the stability characteristics of the bluff body near a moving ground could be effectively enhanced by the simple passive control such as the vertical fences.