• Transactions of Materials Processing
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• v.23 no.8
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• pp.489-494
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• 2014

Micro forming is an appropriate process to manufacture very small metal parts which can be employed in the field of electronic devices or electrically controlled mechanical systems. The purpose of the current study was to investigate the influences of both blankholding force and blank diameter for the deep drawing of very small cups. It is essential to control the blankholding force because improper force can result in defects such as wrinkles in the flange or cracks in the corner of the drawn cups. In the current study blankholding force was controlled by springs connected to the blankholder of a press die. Exchangeable bushing dies with various die-corner radii were also used. To obtain the limit drawing ratio for each working condition several sizes of circular specimens were prepared using blanking tools. Beryllium copper(C1720) alloy sheet of $50{\mu}m$ thickness was chosen for the experiments. The maximum limit drawing ratio of 2.1 was achieved experimentally for the conditions of the blankholder force(BHF)=5.3kgf and Rd=0.3mm. Both thickness and hardness along the central section of drawn cups were measured and compared for different drawing conditions. It was found that the deviation of measured data in the thickness and hardness distribution increases with increasing blankholder force and blank diameter.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.3
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• pp.244-249
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• 2015

With the recent progress of digital technology, the computer guided surgery utilizing a guide template in the placement of implant has been actively performed, and the method employing the intraoral scanner at the implant prosthesis introduced. Fabrication method of the guide template can be largely classified into design-related rapid prototyping (RP) system and vector milling system, and each of the method has its own weakness in the clinical application despite of excellent accuracy. Thus, in this case study, a working model was fabricated by the wax RP technology using images acquired by CBCT and an intraoral scanner, and the metal bushing was picked up with orthodontic resin cast upon the wax model. Using this method, a surgical guide template was fabricated and used in surgery. From this, we could obtain a satisfactory outcome clinically in the implant placement and the fabrication of the final prostheses and thus report this case herein.

• Composites Research
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• v.23 no.3
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• pp.43-49
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• 2010

Basaltic fiber was prepared by continuous spinning process from Jeju Pyosun raw basalt materials. First, for confirming the melting characterization of basalt, basalt raw material put into Pt crucible and melted up to $1550^{\circ}C$ then quenched by dropping it into water. After quenching, the optimum fiber spinning conditions were investigated by measurement and analysis of XRD, TMA, high temperature viscosity, high temperature conductivity and high temperature microscope. The optimum spinning temperature and viscosity for preparation of continuous filament fiber were $1264^{\circ}C$ and $10^{2.8}$ poise at $1264^{\circ}C$, respectively. Properties of prepared spinning fiber were confirmed by tensile strength, FE-SEM, heat resisting test and others. The tensile strength of fiber prepared by spinning conditions of the bushing temperature $1240^{\circ}C$ and winder speed 4600rpm was 3660MPa.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1629-1631
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• 1998

Crosslinked polyethylene (XLPE) insulated cables are now widely used all over the world for extra-high voltage underground transmission systems. Prefabricated type (compression type) joint has developed in order to shorten the assembly time and lower the possibility of contamination at site by many companies in the world. For outdoor termination, to control the electric field distribution as uniform as possible, especially for the use of extra-high voltage system. much of products are adopting the oil-impregnated condensor cone type instead of electric field control element which uses the permitivity of it only (not capacitance). For Gas-immersed termination, dimension of outer insulation bushing was determined by IEC Publication 859. The highest voltage of underground power cable system is 345kV now, in Korea. We have much of experiences of the development of prefabricated type accessories for CV cable systems (154kV, 161kV, 230kV level). So it was possible to inspect the proto type of accessories for 345kV CV cable system and seems that the need time for the development of products is reduced.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.4
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• pp.255-263
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• 2014

In this paper, seismic fragility analysis of lightning arrester is performed using capacity spectrum method(CSM). Since seismic fragility analysis of structure with many structural members is required to calculate many inelastic responses for several tens or hundreds of ground motions, simple method such as CSM is more appropriate than response history analysis(RHA). In general, accuracy of seismic response evaluated by CSM is less than that by RHA. In order to increase accuracy of CSM, equivalent SDOF method and performance point calculation technique are applied to CSM. Seismic fragility method proposed by Shinozuka et al. is used. In order to evaluate site effect of ground motions on seismic fragility, 60 different site classification earthquakes are selected as input ground motions. From the seismic fragility curves of lightning arrester evaluated by CSM and RHA, it can be observed that the seismic fragility curves evaluated by CSM are very similar to those by RHA. Also, it can be observed that main seismic failure mode of lightning arrest is bushing breakage.

• Journal of Sensor Science and Technology
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• v.7 no.4
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• pp.293-299
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• 1998

An objective of this study is to develop a voltage measuring device that uses a gas-filled switch (GS) on 22.9 kV-y extra-high voltage distribution lines. The voltage measuring device proposed in this paper is a kind of capacitive divider which consists of a detecting electrode attached outside of the bushing of GS, an impedance matching circuit, and a voltage buffer. It can be easily installed in an established GS without changing the structure. For the calibration and application investigations, the voltage measuring device was set up in the 25.8 kV 400 A GS, and a step pulse generator having 5 ns rise time is used. As a result, it was found that the frequency bandwidth of the voltage measuring device ranges from 1.35 Hz to about 13 MHz. The error of voltage dividing ratio which is evaluated by the commercial frequency voltage of 60 Hz was less than 0.2%. In addition, voltage dividing ratio in the commercial frequency voltage and in a non-oscillating impulse voltage were compared, and their deviation were less than 0.7%.

• Journal of the Korean institute of surface engineering
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• v.54 no.5
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• pp.267-277
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• 2021

Nitriding layers developed during gaseous nitriding of AISI4115 steels for the application of steel bushing part were investigated. The compound layer thickness of about 10㎛, 0.3mm of case depth under the same conditions, and conventional nitriding, nitrocarburizing, and controlled nitriding were performed in three methods. In the controlled nitriding, K_N was controlled by measuring the hydrogen partial pressure. The nitrided samples were analyzed by micro Vickers hardness test, optical microscopy and scanning electron microscopy. The phases of compound layer were identified by X-ray diffraction and electron backscatter diffraction. The controlled nitriding specimen indicated the highest surface hardness of about 860 HV_0.1. The compound layer of the conventional nitriding and nitrocarburizing specimen was formed with about 46% porous layer and 𝜺 + 𝜸' phase, and about 13% porous layer and about 80% 𝜸' phase were formed on the controlled nitriding specimen. As a result of the Ball-on-disk wear test, the worn mass loss of ball performed on the surface of the controlled nitriding specimen was the largest. The controlled nitriding specimen had the highest surface hardness due to the lowest porous percentage of compound layer, which improved the wear resistance.

• Journal of the Korean Orthopaedic Association
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• v.55 no.3
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• pp.244-252
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• 2020

Purpose: Total femoral replacement (TFR) is an extreme form of limb salvage. Considering the rarity of this procedure, reports have focused on the complications and a proper indication is unclear. This study analyzed 36 patients with TFR who were asked the following: 1) prognostic factors related to survival in patients who underwent TFR with a tumoral cause; 2) overall implant and limb survival; 3) complications, functional outcome, and limb status for patients surviving for more than 3 years. Materials and Methods: According to the causes for TFR, 36 patients were categorized into three groups: extensive primary tumoral involvement (group 1, 15 cases), tumoral contamination by an inadvertent procedure or local recurrence (group 2, 16 cases), and salvage of a failed reconstruction (group 3, 5 cases). The factors that may affect the survival of patients included age, sex, cause of TFR, and tumor volume change after chemotherapy. Results: The overall five-year survival of the 36 patients was 31.5%±16.2%. The five-year survival of 31 patients with tumoral causes was 21.1%±15.6%. The five-year survival of 50.0%±31.0% in patients with a decreased tumor volume after chemotherapy was higher than that of increased tumor volume (p=0.02). The five-year survival of 12 cases with a wide margin was 41.7%±27.9%, whereas that of the marginal margin was 0.0%±0.0% (p=0.03). The ten-year overall implant survival of 36 patients was 85.9%±14.1%. The five-year revision-free survival was 16.6%±18.2%. At the final follow-up, 12 maintained tumor prosthesis, three underwent amputation (rotationplasty, 2; above knee amputation, 1), and the remaining one had knee fusion. Among 16 patients with a follow-up of more than three years, 14 patients underwent surgical intervention and two patients had conservative management. Complications included infection in 10 cases, local recurrences in two cases, and one case each of hip dislocation, bushing fracture, and femoral artery occlusion. Conclusion: Patients showing an increased tumor volume after chemotherapy and having an inadequate surgical margin showed a high chance of early death. In the long-term follow-up, TFR showed a high infection rate and the functional outcome was unsatisfactory. Nevertheless, this procedure is an inevitable option of limb preservation in selected patients.

• Smart Structures and Systems
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• v.26 no.5
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• pp.575-589
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• 2020

For vibration control of stay cables in cable-stayed bridges, viscous dampers are frequently used, and they are regularly installed between the cable and the bridge deck. In practice, neoprene rubber bushings (or of other types) are also widely installed inside the cable guide pipe, mainly for reducing the bending stresses of the cable near its anchorages. Therefore, it is important to understand the effect of the bushings on the performance of the external damper. Besides, for long cables, external dampers installed at a single position near a cable end can no longer provide enough damping due to the sag effect and the limited installation distance. It is thus of interest to improve cable damping by additionally installing dampers inside the guide pipe. This paper hence studies the combined effects of an external damper and an internal damper (which can also model the bushings) on a stay cable. The internal damper is assumed to be a High Damping Rubber (HDR) damper, and the external damper is considered to be a viscous damper with intrinsic stiffness, and the cable sag is also considered. Both the cases when the two dampers are installed close to one cable end and respectively close to the two cable ends are studied. Asymptotic design formulas are derived for both cases considering that the dampers are close to the cable ends. It is shown that when the two dampers are placed close to different cable ends, their combined damping effects are approximately the sum of their separate contributions, regardless of small cable sag and damper intrinsic stiffness. When the two dampers are installed close to the same end, maximum damping that can be achieved by the external damper is generally degraded, regardless of properties of the HDR damper. Field tests on an existing cable-stayed bridge have further validated the influence of the internal damper on the performance of the external damper. The results suggest that the HDR is optimally placed in the guide pipe of the cable-pylon anchorage when installing viscous dampers at one position is insufficient. When an HDR damper or the bushing has to be installed near the external damper, their combined damping effects need to be evaluated using the presented methods.

• Journal of Korean society of Dental Hygiene
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• v.11 no.5
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• pp.659-670
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• 2011

Objectives : The purpose of this study was to examine the state of oral health care among special school personnels in an attempt to provide some information on the improvement of the oral health care of students with disabilities who would be under the first hand influence of school personnels. Methods : The subjects in this study were personnels who were selected by random selection in five different special schools located in the city of Jeonju, North Jeolla Province. A self-administered survey was conducted in person from July 5 to 14 after the purpose of this study was explained. Results : 1. Concerning their general characteristics, the level of oral health knowledge was high in the personnel whose career is 5 years more, and the younger personnels had a better oral health knowledge, and the men were more knowledgeable than the women. 2. As to oral health education experience, the rate of the respondents who ever received oral health education stood at 35.3 percent. In relation to the frequency of oral health education, the biggest group that accounted for 58.2 percent received that education once. As for the route of education, the largest group that represented 52.7 percent received that education at dental hospitals or clinics. In relation to satisfaction with oral health education, the greatest group that accounted for 38.5 percent were dissatisfied with that education. 3. As for an intention of receiving oral health education in the future, the biggest group that accounted for 60.9 percent intended to receive that education if they would have free time, and the largest group that represented 47.7 percent believed that oral health education should be conducted by dental hygienists. 4. Concerning their general characteristics, the level of oral health promotion behavior according to age in both bushing and supplies of oral health care was high in forties-1.89 point and 3.33 point, and that in regular visit to a dental clinic was the highest in twenties for 2.58 point, and that in dietary control was the highest in twenties for 2.59 point. 5. Their oral health knowledge had a significant positive correlation to their toothbrushing, regular dental clinic visit and dietary control that were the subfactors of oral health promotion behavior. 6. As for the impact of oral health promotion behavior on oral health knowledge, toothbrushing exerted the greatest influence on that(${\beta}$=0.306, p<0.001). Conclusions : Appropriate institutional measures should be taken to let dental hygienists who are expert in oral health care provide incremental oral health care for students and adults with disabilities in educational institutions and facilities for the disabled, and the development of oral health education programs is urgently required to offer systematic oral health education for not only students with disabilities but their teachers and guardians.