• The Journal of Korean Academy of Prosthodontics
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• v.40 no.6
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• pp.545-559
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• 2002

There has been increasing use of IPS Empress $2^{(R)}$ owing to easy fabrication method, high esthetics similar to natural teeth, good marginal accuracy, and sufficient fracture strength. However, in clinical application, although a luting agent and the tooth cementation bonding procedure influence the marginal accuracy and fracture strength restoration, there has been a controversy in the selection of proper luting agent. This study was to measure the marginal fidelites and fracture strength of IPS Empress crowns according to three cement types, Protec $cem^{(R)}$, Variolink $II^{(R)}$ and Panavia $21^{(R)}$. After construction of 12 experimental dies for each group, IPS Empress $2^{(R)}$ crowns were fabricated and luted the metal master die prepartion of the maxillary right premolar. Marginal gaps before cementation and after cementation were measured. Buccal incline on the functional cusp of specimens were loaded until the catastrophic failure and fracture strength was measured. The results of this study were as follows: 1. The range of gap was $34.04{\pm}4.84{\mu}m$ before cementation and $37.88{\pm}5.00{\mu}m$ after cementation, which showed significant difference by paired t-test (p<0.05). The difference in the results from marginal accuracy according to measuring point proved to be not statistically significant by two-way ANOVA test (p>0.05). 2. The difference in the results from marginal accuracy according to three cement types Proved that The Variolink $II^{(R)}$ cement group had the least gap, $35.43{\pm}5.03{\mu}m$, and showed superior marginal accuracy while there existed statistic significance in Protec $cem^{(R)}$ cement group, $39.06{\pm}4.41{\mu}m$ or Panavia $21^{(R)}$ cement group, $39.16{\pm}4.39{\mu}m$ by two-way ANOVA test & multiple range test (p<0.05). 3. The difference in the results from fractures strength testing according to three cement type groups proved to be statistically significant (p<0.05). The Variolink $II^{(R)}$ cement group shows highest fracture strength of $1257.33{\pm}226.77N$, Panavia $21^{(R)}$ cement group has $1098.08{\pm}138.45N$, and Protec $cem^{(R)}$ cement group represents the lowest fracture strength of $926.75{\pm}115.75N$. 4. Three different cement groups of different components showed acceptable marginal fidelity and fracture strength. It is concluded that IPS Empress $2^{(R)}$ crowns luted using Variolink $II^{(R)}$ cement group had stronger fracture strength and smaller marginal gap than the other cement groups. Although Variolink $II^{(R)}$ resin cement seemed acceptable to clinical applications in IPS Empress $2^{(R)}$ system, the IPS Empress $2^{(R)}$ system still requires long-term research due to the lack of data in clinical applications.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.2
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• pp.51-58
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• 2017

We investigated the efficiency of natural zeolite with different cation exchange capacity (CEC) as capping material for the remediation of marine sediments contaminated with heavy metals. Three different zeolite with high CEC (HCzeo, 163.74 cmolc/kg), medium CEC (MCzeo, 127.20 cmolc/kg), and low CEC (LCzeo, 70.62 cmolc/kg) were used. The surface area of the zeolite was in decreasing order: HCzeo ($59.43m^2/g$) > MCzeo ($52.10m^2/g$) > LCzeo ($10.12m^2/g$). The results of mineralogical composition obtained from X-ray diffraction (XRD) show that LCzeo was mainly composed of quartz and albite. In the XRD result of MCzeo and HCzeo, the peaks of clinoptilolite, heulandite, and mordenite were also observed along with that of quartz and albite. Sorption equilibrium onto the HCzeo, MCzeo, and LCzeo was reached in 6 h at initial concentration of 10 mg/L and 100 mg/L. Higher adsorption of Cd and Zn onto the zeolite with higher CEC were achieved but adsorption of Cu and Ni were not dependent on the CEC of zeolite. It can be concluded that the zeolite with high cation exchange ability is recommended for the contaminated sediments with Cd and Zn but the inexpensive zeolite with low CEC for Cu and Ni.

• Journal of the Korean Orthopaedic Association
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• v.53 no.6
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• pp.466-477
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• 2018

Orthopaedics is an area where 3-dimensional (3D) printing technology is most likely to be utilized because it has been used to treat a range of diseases of the whole body. For arthritis, spinal diseases, trauma, deformities, and tumors, 3D printing can be used in the form of anatomical models, surgical guides, metal implants, bio-ceramic body reconstruction, and orthosis. In particular, in orthopaedic oncology, patients have a wide variety of tumor locations, but limited options for the limb salvage surgery have resulted in many complications. Currently, 3D printing personalized implants can be fabricated easily in a short time, and it is anticipated that all bone tumors in various surgical sites will be reconstructed properly. An improvement of 3D printing technology in the healthcare field requires close cooperation with many professionals in the design, printing, and validation processes. The government, which has determined that it can promote the development of 3D printing-related industries in other fields by leading the use of 3D printing in the medical field, is also actively supporting with an emphasis on promotion rather than regulation. In this review, the experience of using 3D printing technology for bone tumor surgery was shared, expecting orthopaedic surgeons to lead 3D printing in the medical field.

• Korean Journal of Materials Research
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• v.11 no.5
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• pp.367-371
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• 2001

In this paper, theS $r_2$(T $a_{1-x}$ , N $b_{x}$)$_2$ $O_{7}$(STNO) films among ferroelectric materials having a low dielectric constant for metal-ferroelectric-semiconductor field effect transistor(MFS-FET) were discussed. The STNO thin films were deposited on p-type Si(100) at room temperature by co-sputtering with S $r_2$N $b_2$ $O_{7(SNO)}$ ceramic target and T $a_2$ $O_{5}$ ceramic target. The composition of STNO thin films was varied by adjusting the power ratios of SNO target and T $a_2$ $O_{5}$ target. The STNO films were annealed at 8$50^{\circ}C$, 90$0^{\circ}C$ and 9$50^{\circ}C$ temperature in oxygen ambient for 1 hour. The value of x has significantly influenced the structure and electrical properties of the STNO films. In the case of x= 0.4, the crystallinity of the STNO films annealed at 9$50^{\circ}C$ was observed well and the memory windows of the Pt/STNO/Si structure were 0.5-8.3 V at applied voltage of 3-9 V and leakage current density was 7.9$\times$10$_{08}$A/$\textrm{cm}^2$ at applied voltage of -5V.of -5V.V.V.

• The korean journal of orthodontics
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• v.41 no.6
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• pp.399-410
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• 2011

Objective: The purpose of this study was to evaluate the difference in frictional resistance among metal, ceramic, self-ligation brackets and coated or non-coated Ni-Ti archwires at various bracket-archwire angulations during the sliding movement of an orthodontic archwire, using an orthodontic sliding simulation device. Methods: Four types of bracket (Micro-arch Perpect Clear2 Clippy-C and Damon3 and 5 types of orthodontic archwire (0.014", 0.016", and 0.016" ${\times}$ 0.022" inch coated Ni-Ti, and 0.016" and 0.016" ${\times}$ 0.022" inch Ni-Ti) were used. Further, the bracket- archwire angles were set at 4 different angulations: $0^{\circ}$, $3^{\circ}$, $6^{\circ}$, and $9^{\circ}$. Results: The frictions from all the experimental groups were found to be significantly increased in order of self-ligation brackets, Micro-arch and Perpect Clear2 ($p$ < 0.001). The presence of a coat had no effect on the friction of the same sized archwires at $0^{\circ}$ and $3^{\circ}$ bracket-archwire angles ($p$ < 0.001). Coated archwires had significantly higher frictions than the same sized non-coated archwires at $6^{\circ}$ and $9^{\circ}$ bracket-archwire angles ($p$ < 0.001). The frictions increased significantly as the bracket-archwire angles were increased ($p$ < 0.001). Conclusions: The use of self-ligation brackets will be beneficial in clinical situations where a low frictional force is required. Further, in cases where crowding is not severe, the use of coated archwires should not cause problems. However, more additional explanation is required considering the fact that the damage of coated archwire and exposure of the metal portion in case of binding and notching and the effects of saliva were not taken into account.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.83-89
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• 2020

For the past few decades, as part of efforts to protect the environment where fossil fuels, which have been a key energy resource for mankind, are becoming increasingly depleted and pollution due to industrial development, ecofriendly secondary batteries, hydrogen generating energy devices, energy storage systems, and many other new energy technologies are being developed. Among them, the lithium-ion battery (LIB) is considered to be a next-generation energy device suitable for application as a large-capacity battery and capable of industrial application due to its high energy density and long lifespan. However, considering the growing battery market such as eco-friendly electric vehicles and drones, it is expected that a large amount of battery waste will spill out from some point due to the end of life. In order to prepare for this situation, development of a process for recovering lithium and various valuable metals from waste batteries is required, and at the same time, a plan to recycle them is socially required. In this study, we introduce a nanoscale pattern transfer printing (NTP) process of Li2CO3, a representative anode material for lithium ion batteries, one of the strategic materials for recycling waste batteries. First, Li2CO3 powder was formed by pressing in a vacuum, and a 3-inch sputter target for very pure Li2CO3 thin film deposition was successfully produced through high-temperature sintering. The target was mounted on a sputtering device, and a well-ordered Li2CO3 line pattern with a width of 250 nm was successfully obtained on the Si substrate using the NTP process. In addition, based on the nTP method, the periodic Li2CO3 line patterns were formed on the surfaces of metal, glass, flexible polymer substrates, and even curved goggles. These results are expected to be applied to the thin films of various functional materials used in battery devices in the future, and is also expected to be particularly helpful in improving the performance of lithium-ion battery devices on various substrates.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.3
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• pp.328-334
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• 2009

Statement of problem: Pier abutments act as a Class I fulcrum lever system when the teeth are incorporated in a fixed partial denture with rigid connectors. Therefore non-rigid connector incorporated into the fixed partial denture might reduce the stresses created by the leverage. Purpose: The purpose of this study was to evaluate, by means of finite element method, the effects of non-rigid connectors and supporting alveolar bone level on stress distribution for fixed partial dentures with pier abutments. Material and methods: A 2-dimensional finite element model simulating a 5-unit metal ceramic fixed partial denture with a pier abutment with rigid or non-rigid designs, the connector was located at the distal region of the second premolar, was developed. In the model, the lower canine, second premolar, and second molar served as abutments. Four types of alveolar bone condition were employed. One was normal bone condition and others were supporting bone reduced 20% height at one abutment. Two different loading conditions, each 150 N on 1st premolar and 1st molar and 300N on 1st molar, were used. Results: Two types of FPD were displaced apically. The amount of displacement decreased in an almost linear slope away from the loaded point. Non-rigid design tended to cause the higher stresses in supporting bone of premolar and molar abutments and the lower stresses in that of canine than rigid design. Alveolar bone loss increased the stresses in supporting bone of corresponding abutment. Conclusion: Careful evaluation of the retentive capacity of retainers and the periodontal condition of abutments may be required for the prosthetic design of fixed partial denture with a pier abutment.

• Journal of the Korean Electrochemical Society
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• v.18 no.3
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• pp.121-129
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• 2015

The platinum anode for the electrolytic reduction process is generally surrounded by a nonporous ceramic shroud with an open bottom to offer a path for $O_2$ gas produced on the anode surface and prevent the corrosion of the electrolytic reducer. However, the $O^{2-}$ ions generated from the cathode are transported only in a limited fashion through the open bottom of the anode shroud because the nonporous shroud hinders the transport of the $O^{2-}$ ions to the anode surface, which leads to a decrease in the current density and an increase in the operation time of the process. In the present study, we demonstrate the electrolytic reduction of 1 kg-uranium oxide ($UO_2$) using the porous shroud to investigate its long-term stability. The $UO_2$ with the size of 1~4mm and the density of $10.30{\sim}10.41g/cm^3$ was used for the cathode. The platinum and 5-layer STS mesh were used for the anode and its shroud, respectively. After the termination of the electrolytic reduction run in 1.5 wt.% $Li_2O-LiCl$ molten salt, it was revealed that the U metal was successfully converted from the $UO_2$ and the anode and its shroud were used without any significant damage.