• Electrical & Electronic Materials
• /
• v.10 no.9
• /
• pp.889-894
• /
• 1997

A miniaturized wind-mill type ultrasonic motor which has diameter in 12.7 mm and thickness in 2.0mm using PMN-PZT piezoelectric ceramics was fabricated. The wind-mill type ultrasonic motors has only three plate and of two wind-mill shape slotted metal endcaps a rotor whose end is hollowed out so that its periphery fits with the shape of the stator and a bearing to guide the rotor. A Finite Element Analysis was carried out to obtain the endcaps behavior under a radial displacement change of piezoelectric disk and to optimize the structure of the number of slots. Increasing the applied voltage the revolution speed of ultrasonic motors was increased. The maximum speed of 700 rpm and the maximum torque of 0.22 nN·m of the wind-mill type ultrasonic motors were obtained.

• Journal of the Korean Wood Science and Technology
• /
• v.36 no.1
• /
• pp.69-78
• /
• 2008

Shearing strength test in tension type was investigated to determine the shear resistance of bolt and drift-pin connection of domestic larix glulam. The specimen was connected with bolt and drift-pin in the inserted plate type, and only bolt in the side plate type. The diameter of bolt and drift-pin used in the experiment are 12, 16 and 20 mm. The hole of bolt was drilled at the end-distance 5 d and 7 d. Tension load was loaded in the direction parallel to grain. The shear resistance was evaluated according to end-distance through this, the yield load was compared with the experimental yield load, using Larsen's formula. The prototype design strength is based on the yield load of end-distance 7 d and the reduction factor of end-distance 5 d was calculated. The results were as follows. 1. The average of maximum load of drift-pin connection was higher by 3~30% at the inserted type than at bolt connection with increasing diameter. In bolt connection, the average of maximum load of the side type was 1.54~2.07 times higher than that of the inserted type. In the same diameter, the average of maximum load of end-distance 7 d was higher by 8~44% than that of 5 d. 2. The bearing stress was 1.16~1.41 times higher at the inserted connection than at drift-pin connection, and 1.37~1.86 times higher at 7 d than at 5 d. Also, when the slenderness ratio was below 7.5 at drift-pin connection and below 6.0 at inserted connection, the lateral capacity was good. 3. The ratio of the experimental yield load and the predicted yield load calculated by Larsen's formula proposed by Larsen was 0.80~1.10 at inserted connection, and 0.75~1.46 at side connection. 4. When the inserted bolt connection was based on the yield load of end-distance 7 d, the reduction factor was 0.89 at 12 mm connection, 0.93 at 16 mm and 0.85 at 20 mm. The reduction factor was 0.89 at 12 mm the inserted drift-pin connection, 0.93 at 16 mm, 0.93 at 20 mm. The reduction factor was 0.79 at the side connection of the 12 mm bolt connection and 0.80 at 16 mm.

• Journal of Plant Biology
• /
• v.36 no.4
• /
• pp.345-355
• /
• 1993

Anatomical study of the secondary xylem in Araliaceous plants, induding 7 genera and 11 species grown in Korea, was carried out to elucidate the relationship among genera in the family. Wood of Hedera has difbse porous and shows ulmiform pattern of angular vessels, simple perforation plate, and alternate pitting. In addition, its ray is homogeneous type II with only procumbent ray cell. Ring porous wood of Dendropanax shows ulmiform of angular vessels, simple perforation plate, alternate pitting, and heterogeneous type II ray, which has sometimes horizontal secretory cavity. Fatsia has diffuse porous wood, which shows ulmiform of angular vessels, scalariform perforation plate (3-9 bars), scalariform pitting, spiral thickening in the lateral wall of vessel, and heterogeneous type II ray with sheath cells. Kalopanax has ring porous wood, which shows ulmiform of circular vessels, simple perforation plate and alternate pitting, and heterogeneous type II ray. While K pictum appears tylose with septum, K pictum var. maximowczii appears tylose without septum. Echinopanax shows ring porous wood, ulmiform of angular vessels, simple perforation plate, scalariform pitting, and tylose with septum. And the ray of Echinopanax is paedomorphic type I composed of only upright cells. Acanthopanax genus is composed of diffuse porous wood, ulmiform of angular vessels, simple perforation plate and alternate pitting. In this genus, A. sessiliflorus has heterogeneous type II ray, apotracheal axial parenchyma and tylose with septum. A. senticosus appears paedomorphic type I with only upright cells, and tylose with septum. A. koreanum and A. sieboldianum have heterogeneous type II ray but have not tylose. Aralia is composed of ring porous wood, ulmiform of circular vessels, simple perforation plate, alternate pitting, heterogeneous type II ray, and tylose contained both septum and reticulate. On the basis of arrangement, shape, length and diameter of vessel element, the angle of end wall to vessel axis, and ray type, the line of specialization in these genera is as follow: from Fatsia, the most primitive, to the most highly specialized Aralia, throughout Hedera, Acanthopanax, Echinopanax, Dendropanax, and Kalopanax by turns. turns.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.12
• /
• pp.2070-2077
• /
• 2001

An experimental investigation of the effect of composite patching repair was conducted to characterize the fatigue crack growth behavior in thick A16061-T6 (6mm) panels with single bonded patch by fiber reinforced composite patch. Four patch lengths and no patch plate were examined. An analytical procedure, involving three-dimensional finite element method having three layers to model cracked aluminum plate, epoxy by adhesive and composite Patch, is calculated the stress intensity factors. From the calculated stress intensity factors, the fatigue crack growth rates are obtained. At the single patching type, different fatigue crack growth ratios through the palate thickness were investigated by using the experimental and analytical results. The results demonstrated that there was a definite variation in fatigue life depending on the size of composite patch. While crack reached the patch end, retardation of crack growth was also revealed in the bonded repair.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.663-668
• /
• 2008

This study was carried out solar heating system design for district heating and it's the performance analysis by experiment. This experimental system was installed in Bundang district heating area in the end of 2006. The flat plate and vacuum tube solar collector are combined in one system. So district heating water is heated first by flat plate solar collector and than by vacuum tube solar collector. This solar heating system has not a solar buffer tank and is operating with variable flow rate to obtain a setting temperature of $90{\sim}95^{\circ}C$. As a result, the daily solar thermal collection efficiency is about 30 to 40% for the plate type and 50 to 55% for the vacuum tube solar collector. It varied especially depend on the weather condition like as solar radiation and ambient temperature. This variable flow rate system can be also reduced much pumping power more than 50%.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.05a
• /
• pp.220-223
• /
• 2008

Large curved plate blocks are widely used to construct hull structure in shipbuilding industry. Most curved plates are manufactured by using manual method called as line heating that use deformation caused by residual stress after local heating along a line which is perpendicular to the curvature direction. However, its working environment is poor and its formability is totally dependent on an experienced technician. In view of that, multi-point dieless forming (MDF) technology that use reconfigurable punch arrays instead of one piece die is proposed in this study. The MDF process is based on a concept of equivalent die surface made by numbers of punches which has round tip at the end of it. In this study, numerical simulation for common curvature type such as saddle shape was carried out. In addition, experiments in the plate forming process were also conducted to compare with the numerical results in view of final configuration. Consequently, it was noted that the proposed dieless forming method has considerable feasibility to substitute the new process for conventional manual method.

• Steel and Composite Structures
• /
• v.18 no.2
• /
• pp.357-374
• /
• 2015

Orthotropic decks composed of deck plate, ribs, cross beams and wearing surface are frequently used in industry to span long distances due to their light structures and load carrying capacities. As a result they are broadly preferred in industry and there are a lot of bridges of this type exist in the world. Nevertheless, some of them cannot sustain the anticipated service life and damages in form of cracks develop in steel components and wearing surface. Main reason to these damages is seen as the repetitive wheel loads, namely the fatigue loading. Solutions to this problem could be divided into two categories: qualitative and quantitative. Qualitative solutions may be new design methodologies or innovative materials, whereas quantitative solution should be arranging dimensions of deck structure in order to resist wheel loads till the end of service life. Wearing surface on deck plate plays a very important role to avoid or mitigate these damages, since it disperses the load coming on deck structure and increases the bending stiffness of deck plate by forming a composite structure together with it. In this study the effect of Elastic moduli, Poisson ratio and thickness of wearing surface on the stresses emerged in steel deck and wearing surface itself is investigated using a FE-model developed to analyze orthotropic steel bridges.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.11
• /
• pp.520-526
• /
• 2019

I-type girders are widely applied as very economical sections in plate girder bridges. There has been research on developing composite laminated panels, curved plates reinforced with closed-end ribs, and new forms of ribs and compression flanges for steel box girders. However, there is a limitation in analyzing the exact cause of local buckling caused by an I-type girder's webs. Therefore, an I-type girder's web was modeled using the finite element analysis program LUSAS 17.0 before and after reinforcement. We checked for the minimum thickness criteria presented in the Korea highway bridge design code, and the cause of buckling after performing a linear elastic buckling analysis of dead and live loads was analyzed. Before reinforcement, an eigenvalue (λ₁) at the 1st mode was 0.7025, the critical buckling load was smaller than the applied load, and there is a buckling. After reinforcement, when applying vertical and horizontal stiffeners to the web part of the girder at support, a Nodal line was formed, the eigenvalue was 1.5272, and buckling stability was secured. To improve buckling trace of the girder at the support, an additional plate was applied to the web at the support to ensure visual and structural safety, but buckling occurs at center of web. The eigenvalue (λ₁) was 3.5299, and this method is efficient for reinforcing the web of the support.

• Industry Promotion Research
• /
• v.4 no.1
• /
• pp.11-20
• /
• 2019

This study relates to a fixing device for gas piping installed in a building such as an apartment or a building. The gas piping is fixed to the inside of the housing so as to buffer the gas piping in all directions, thereby relieving vibration caused by an earthquake or an impact, Disclosed is an earthquake-proof fixing device for a gas pipeline that can minimize damages caused by damage to an earthquake and a gas pipeline by preventing damage and breakage. An apparatus for fixing a gas pipe to a bracket provided on a wall or a wall of a building, the apparatus comprising: a housing coupled to a wall or a bracket and coupled to the inside of the housing; a gas pipe penetrating through the housing to fix the gas pipe; The first plate spring includes a first plate spring formed with a plurality of concave-convex portions that are elastically supported in four directions. The first plate spring is screwed to the front surface or the rear surface of the housing. The lower plate is coupled to one end and the other end, And a pair of first adjusting screws for adjusting the elastic force of the spring. Through this study, damage and damage of gas piping due to earthquake or impact can be minimized.

• Journal of Korean Society of Steel Construction
• /
• v.21 no.1
• /
• pp.45-53
• /
• 2009

More than 40% of railway bridges on the conventional lines in Korea consist of track-on-steel plate girder (TOSPG) bridges. This type of bridge is typically designed without considering seismic loadings, as most of them were built before 1970. The seismic performance of this particular type of bridge could be upgraded through various seismic retrofit schemes, and seismic risk assessment could play a key role in decision-making on the level of the seismic retrofit. This study performed a seismic risk assessment of TOSPG bridges in Korea. The seismic damage of several crucial components of TOSPG bridges--fixed bearings, free bearings, and piers--were probabilistically estimated, and their seismic fragility curves were developed. The probability that the components would exceed their predefined limit states was also calculated by combining the fragility curves and the seismic hazard function. The analysis showed that the piers of TOSPG bridges, which are made of plain concrete without rebars, have relatively low risk against seismic loadings in Korea. This is because the mass of the superstructures of TOSPG bridges is relatively small, and hence, the seismic loading being transferred to the piers is minimal. The line-type bearings typically used for TOSPG bridges, however, are exposed to a degree of seismic risk. Among the bearings, the probability of the free-end bearings and the fixed-end bearings exceeding the slight damage state in 50 years was found to be 12.78% and 4.23%, respectively. The gap between these probability values lessened towards more serious damage states. This study could effectively provide an engineering background for decision-making activities on the seismic retrofit of railway bridges.