• The Journal of Internal Korean Medicine
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• v.41 no.6
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• pp.993-1014
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• 2020

Objective: Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. Antioxidant stress and inflammatory reactions are important causes of neurodegenerative diseases and are major causes of PD. Many animal experiments have been aimed at treating PD using the antioxidant effects of various traditional medicines and dietary supplements. This review reports the research investigating the antioxidant effects of herbs in in vivo PD models. Methods: The study consisted of a database search for articles related to PD and herbal treatments using the OASIS, NDSL, KTKP, Korean KISS, PubMed, Science Direct, CNKI, Wanfang, and J-STAGE databases. The search period was limited from the start of the search engine application to November 14, 2019. Studies were selected to confirm the antioxidant effects of herbal medicines in an in vivo PD model. Results: Eighty-two studies were summarized for plant species, extracts (or compounds), animal models, neurotoxins, and functional results. The most frequently used herbal materials were Bacopa monnieri, Camellia sinensis, Centella asiatica, and Withania somnifera. MPTP and 6-OHDA were the most commonly used neurotoxins for inducing PD. Most studies confirmed an increased expression and activation of antioxidant enzymes and a decrease in oxidative stress. Herbal materials showed their antioxidant effects regardless of the order of treatment and confirmed their possible use as treatments for the prevention and treatment of neurodegeneration. Conclusion: Many herbal medicines have antioxidant effects and are likely to be effective in delaying neurodegenerative damage by inhibiting or reducing oxidative stress by expression of antioxidant enzymes.

• Wind and Structures
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• v.32 no.3
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• pp.227-238
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• 2021

This study analyzed the pressure patterns and local pressure of tall buildings with corner modifications (recessed and chamfered corner) using wind tunnel tests and proper orthogonal decomposition (POD). POD can distinguish pressure patterns by POD mode and more dominant pressure patterns can be found according to the order of POD modes. Results show that both recessed and chamfered corners effectively reduced wind-induced responses. Additionally, unique effects were observed depending on the ratio of corner modification. Tall building models with recessed corners showed fluctuations in the approaching wind flow in the first POD mode and vortex shedding effects in the second POD mode. With large corner modification, energy distribution became small in the first POD mode, which shows that the effect of the first POD mode reduced. Among building models with chamfered corners, vortex shedding effects appeared in the first POD mode, except for the model with the highest ratio of corner modifications. The POD confirmed that both recessed and chamfered corners play a role in reducing vortex shedding effects, and the normalized power spectral density peak value of modes showing vortex shedding was smaller than that of the building model with a square section. Vortex shedding effects were observed on the front corner surfaces resulting from corner modification, as with the side surface. For buildings with recessed corners, the local pressure on corner surfaces was larger than that of side surfaces. Moreover, the average wind pressure was effectively reduced to 88.42% and 92.40% in RE1 on the windward surface and CH1 on the side surface, respectively.

• The Journal of the Korea Contents Association
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• v.21 no.2
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• pp.68-77
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• 2021

The purpose of this study is to The exhibition's service quality was divided into three factors: event content, publicity, and empathy. First, the exhibition's service quality had positive effects on visitors' perceived value and overall satisfaction. Visitors' perceived value also showed a positive effect on their overall satisfaction. Second, each of visitors' perceived value and overall satisfaction had positive effects on their loyalty. Third, in effect decomposition, the total effect of the exhibition's service quality on visitors' perceived value was largest, followed by the service quality's total effect on their overall satisfaction and the service quality's total effect on their loyalty in order. In addition, statistically significant total effects were found between visitors' perceived value and overall satisfaction, as well as between visitors' perceived value and loyalty. As a result, mediating effects such as visitors' overall satisfaction had a positive contribution. Accordingly, statistically significant effects were confirmed in the relationships between all endogenous and exogenous variables.

• Structural Engineering and Mechanics
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• v.73 no.3
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• pp.319-330
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• 2020

This paper investigates the free vibrations of cylindrical shells made of time-dependent materials for different viscoelastic models under various boundary conditions. During the extraction of equations, the displacement field is estimated through the first-order shear deformation theory taking into account the transverse normal strain effect. The constitutive equations follow Hooke's Law, and the kinematic relations are linear. The assumption of axisymmetric is included in the problem. The governing equations of thick viscoelastic cylindrical shell are determined for Maxwell, Kelvin-Voigt and the first and second types of Zener's models based on Hamilton's principle. The motion equations involve four coupled partial differential equations and an analytical method based on the elementary theory of differential equations is used for its solution. Relying on the results, the natural frequencies and mode shapes of viscoelastic shells are identified. Conducting a parametric study, we examine the effects of geometric and mechanical properties and boundary conditions, as well as the effect of transverse normal strain on natural frequencies. The results in this paper are compared against the results obtained from the finite elements analysis. The results suggest that solutions achieved from the two methods are ideally consistent in a special range.

• Advances in aircraft and spacecraft science
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• v.5 no.1
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• pp.129-139
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• 2018

The composite materials are widely used in aircraft structures. Their relative rigidity/weight gives them an important advantage over the metal structures. The objective of this work is to analyze by the finite element method the mechanical behavior of composite plate type notched with various forms under tensile load. Two basic parameters were taken into consideration. The first, the form of the notch in order to see its effect on the stress and the failure load. The second, we studied the influence of the locale orientation of fiber around the plate's notch. These parameters are studied in order to see their effects on the distribution stress and failure load of the plate. The calculation of the failure load is determined numerically with the numerical code ABAQUS using the XFEM (extended Finite Element Modeling) based on the fracture mechanics. The result shows clearly that it is important to optimize the effect of fiber orientation around the notch.

• Journal of KSNVE
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• v.7 no.1
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• pp.117-125
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• 1997

The aim of this research is to measure the damage caused by the vibrations of passing trains. In order to determine the vibration levels of the trains, twelve points along the Honam, Cholla and Kyungjun lines were chose. There are two goals to be achieved from the data gathered. The first is to determine whether or not the trains are operating under governmentally determined levels. The second goal is to establish countermeasure in order to minimize the effects of the vibrations on the people who live near the train lines. A vibration level meter was used to measure the vibration levels at all twelve points at times when no trains were travelling and at times when trains were travelling. As a result, it was found that Saemaeulho and Mugunghwaho, had a higher vibration level of 2 - 3 dB than Pidulgiho and freight trans. There were no relationship between speed and vibration level. The vibration levels did change according to capacity and size of the engine. In such cases there was a difference of 2 - 7 dB. Where vibration proof ditches were in place, the vibration level were decreased by 3 - 6 dB. The practical decreases in vibration levels was similar to the theoretical decreases.

• Journal of Advanced Research in Ocean Engineering
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• v.3 no.2
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• pp.83-101
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• 2017

In this study, the added resistances of the large container ship in head and oblique seas are evaluated using a time-domain Rankine panel method. The mean forces and moments are computed by the near-field method, namely, the integration of the second-order pressure directly on the ship surface. Furthermore, a weakly nonlinear approach in which the nonlinear restoring and Froude-Krylov forces on the exact wetted surface of a ship are included in order to examine the effects of amplitudes of waves on ship motions and added resistances. The computation results for various advance speeds and heading angles are validated by comparing with the experimental data, and the validation shows reasonable consistency. Nevertheless, there exist discrepancies between the numerical and experimental results, especially for a shorter wave length, a higher advance speed, and stern quartering seas. Therefore, the accuracies of the linear and weakly nonlinear methods in the evaluation of the mean drift forces and moments are also discussed considering the characteristics of the hull such as the small incline angle of the non-wall-sided stern and the fine geometry around the high-nose bulbous bow.

• Structural Engineering and Mechanics
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• v.58 no.2
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• pp.347-378
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• 2016

Within the scope of the plane-strain state, by utilizing the three-dimensional linearized theory of elastic waves in initially stressed piezoelectric and elastic materials, Lamb wave propagation and the influence of the initial stresses on this propagation in a sandwich plate with pre-stressed piezoelectric face and pre-stressed metal elastic core layers are investigated. Dispersion equations are derived for the extensional and flexural Lamb waves and, as a result of numerical solution to these equations, the corresponding dispersion curves for the first (fundamental) and second modes are constructed. Concrete numerical results are obtained for the cases where the face layers' materials are PZT-2 or PZT-6B, but the material of the middle layer is Steel (St) or Aluminum (Al). Sandwich plates PZT-2/St/PZT-2, PZT-2/Al/PZT-2, PZT-6B/St/PZT-6B and PZT-6B/Al/PZT-6B are examined and the influence of the problem parameters such as piezoelectric and dielectric constants, layer thickness ratios and third order elastic constants of the St and Al on the effects of the initial stresses on the wave propagation velocity is studied.

• Wind and Structures
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• v.15 no.3
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• pp.189-208
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• 2012

Lock-in and drag amplification phenomena are studied for a flexible cantilever using a simplified fluid-structure interaction approach. Instead of solving the 3D domain, a simplified setup is devised, in which 2D flow problems are solved on a number of planes parallel to the wind direction and transversal to the structure. On such planes, the incompressible Navier-Stokes equations are solved to estimate the fluid action at different positions of the line-like structure. The fluid flow on each plane is coupled with the structural deformation at the corresponding position, affecting the dynamic behaviour of the system. An Arbitrary Lagrangian-Eulerian (ALE) approach is used to take in account the deformation of the domain, and a fractional-step scheme is used to solve the fluid field. The stabilization of incompressibility and convection is achieved through orthogonal quasi-static subscales, an approach that is believed to provide a first step towards turbulence modelling. In order to model the structural problem, a special one-dimensional element for thin walled cross-section beam is implemented. The standard second-order Bossak method is used for the time integration of the structural problem.

• Journal of the Korean Wood Science and Technology
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• v.46 no.4
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• pp.380-392
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• 2018

The importance of polysaccharides is increasing globally due to their role as a significant source of dietary prebiotics in the human diet. In the present study, in order to maximize the yield of crude polysaccharides from Pinus densiflora, response surface methodology (RSM) was used to optimize a two-stage extraction process consisting of steam explosion and water extraction. Three independent main variables, namely, the severity factor (Ro) for the steam explosion process, the water extraction temperature ($^{\circ}C$), and the ratio of water to raw material (v/w), were studied with respect to prebiotic sugar content. A Box-Behnken design was created on the basis of the results of these single-factor tests. The experimental data were fitted to a second-order polynomial equation for multiple regression analysis and examined using the appropriate statistical methods. The data showed that both the severity factor (Ro) and the ratio of water to material (v/w) had significant effects on the prebiotic sugar content. The optimal conditions for the two-stage process were as follows: a severity factor (Ro) of 3.86, a water extraction temperature of $89.66^{\circ}C$, and a ratio of water to material (v/w) of 39.20. Under these conditions, the prebiotic sugar content in the extract was 332.45 mg/g.