• Korean Journal of Exercise Nutrition
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• v.23 no.3
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• pp.39-44
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• 2019

[Purpose] Weight loss can reduce obesity-induced arterial stiffening that is attributed to decreased inflammation. Angiopoietin-like protein 2 (ANGPTL2) is a pro-inflammatory adipokine that is upregulated in obesity and is important in the progression of atherosclerosis and cardiovascular disease. The purpose of this study is to investigate the effects of dietary modification on circulating ANGPTL2 levels and arterial stiffness in overweight and obese men. [Methods] Twenty-two overweight and obese men (with mean age of 56 ± 2 years and body mass index of 28.6 ± 2.6 kg/m²) completed a 12-week dietary modification program. We measured the arterial compliance and β-stiffness index (as the indices of arterial stiffness) and serum ANGPTL2 levels before and after the program. [Results] After the 12-week dietary modification, body mass and daily energy intake were significantly reduced. Arterial compliance was significantly increased and β-stiffness index was significantly decreased after the 12-week dietary modification program. Serum ANGPTL2 levels were significantly decreased. Also, the changes in arterial compliance were negatively correlated with the changes in serum ANGPTL2 levels, whereas the changes in β-stiffness index were positively correlated with the changes in serum ANGPTL2 levels. [Conclusion] These results suggest that the decrease in circulating ANGPTL2 levels can be attributed to the dietary modification-induced reduction of arterial stiffness in overweight and obese men.

• Design & Manufacturing
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• v.12 no.2
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• pp.40-45
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• 2018

Recently, in construction equipment machinery production, development has focused on environmentally-friendly functions to improve existing production capacity. For excavators as well, emphasis has been placed on response to environmental regulations, miniaturization, and noise reduction, while technology is being developed considering cost reduction and safety.Accordingly, the front support, an inner reinforcement part of the excavator, as well as high-strength steel plates to improve safety and reduce weight, are being applied.However, in the case of high-strength materials, Springback occurs in the final formed part due to high residual stress during product forming. Derivation of a forming or product shaping process to reduce springback is needed. Accordingly, regarding the front support, an inner reinforcement part of the excavator, this study derived a method to improve springback and secure shape stiffness through analysis of the springback occurrence rate and springback causes through a forming analysis.As for the results of analyzing the springback occurrence rate of existing products through forming analysis, springback of -22.6 mm < z < 27.35 mm occurred on the z-axis, and it was confirmed that springback occurred due to the stiffness reinforcing bead of the upper and middle parts of the product.To control product residual stress and springback, we confirmed a tendency of springback reduction through local pre-cutting and stiffness reinforcement bead relocation.In the local pre-cutting model, springback was slightly reduced by 5.3% compared with the existing model, an insignificant reduction effect. In the stiffness reinforcement bead relocation model, when an X-shaped stiffness reinforcement bead was added to each corner portion of the product, springback was reduced by at least 80%.The X-shaped bead addition model was selected as the springback reduction model, and the level of stiffness compared to the existing model was confirmed through a structural analysis.The X-shaped bead additional model showed a stress springback of 90% and springback reduction of 7.4% compared with the existing model, indicating that springback and stiffness will be reinforced.

• Structural Engineering and Mechanics
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• v.16 no.5
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• pp.597-612
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• 2003

In this paper, multi-story buildings with shear-wall structures and with narrow rectangular plane configuration are modeled as a multi-step flexural-shear plate with varying cross-section for buckling analysis. The governing differential equation of such a plate is established. Using appropriate transformations, the equation is reduced to analytically solvable equations by selecting suitable expressions of the distribution of stiffness. The exact solutions for buckling of such a one-step flexural-shear plate with variable stiffness are derived for several cases. A new exact approach that combines the transfer matrix method and closed from solution of one-step flexural-shear plate with continuously varying stiffness is presented for stability analysis of multi-step non-uniform flexural-shear plate. A numerical example shows that the present methods are easy to implement and efficient.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.187-194
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• 2002

Bridge dynamic behaviors and the failure of the foundation are examined in this study under seismic excitations including the local scour effect. The simplified mechanical model, which can consider the effect of various influence elements, is proposed to simulate the bridge motions. The scour depths around the foundations are estimated by the CSU equation recommended by the HEC-18 and the local scour effect upon global bridge motions is then considered by applying various foundation stiffness based upon the reduced embedded depths. From the simulation results, it is found that seismic responses of a bridge with the same scour depth for both foundations increase due to the local scour effect. The bridge scour is found to be significant under weak and moderate seismic intensity. The recovery durations of the foundation stiffness after local scour are found to be critical in the estimation of the probability of foundation failure under earthquakes. Therefore, the safety of the whole bridge system should be conducted with the consideration of the scour effect upon the foundations and the recovery duration of stiffness should be determined rationally.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.421-425
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• 2007

In the fabrication of dry adhesive structure, increasing contact-points or contact-area is the primary goal because the adhesive force grows in proportion to the contact-area. The simplest way to extend the contact surface is the fabrication by using soft materials. However, the column-array structure could confront the matting phenomenon which columns are stuck together. Therefore, we need a novel design to reduce the effective stiffness with adequate stiff materials like a gecko's setae. In this study, we propose a novel design for the dry adhesive structure. Moreover, we analyzed whether the adhesive structure conforms the rough surface sufficiently through finite element method adopted the non-bonding interaction as the body force. Also, we fabricated the novel structures via UV lithography and some techniques. In addition, we examined the adhesive force of the novel structures.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.109-119
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• 2002

In this paper, mechanism design of optical pickup actuator for fast access is proposed. This actuator is composed of moving magnet type actuator and moving coil type actuator for tracking and fine motion, respectively. Moving magnet type tracking actuator is configurated by two permanent magnets and four air-core solenoids. Additional damper by induced current in tracking actuator can reduce the transient vibration between the coarse seeking servo and fine seeking servo. Variable stiffness can be acquired by applying current to air-core solenoid simply. This actuator can achieve fast access by these additional damper and stiffness. Performance of this actuator is predicted through the FEM, simulation and simple experiment. Settling time for transient vibration is reduced to 14.7% according to simulation result.

• Journal of KSNVE
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• v.9 no.3
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• pp.517-524
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• 1999

Mathematical formulas for multi-dimensional isolation analysis via vibrational power transmission can be derived in a rather simple form when the wave effects of the isolators are completely neglected. With increase of frequency range of interest, however, the wave effects play a very important role and hence cannot be neglected. The formulas get involved accordingly. In this study, a method of equivalent stiffness modeling of the isolators to include the wave effects is proposed in such a way that not only the complexity of the mathematical expressions but also that of experiments of necessity can be reduced. This method is illustratively applied to a two-dimensional vibration isolation system with nonrigid source and base structures.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.2
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• pp.114-121
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• 2010

As a vehicle speed increases, more vibration energy is transmitted from chassis to a driver. Current isolation system for the driver's seat by damping control can reduce the transmitted vibration energy near resonance area. But in higher frequency region than natural frequency multiplied by $\sqrt{2}$, the vibration energy transmitted to the driver has a tendency to be increased. Therefore, the method by natural frequency reduction of the system is preferred to increase the effectiveness of the anti-vibration. However, the natural frequency could not be freely reduced due to the nature of the isolation system structure. A new passive suspension system to reduce the natural frequency is proposed. The theoretical analysis and experimental results show better vibration attenuation compared with the current isolation system.

• Steel and Composite Structures
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• v.7 no.5
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• pp.391-404
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• 2007

This paper presents push-out tests of stud shear connectors to examine their fatigue behavior for developing a new composite bridge deck system. The fifteen push-out specimens of D16 mm stud welded on 9 mm steel plate were fabricated according to Eurocode-4, and a series of fatigue endurance test and residual strength test were performed. Additionally, the stiffness and strength variations by cyclic loading were compared. The push-out test, when the stiffness reduction ratio of the specimens was 0.95 under cyclic load, resulted in the failure of the studs. The stiffness variation of the push-out specimens additionally showed that the application of cyclic loads reduced the residual strength. The fatigue strength of the shear connectors were compared with the design values specified in the Eurocode-4, ASSHTO LRFD and JSSC codes. The comparison result showed that the fatigue endurance of the specimens satisfies the design values of these codes.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.296-326
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• 1994

The purpose of this study was to evaluate the mechanical effects when one implant fixture was connected to the natural teeth with reduced alveolar bone height. This study also examined the effects of increasing the number of abutment teeth and the effects of the intramobile connector and the titanium connector as they were inserted between the implant superstructure and the fixture. The distribution and concentration load was applied to the fixed partial denture(FPD) supported by implant and the natural teeth with reduced alveolar bone height. The stress and displacement of each element was observed and compared by the two-dimensional finite element method. The following results were obtained : 1. The greater the loss of alveolar bone in natural teeth area, the greater the displacement of FPD and the stress concentration in alveolar bone around implant, especially at the stress concentration in the mesial alveolar bone crest around implant fixture. 2. The displacement of FPD was increased more and that of implants fixture was decreased more when intramobile connector was used than titanium connector was used. Also the stress concentration in alveolar bone around implant fixture was greater when intramobile connector than titanium connector. One implication of this finding was that the difference in stiffness of implant and the natural teeth with reduced alveolar bone height could be partially compensated in case of the POM intramobile connector. 3. The amount and direction of displacement and the stress distribution of the 4-unit FPD was better than those of the 3-unit FPD. It implied that the difference of stiffness of implant and natural teeth with reduced alveolar bone height could be partially compensated in case of the 4 unit FPD.