• The korean journal of orthodontics
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• v.48 no.2
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• pp.107-112
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• 2018

Objective: The aim of this study was to examine the properties of fiber-reinforced composite and stainless steel twisted retainers for orthodontic retention. Methods: Three different span lengths (5.0, 8.0, and 14.0 mm) of fiber-reinforced composite were investigated. The three fiber-reinforced composite retainer groups were subdivided according to the storage condition (dry and wet), resulting in a total of six groups. Each stainless steel and fiber-reinforced composite group was comprised of six specimens. The three-point bending flexural test was conducted using a universal testing machine. ANOVA was used to assess differences in the maximum load and maximum stress according to the span length, material, and storage condition. Post-hoc comparisons were performed if necessary. Results: The maximum stress and maximum load were significantly (p < 0.001) associated with the span length, material, and storage condition. The significant interaction between the material and span length (p < 0.001) indicated the differential effects of the material for each span length on the maximum stress and maximum load, with the difference between materials being the highest for the maximum span length. Conclusions: Our findings suggest that fiber-reinforced composite retainers may be an effective alternative for orthodontic retention in patients with esthetic concerns or allergy to conventional stainless steel wires.

• Journal of the Korean Geosynthetics Society
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• v.15 no.1
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• pp.11-19
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• 2016

This paper presents the results of a scale model test to the effect of heat exchanger drainage method in retaining wall of weathered granite soil. Purpose to rise in the temperature of the heat wires inside the weathered granite soil is preventing the collapse of the retaining wall and drainage smoothly moved to the drainage layer. Especially using a spray gun to simulate the rainfall since the rainfall drainage work is important for the rainfall effect on soil, find the difference about displacement of the retaining wall, change of volume water content, drainage, earth pressure and change in the strain of the geosynthetic was effected to heat exchanger within the soil. The result from applying the heat exchanger method decreased the earth pressure and displacement of the wall and increased drainage of water.

• Progress in Superconductivity and Cryogenics
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• v.18 no.4
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• pp.21-24
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• 2016

The mechanical properties of REBCO coated conductor (CC) wires under uniaxial tension are largely determined by the thick component layers in the architecture, namely, the substrate and the stabilizer or even the reinforcement layer. Depending on device applications of the CC tapes, it is necessary to reinforce thin metallic foils externally to one-side or both sides of the CC tapes. Due to the external reinforcement of brass foils, it was found that this could increase the reversible strain limit from the Cu-stabilized CC tapes. In this study, the effects of differently hardened brass foil laminate on the electromechanical property of CC tapes were investigated under uniaxial tension loading. The tensile strain dependence of the critical current ($I_c$) was measured at 77 K and self-field. Depending on whether the $I_c$ of CC tapes were measured during loading or after unloading, a reversible strain (or stress) limit could be determined, respectively. The both-sides of the Cu-stabilized CC tapes were laminated with brass foils with different hardness, namely 1/4H, 1H and EH. From the obtained results, it showed that the yield strength of the brass laminated CC tapes with EH brass foil laminate was comparable to the one of the Cu-stabilized CC tape due to its large yield strength even though its large volume fraction. It was found that the brass foil with different hardness was mainly sensitive on the stress dependence of $I_c$, but not on the strain sensitivity due to the residual strain induced in the laminated CC tapes during unloading.

• International Journal of Concrete Structures and Materials
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• v.9 no.3
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• pp.369-379
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• 2015

Friction in a post-tensioning system has a significant effect on the distribution of the prestressing force of tendons in prestressed concrete structures. However, attempts to derive friction coefficients using conventional electrical resistance strain gauges do not usually lead to reliable results, mainly due to the damage of sensors and lead wires during the insertion of strands into the sheath and during tensioning. In order to overcome these drawbacks of the existing measurement system, the Smart Strand was developed in this study to accurately measure the strain and prestressing force along the strand. In the Smart Strand, the core wire of a 7-wire strand is replaced with carbon fiber reinforced polymer in which the fiber Bragg grating sensors are embedded. As one of the applications of the Smart Strand, friction coefficients were evaluated using a full-scale test of a 20 m long beam. The test variables were the curvature, diameter, and filling ratio of the sheath. The analysis results showed the average wobble and curvature friction coefficients of 0.0038/m and 0.21/radian, respectively, which correspond to the middle of the range specified in ACI 318-08 in the U.S. and Structural Concrete Design Code in Korea. Also, the accuracy of the coefficients was improved by reducing the effective range specified in these codes by 27-34 %. This study shows the wide range of applicability of the developed Smart Strand system.

• Journal of Korean Foot and Ankle Society
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• v.12 no.2
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• pp.168-173
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• 2008

Purpose: To evaluate the results of treatments by percutaneous Acutrak screw fixation for intra-articular joint depression type fracture of calcaneus. Materials and Methods: Thirteen cases with intra-articular joint depression type fracture of calcaneus, from September 2004 to March 2006, were reviewed. There were 9 males and 4 females with 52.5 years old mean age (range: $31{\sim}74$ years old). The average follow-up period was 18 months (range: $8{\sim}32$ months). Steinmann pins and Freers were used for closed reduction. After closed reduction, Acutrak screws and K-wires were inserted. The patients were evaluated with Creighton-Nebraska health foundation assessment sheet for calcaneal fracture, the extent of recovery of Bohler angle, fragment size, and state of subtalar joint. Results: Clinical results according to Creighton-Nebraska health foundation assessment sheet for calcaneal fracture were excellent in 6 cases (46%), good in 4 cases (30%), fair in 2 cases (15%), and poor in 1 case (7%). Average preoperative Bohler angle was $7.6^{\circ}$ (range: $2^{\circ}{\sim}13^{\circ}$). Average postoperative Bohler angle was $24.4^{\circ}$ (range: $4^{\circ}{\sim}33^{\circ}$). There were no soft tissue complications. There were one mild subtalar arthritis and one moderate subtalar arthritis. Conclusion: We think that closed reduction and percutaneous Acutrak screw fixation with or without K-wire is a good option for joint depression type fracture of calcaneus.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.187-190
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• 2006

In the present study, effects of tree-stream turbulence and surface trip wire on the flow past a sphere at $Re\;=\;0.4\;{\times}\;10^5\;{\sim}\;2.8\;{\times}\;10^5$ are investigated through wind tunnel experiments. Various types of grids are installed upstream of the sphere in order to change the tree-stream turbulence intensity. In the case of surface trip wire, 0.5mm and 2mm trip wires are attached from $20^{\circ}\;{\sim}\;90^{\circ}$ at $10^{\circ}$ interval along the streamwise direction. To investigate the flow around a sphere, drag measurement using a load cell, surface-pressure measurement, surface visualization using oil-flow pattern and near-wall velocity measurement using an I-type hot-wire probe are conducted. In the variation of free-stream turbulence, the critical Reynolds number decreases and drag crisis occurs earlier with increasing turbulence intensity. With increasing Reynolds number, the laminar separation point moves downstream, but the reattachment point after laminar separation and the main separation point are fixed, resulting in constant drag coefficient at each free-stream turbulence intensity. At the supercritical regime, as Reynolds number is further increased, the separation bubble is regressed but the reattachment and the main separation points are fixed. In the case of surface trip wire directly disturbing the boundary layer flow, the critical Reynolds number decreases further with trip wire located more downstream. However, the drag coefficient after drag crisis remains constant irrespective of the trip location.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.6
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• pp.81-90
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• 2004

For deep submicron (DSM) very large scale integrated circuits (VLSI), it is well known that interconnects have become the dominant factor in determining the overall circuit performance. Buffer insertion is an effective technique of interconnect optimization. When a net has an excessive propagation delay, one or more buffers can be inserted to reduce the delay. Buffers also reduce the crosstalk between neighboring wires. While many conventional methods insert buffers net by net. we have developed new techniques in which buffer locations are simultaneously optimized for all nets. This is to avoid the difficulties in finding the right ordering of nets for buffer insertion. since several nets may compete for a buffer location. We also study buffer insertion with multiple fan-out nets to optimize critical path delay. Elmore delay model is used for delay calculation and the number of buffers for each net is determined to optimize the delay.

• Journal of the Korean Home Economics Association
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• v.45 no.4
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• pp.43-51
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• 2007

This study analyzed the knit wear trend, which has gained attention as a sensuous and luxury item, through collection magazines, and used the technique of hand-knit to produce and present the knit wear that was designed based on the study results. Accordingly, the purpose of this study is to raise awareness of the expansion of hand knit's new expression techniques and expression areas and to verify its possibility as a higher value-added product. The trends of hand-knit wear resulted from the analysis of collections divided into the following four groups, and the knit designs were also grouped accordingly: First was "The design using object." The trend survey showed the results that the form of drops or flowers was often used as a factor of object. Accordingly, as for the study design, the drop-knitting technique, which is one of the pattern knitting techniques, was used to present a design that employed drops as the object. Second was "The design matched with woven material." It is a way to emphasize aesthetic formativeness and at the same time to activate the area of knit design by matching woven material, which is different from knit in texture, with knit. This study presented a design that tried to combine knit texture and woven material by connecting denim material with various textures and colors. Third was "The design to express see-through." A sense of showing through knit wear was expressed through changes in the type of thread or knitting technique. In this study, the sense of see-through was expressed using piano wires and wool threads and through changes in the thickness of needle. Fourth was "The design to emphasize coloring." It was analyzed that regarding the production of hand knit, the method of coloring expression was to express points, lines and sides or to create harmony by changing the material's color or texture to show particular objects or shapes. In this study, a jacket was designed using the method to express points, lines and sides by changing the material's color.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.2
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• pp.154-161
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• 1984

A modified technique of the transient hot wire method to measure the thermal conductivity of fluid has been described in this paper. The thermal conductivity of fluid can be obtained by acquiring wire temperature as a function of time. Multiplication of the inverse slope of the temperature versus logarithm of time by an instrumental constant gives the thermal conductivity. The constant voltage was applied to Wheatstone bridge circuit. The wire temperature can be measured as a function of time precisely with the aid of the data acquisition system composed of a microprocessor and an analog-digital converter. The thermal conductivity of the electrically conducting fluid has been measured with the insulated hot wire coated by electrically non-conducting material. The effect of the coated insulation layer on the thermal conductivity has been examined, in which it is confirmed that the thermal conductivity of electrically conducting liquid can be determined by the transient coated hot wire method. Thermal conductivities of methanol, carbontetrachrolide, Freon-22 and glycerin have been measured at room temperature in the pressure from 0.1MPa to 35.1MPa. The experiment has been performed to compare the data from the bare and the coated wires, and the results are satisfactory.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1281-1293
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• 2013

A sophisticated finite element model is illustrated to analyze the behavior of Prefabricated Parallel Wire Strand(PPWS) sockets for main cables of suspension bridges. An orthotropic model is proposed for the casting material by considering both effects of individual wires and a casting alloy, and the contact between surfaces of a socket and a casting alloy is idealized by using the Coulomb friction and the surface-based contact model. The proposed FE model is verified by comparing the strain distributions obtained from the tensile test and FE analysis. The mechanical behavior of a socket is investigated with respect to the variation of the frictional coefficient. The result shows that the friction between surfaces significantly diminishes the stress concentration of a socket and a casting alloy, and the normal stress from the design equation represents the averaged value of the upper and lower quartiles in the distribution of contact stresses between a socket and a casting alloy.