• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.945-949
• /
• 2003

In this paper, we present that now and heat transfer characteristics of oscillatory impinging jet which have been numerically investigated using parallel computations. Numerical value were obtained for dimensionless distance H=4, dimensionless outlet length L=45 and Reynolds number Re= 1500. It was found that the oscillatory impinging jet generated the regular heat transfer area even though the maximum heat transfer is lower than nonoscillatory impinging jet. We also found that heat transfer depends on the period of nozzle for the oscillatory impinging jet.

• Kyungpook Mathematical Journal
• /
• v.27 no.1
• /
• pp.7-13
• /
• 1987

This paper is a study of the oscillatory and asymptotic behaviour of solutions of the second order nonhomogeneous linear differential equation y"+P(x)y=f(x), and the associated homogeneous equation. Conditions are determined, under which the nonhomogeneous equation is oscillatory if and only if the homogeneous equation is oscillatory.

• Bulletin of the Korean Mathematical Society
• /
• v.59 no.1
• /
• pp.191-202
• /
• 2022

In this paper, we obtain the quantitative weighted bounds of oscillatory singular integral with rough kernel. Moreover, the quantitative weighted bounds of maximally truncated oscillatory singular integral with rough kernel are also obtained.

• The Korean Journal of Physiology
• /
• v.29 no.1
• /
• pp.103-111
• /
• 1995

Intracellular recordings were obtained from Purkinje cells in rat cerebellar slices maintained in vitro. Adding tetrodotoxin to the superfusion solution produced a typical pattern of repetitive burst firing consisting of a cluster of action potentials followed by a long hyperpolarization. TTX-induced oscillatory activity was not due to modulation of membrane potential although underlying mechanisms for maintenance of oscillatory activity were influenced by membrane voltage. The mechanism of TTX-induced oscillation was not related to the presence or amplitude of $I_h$ and could still induce the oscillatory activity after blockade of $I_h$ by cesium. The result from an experiment in which QX-314 was injected intracellularly strongly suggested that TTX-induced oscillatory firing activity was due to blockade of post-synaptic $Na^{+}$ currents intrinsic to PCs.

• The Korean Journal of Physiology and Pharmacology
• /
• v.1 no.5
• /
• pp.477-484
• /
• 1997

Intracellular recordings of oscillatory firing (bursting activity) were obtained from Purkinje cells (PCs) in rat cerebellar slices. Apamin inhibited post-burst hyperpolarizations (PBHs) progressively and finally terminated oscillatory firing activity of PCs. Apamin did not affect the amplitude or duration of the after-hyperpolarization (AHP) between spikes within the burst. In the voltage clamp mode, apamin shifted the whole-cell, quasi-steady state I/V relationship in an inward direction and abolished the zero slope resistance (ZSR) region by blocking outward current. Nickel ($Ni^{2+}$) terminated oscillatory activity and also abolished the ZSR region. However, $Ni^{2+}$ did not have progressive blocking action on the post-burst hyperpolarization before it blocked oscillatory activity. $Ni^{2+}$ blocked an inward current at potentials positive to approximately -65 mV, which was responsible for the ZSR region and outward current at more negative potentials. These data indicated that oscillatory activity of PCs is sustained by a balance between a slow $Ni^{2+}$-sensitive inward current and an apamin-sensitive outward current in the region of ZSR of the whole-cell I/V curve.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.11 no.2
• /
• pp.923-938
• /
• 2019

Surge motion of top-end platform induced by periodic wave makes marine flexible riser encounter equivalent sheared-oscillatory flow, under which the Vortex-induced Vibration (VIV) response will be more complicated than pure sheared flow or oscillatory flow cases. Based on a time domain force-decomposition model, the VIV response characteristics under sheared-oscillatory flows are investigated numerically in this paper. Firstly, the adopted numerical model is validated well against laboratory experiments under sheared flow and oscillatory flow. Then, 20 sheared-oscillatory flow cases with different oscillation periods and top maximum current velocities are designed and simulated. Under long and short oscillation period cases, the structural response presents several similar features owing to the instantaneous sheared flow profile at each moment, but it also has some different patterns because of the differently varying flow field. Finally, the effects and essential mechanism of oscillation period and top maximum current velocity on VIV response are discussed systematically.

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.4
• /
• pp.817-824
• /
• 2001

In the present study, flow characteristics of turbulent oscillatory flows in the exit region connected to the square-sectional $180^{\circ}$curved duct was investigated experimentally. The experimental study for air flows was conducted to measure velocity profiles, shear stress distributions by using the Laser Doppler Velocimetry(L.D.V) system with the data acquisition and processing system of Rotating Machinery Resolver(R.M.R) and PHASE software. The results obtained from the experimentation were summarized as follows : The critical Reynolds number for a change from transitional oscillatory flow to turbulent oscillatory flow was about 75,000 in the 90 region of dimensionless axial position (x/Dh) which was considered as a fully developed flow region. In the turbulent oscillatory flow, velocity profiles of the inflow period in the entrance region were gradually developed, but those of the outflow period were not changed nearly. Shear stress distributions of turbulent oscillatory flow was gradually increased as the flow proceeds to downstream.

• Geomechanics and Engineering
• /
• v.18 no.1
• /
• pp.59-69
• /
• 2019

Grout injection is mainly used for permeability reduction and/or improvement of the ground by injecting grout material into pores, cracks, and joints in the ground. The oscillatory grout injection method was developed to enhance the grout penetration. In order to verify the level of enhancement of the grout, field grout injection tests, both static and oscillatory tests, were performed at three job sites. The enhancement in the permeability reduction and ground improvement effect was verified by performing a core boring, borehole image processing analysis, phenolphthalein test, scanning electron microscopy analysis, variable heat test, Lugeon test, standard penetration test, and an elastic wave test. The oscillatory grout injection increased the joint filling rate by 80% more and decreased the permeability coefficient by 33-68%, more compared to the static grout injection method. The constrained modulus of the jointed rock mass was increased by 50% more with oscillatory grout injection compared to the static grout injection, indicating that the oscillatory injection was more effective in enhancing the stiffness of the rock mass.

• Journal of applied mathematics & informatics
• /
• v.8 no.1
• /
• pp.111-128
• /
• 2001

In this paper, we consider the oscillation of the second-order neutral difference equation Δ²(x/sub n/ - px/sub n-r/) + q/sub n/f(x/sub n/ - σ/sub n/) = 0 as well as the oscillatory behavior of the corresponding ordinary difference equation Δ²z/sub n/ + q/sub n/f(R(n,λ)z/sub n/) = 0

• Korea-Australia Rheology Journal
• /
• v.19 no.3
• /
• pp.117-123
• /
• 2007

There has been considerable interest in recent years in field-responsive suspensions, which are of some importance in industry in many different applications. The microstructure of these materials is a significant issue which can be probed by rheological measurements. In this study, measurements were made of a magnetorheological fluid (MRF) under steady and oscillatory shear flow, with and without a magnetic field. Mathematical inversion was used to derive the relaxation time spectrum of the MRF from oscillatory shear data. Experimental evidence is presented of the gel-like properties of this MRF.