• Coupled systems mechanics
• /
• 제1권1호
• /
• pp.39-57
• /
• 2012

This study intends to explore dynamic interaction behaviors between actively controlled maglev vehicle and guideway girders by considering the nonlinear forms of electromagnetic force and current exactly. For this, governing equations for the maglev vehicle with ten degrees of freedom are derived by considering the nonlinear equation of electromagnetic force, surface irregularity, and the deflection of the guideway girder. Next, equations of motion of the guideway girder, based on the mode superposition method, are obtained by applying the UTM-01 control algorithm for electromagnetic suspension to make the maglev vehicle system stable. Finally, the numerical studies under various conditions are carried out to investigate the dynamic characteristics of the maglev system based on consideration of the linear and nonlinear electromagnetic forces. From numerical simulation, it is observed that the dynamic responses between nonlinear and linear analysis make little difference in the stable region. But unstable responses in nonlinear analysis under poor conditions can sometimes be obtained because the nominal air-gap is too small to control the maglev vehicle stably. However, it is demonstrated that this unstable phenomenon can be removed by making the nominal air-gap related to electromagnetic force larger. Consequently it is judged that the nonlinear analysis method considering the nonlinear equations of electromagnetic force and current can provide more realistic solutions than the linear analysis.

• 대한소아치과학회지
• /
• 제24권1호
• /
• pp.82-94
• /
• 1997

For the purpose of establishing the most appropriate method of bonding between glass ionomer liners and composite resin and comparing the materials for sandwich technique, an experiment was performed to measure the shear bond strengths between the two with the variables in the surface treatment of liners and elapsed time till composite buildup. Materials used were Vitrebond and Fuji II LC, each as the restorative and liner respectively, and each group was subdivided by surface treatment (acid etching and sandblasting) and time elapsed from GIC filling to composite buildup (immediately, 1 day, 7 days), consisting 12 groups as a whole. Each subgroup was composed of 10 specimens and the shear bond strength between GIC liners and composite resin was measured under UTM and analyzed. The result were as follows: 1. The shear bond strength between two materials was highest when initially filled Fuji II LC was sandblasted after 1 days and composite built-up (Group FS1). And the lowest value was found when GIC was acid-etched after 7 days and composite built-up (Group FE7). Significant difference was found between the two groups. (P<0.01) 2. In regard of surface treatment of GI liners, acid-etched group (VE) showed higher bond strength than sandblasted group (VS) for Vitrebond. But, the reverse was true for Fuji II LC. (P<0.05) 3. In regard to the time elapsed from GI filling to composite buildup, the group of 1 day elapse showed relatively higher strength for Vitrebond. On the contrary, immediate buildup group (FE0) was stronger for acid-etched group and 1 day elapse group(FS1) was higher for sand-blasted group in Fuji II LC. (P<0.05)

• 한국결정성장학회지
• /
• 제20권3호
• /
• pp.147-152
• /
• 2010

본 연구에서는 인공골재를 제조하기 위하여 저급 점토에 석탄회(Fly Ash와 Bottom Ash)를 각각 첨가하여, 여러 분석기기(SEM, XRD, XRF, TG-DTA, Dilatometer, UTM)를 이용하여 물리 화학적 특성을 조사하였다. Fly ash, bottom ash, clay의 화학조성은 $SiO_2$가 33.01, 53.73 및 68.36 wt% $Al_2O_3$는 28.54, 32.42 및 18.12 wt%와 이외에 $Fe_2O_2$와 알카리 성분 등이 함유하고 있다. 소성에 의한 인공골재의 치밀화 과정을 관찰하기 위해 Dilatometer를 측정하였다. 시편들은 $850^{\circ}C$ 부근에서 서서히 수축이 시작되어 $1100^{\circ}C$ 부근에서 급격하게 수축하는 것을 볼 수 있었다. 소성온도와 배합조성에 따른 시편의 결정상을 알아보기 위하여 $1150^{\circ}C$에서 30분간 열처리 하였으며 fly Ash를 사용한 시편의 주 결정상은 quartz, anorthite, albite상이 관찰되었고 bottom ash를 사용한 시편은 quartz, anorthite, mullite가 관찰되었다. $1150^{\circ}C$에서 소성한 시편에서 플라이애쉬 보다 바탐애쉬를 첨가한 시편이 압축강도가 우수 하며, 바탐애쉬 첨가한 시편의 경우 압축강도 87.5 kgf/$cm^2$로 가장 우수 하였으며 인공골재로의 이용이 가능함을 알 수가 있다.

• Journal of Biosystems Engineering
• /
• 제27권4호
• /
• pp.283-292
• /
• 2002

Mechanical and physical properties of various parts of jujube (Zizyphus jojoba Miller) such as fruits, leaves, secondary branches, and leafy stems were measured and analyzed. The physical dimensions of the fruits were measured using a digital caliper, and the detachment force of the fruit and leafy stems was measured using a force gauge. The physical characteristics of the secondary branches such as the modulus of elasticity and the torsional rigidity were tested using a universal testing machine (UTM). The physical characteristics of leafy stems such as length and weight were also measured using a digital caliper and a digital scale, respectively. The detachment force of leafy stems and the area of the leaf also measured. The terminal velocities of the jujube fruits, leaves, and leafy stems were measured using a custom made terminal velocity experiment system. Diameter of the major and minor axis of the jujube fruit, weight of the fruit, and detachment force of the fruit stem was average of 32.02 mm, 23.92 mm. 10.0 ${\times}$ 10$\^$6/ ㎥, 8.99 g, and 5.43 N. respectively. The detachment forces of the jujube fruits increased and the force-to-weight ratio of the jujube fruits decreased as the weight of the jujube fruits increased. The modulus of elasticity of the secondary branches of the jujube was average of 7.01 ${\times}$ 10$\^$8/ N/㎡ and decreased as diameter of the secondary branches increased. The average torsional rigidity of the secondary jujube branches was 5.2 ${\times}$ 10$\^$-/ N/㎡, and the torsional rigidity decreased as the secondary branch diameter increased. The distribution of the torsional rigidity data associated with the diameter of the branches, however. widely scattered and it was difficult to find any relationship between the diameter of the branches and the torsional rigidity of tile branches. The weight of the leafy stems, number of loaves attached to the leafy stems, diameter of the stem side of the leafy stems, diameter of the leafy stem end was average or 0.7 g, 6.6 ea, 12.2 cm, 4.5 mm, and 2.7 mm, respectively. The major and minor axis of the .jujube loaves, area of leaves, weight of the leaves. and detachment force of the leaves was average of 5.7 cm, 3.3 cm, 12.98 cm$^2$, 0.20 g, and 4.39 N, respectively. The terminal velocity of the .jujube fruits increased as the weight of the fruits increased. The terminal velocity of the leafy stems, however, did not show a relationship with the weight of the leafy stems and the number of leaves attached to the leafy stem. The terminal velocity, however, slightly increased as the length of the leafy stems increased.