• Steel and Composite Structures
• /
• v.32 no.3
• /
• pp.293-304
• /
• 2019

In the present paper, the element free Galerkin (EFG) method is developed for geometrically nonlinear analysis of deep beams considering small scale effect. To interpret the behavior of structure at the nano scale, the higher-order gradient elasticity nonlocal theory is taken into account. The radial point interpolation method with high order of continuity is used to construct the shape functions. The nonlinear equation of motion is derived using the principle of the minimization of total potential energy based on total Lagrangian approach. The Newmark method with the small time steps is used to solve the time dependent equations. At each time step, the iterative Newton-Raphson technique is applied to minimize the residential forces caused by the nonlinearity of the equations. The effects of nonlocal parameter and aspect ratio on stiffness and dynamic parameters are discussed by numerical examples. This paper furnishes a ground to develop the EFG method for large deformation analysis of structures considering small scale effects.

• Coupled systems mechanics
• /
• v.13 no.2
• /
• pp.153-170
• /
• 2024

The problem considered in this theoretical paper is the delamination of a multilayered inhomogeneous beam structure that has viscoelastic behaviour under angle of twist, horizontal and vertical displacements which vary smoothly with time according to prescribed laws. The cross-section of the beam is a rectangle. The layers are made of different materials which are smoothly inhomogeneous along the length of the beam. The beam under consideration represents statically undetermined structure since it is clamped in its two ends. The problem of the strain energy release rate is solved. For this purpose, the strain energy stored in the beam structure is analyzed. In order to verify the solution obtained, the strain energy release rate is found also analyzing the time-dependent compliances of the beam under prescribed angle of twist and displacements. A parametric investigation is carried-out by applying the solution obtained. Special attention is paid to the effect of the parameters which control the variation of the angle of twist and the displacements with time on the strain energy release rate.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.317-320
• /
• 2002

The effect of vibration on the viscosity of a shear-thinning fluid was investigated with a newly designed pressure-scanning capillary viscometer. The viscometer was designed to measure non-Newtonian viscosity continuously over a range of shear rates at a time. Low frequency vibration was applied perpendicularly to the direction of the flow. The effect of the transversal vibration was investigated for both Newtonian fluids and non-Newtonian fluids. The experimental results showed that the vibration had no effect on the viscosity of the Newtonian fluids. However, the vibration caused a significant reduction of the shear-thinning fluid viscosity. The viscosity reduction was strongly dependent on both vibration frequency and shear rate. In addition, the viscosity reduction was affected by the amplitude of vibration, and, the bigger amplitude applied, the more viscosity reduction occurred.

• The Korean Journal of Physiology and Pharmacology
• /
• v.26 no.4
• /
• pp.277-285
• /
• 2022

To investigate the adverse effects of clozapine on cardiovascular ion channels, we examined the inhibitory effect of clozapine on voltage-dependent K⁺ (Kv) channels in rabbit coronary arterial smooth muscle cells. Clozapine-induced inhibition of Kv channels occurred in a concentration-dependent manner with an half-inhibitory concentration value of 7.84 ± 4.86 µM and a Hill coefficient of 0.47 ± 0.06. Clozapine did not shift the steady-state activation or inactivation curves, suggesting that it inhibited Kv channels regardless of gating properties. Application of train pulses (1 and 2 Hz) progressively augmented the clozapine-induced inhibition of Kv channels in the presence of the drug. Furthermore, the recovery time constant from inactivation was increased in the presence of clozapine, suggesting that clozapine-induced inhibition of Kv channels is use (state)-dependent. Pretreatment of a Kv1.5 subtype inhibitor decreased the Kv current amplitudes, but additional application of clozapine did not further inhibit the Kv current. Pretreatment with Kv2.1 or Kv7 subtype inhibitors partially blocked the inhibitory effect of clozapine. Based on these results, we conclude that clozapine inhibits arterial Kv channels in a concentration-and use (state)-dependent manner. Kv1.5 is the major subtype involved in clozapine-induced inhibition of Kv channels, and Kv2.1 and Kv7 subtypes are partially involved.

• The Korean Journal of Physiology and Pharmacology
• /
• v.14 no.3
• /
• pp.185-189
• /
• 2010

The present study demonstrates the effect of fibrates, agonists of $PPAR{\alpha}$ on cytokines-induced proliferation in primary cultured astrocytes. Alone or combination treatment with cytokines, such as IL-$1{\beta}$ (10 ng/ml), $IFNP{\gamma}$ (10 ng/ml), and TNF-$\alpha$ (10 ng/ml) cause a significant increase of cell proliferation in a time-dependent manner. Treatment of astrocytes with bezafibrate and fenofibrate (0, 5, and $10\;{\mu}M$) reduced the $IFNP{\gamma}$ and IL-$1{\beta}$-induced cell proliferation in a dose-dependent manner. To address the involvement of IL-6 on the $IFNP{\gamma}$ and IL-$1{\beta}$-induced cell proliferation, released IL-6 level was measured. $IFNP{\gamma}$ and IL-$1{\beta}$ cause an increase of released IL-6 protein level in a time-dependent manner. Furthermore, pretreatment with IL-6 antibody (0, 0.1, 1, 2.5, and 5 ng/ml) dose-dependently inhibited the $IFNP{\gamma}$ and IL-$1{\beta}$-induced cell proliferation. However, bezafibrate and fenofibrate did not affect increased mRNA and protein levels of IL-6 in $IFNP{\gamma}$ and IL-$1{\beta}$-stimulated astrocytes. Taken together, these results clearly suggest that activation of $PPAR{\alpha}$ attenuates the $IFNP{\gamma}$ and IL-$1{\beta}$-induced cell proliferation through IL-6 independent pathway.

• Biomolecules & Therapeutics
• /
• v.20 no.3
• /
• pp.299-305
• /
• 2012

Endochondral bone formation is the process by which mesenchymal cells condense to become chondrocytes, which ultimately form new bone. The process of chondrogenic differentiation and hypertrophy is critical for bone formation and as such is regulated by many factors. In this study, we aimed to indentify novel factors that regulate chondrogenesis. We investigated the possible role of isopsoralen in induction of chondrogenic differentiation in clonal mouse chondrogenic ATDC5 cells. Isopsoralen treatment stimulated the accumulation of cartilage nodules in a dose-dependent manner. Further, ATDC5 cells treated with isopsoralen were stained more intensely with Alcian blue than control cells, suggesting that isopsoralen increases the synthesis of matrix proteoglycans. Similarly, isopsoralen markedly induced the activation of alkaline phosphatase activity compared with control cells. Isopsoralen enhanced the expressions of chondrogenic marker genes such as collagen II, collagen X, OCN, Smad4 and Sox9 in a time-dependent manner. Furthermore, isopsoralen induced the activation of extracellular signal-regulated kinase (ERK) and p38 MAP kinase, but not that of c-jun N-terminal kinase (JNK). Isopsoralen significantly enhanced the protein expression of BMP-2 in a time-dependent manner. PD98059 and SB 203580, inhibitors of ERK and p38 MAPK, respectively, decreased the number of stained cells treated with isopsoralen. Taken together, these results suggest that isopsoralen mediates a chondromodulating effect by BMP-2 or MAPK signaling pathways, and is therefore a possible therapeutic agent for bone growth disorders.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.36 no.2
• /
• pp.105-112
• /
• 2023

In this study, structural analyses were conducted to analyze the performance of a bridge to which friction pendulum systems (FPSs) were applied using different friction models. A Coulomb friction model and a rate dependent friction model were constructed using the friction coefficient of a PVDF/MgO friction material to analyze the effect of different friction analysis models. The Coulomb friction model uses a single friction coefficient regardless of friction velocity, while the rate dependent friction model can reflect the change in the friction coefficient with friction velocity. Nonlinear time history and seismic fragility analyses were conducted to confirm responses of the bridge. The seismic responses of a deck and a column were used to evaluate the performance of the base isolated bridge, and a friction model that can effectively evaluate the performance of isolated bridges was analyzed.

• Korean Journal of Food Science and Technology
• /
• v.22 no.4
• /
• pp.466-472
• /
• 1990

The effect of sugar addition and heat treatment on the myofibrillar protein extractability was studied. Maillard reaction was dependent on heating time significantly and glucose revealed the highest reactivity for Maillard reaction. The extractability of myofibrillar proteins was lowest in case of glucose addition and decreased according to increasing of heating time, Higher extractability was resulted in by digestion of myofibrillar proteins with enzymes after sugar addition and heat treatment than the undigested samples, as the sample was digested with trypsin that is the highest. And by digestion with trypsin, chymotrypsin and peptidase at a time the extractability of meat proteins increased remarkably.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.2
• /
• pp.97-103
• /
• 1984

Post weld heat treatment(PWHT) of weldment of the low alloy steel is carried out to remove residual stress existing in weldment and to improve fracture toughness, but it is often observed that there occurs grain boundary failure and that fracture toughness decreases in weld heat affected zone(HAZ)because of PWHT. In this paper, the effect of heating rate and holding time of PWHT on fracture toughness were evaluated by crack opening displacement (CDD)test and micro-hardness test under the constant stress simulated residual stress in HAZ of Cr-Mo steel. The experimental results are as follow; (1)Transition temperature of weld HAZ after PWHT was dependent upon heating rate greater than holding time, and fracture toughness was decreased with an increase of the heating rate. (2)Softening ration of the notch tip was increased with holding time within one hour and saturated after one hour, but under applied stress it was increasing continuously. (3)The average hardness value in weld HAZ was increased with heating rate of PWHT.

• Ocean and Polar Research
• /
• v.26 no.3
• /
• pp.475-480
• /
• 2004

Recently, less toxic and more effective anaesthetics are essential for marine fishes. Lidocaine belongs to a group of anaesthetics which are used as local anaesthetic in human medicine. This chemical was tested fer winter flounder, Pleunnectes americanus. Anaesthetic effect of lidocaine hydrochloride-sodium bicarbonate mixture (lidocaine $HCl/NaHCO_3$) was tested for the winter flounder at five different temperature regimes: $3^{\circ}C,\;7^{\circ}C,\;11^{\circ}C,\;15^{\circ}C\;and\;19^{\circ}C$ Anaesthetic dose and temperature-dependent relationship in exposure and recovery time were observed for the winter flounder of $17.2{\pm}0.1cm$ mean total length. Based on the results, anaesthetic lidocaine $HCl/NaHCO_3$ showed rapid exposure time and rapid recovery time for winter flounder. The results indicate that lidocaine $HCl/NaHCO_3$ can be used as suitable anaesthetic for this species.