• Journal of Yeungnam Medical Science
• /
• v.13 no.1
• /
• pp.116-133
• /
• 1996

The biocompatibility of the titanium has been estabilished through various experimental studies such as cell culture toxicity test, pyrogen test, mutagen test and others. In order to confirm biocompatibility after fabrication of titanium and to clarify the difference between the bone reaction after insertion of the lathed titanium rods and the bone reaction after insertion of the finished and polished rods, both rods were implanted into the proximal femur of a rabbit. Histologic reactions in the bone were observed according to the ASTM standards at the intervals of 6 weeks, 12 weeks and 26 weeks after implantation. The result were as follows : In 6 weeks after implantation of lathed titanium rods, inflammatory reactions, such as minimal degree infiltration of polymorphonuclear leukocytes and lymphocytes were observed in all cases. This was thought to he caused by surgical trauma. However, inflammatory cell infiltration was not seen after implantation of polished and finished rods in all cases. The cellular infiltration and the histologic reaction of the hone after implantation of lathed group were significantly more pronounced than those after implantation of the finished group. In 12 weeks after implantation of lathed rods, two of four cases revealed a minimal degree of cellular infiltration. No inflammatory cell infiltration was demonstrated after implantation of the finished group. The cellular infiltration and histologic reaction seemed to be more pronounced in the lathed group, but they were not significant statistically. At 26 weeks after implantation of the lathed and finished group, there was no cellular infiltration in both groups. New bone formation was observed up 26 weeks, and no difference between lathed titanium rods and finished titanium rods were apparent. Mild bone necrosis was observed in 1 case out of 11 cases in which lathed titanium rods were implanted. Bone necrosis was not observed in the finished titanium rod group. Fibrosis was observed in both groups, but differences were not significant between the experimental groups. In the lathed titanium rods group and the shorter interval group, inflammatory cell infiltration was significantly higher. Finished titanium rods and longer interval groups had markedly decreased tendences in histologic reaction ratings. As a conclusion, although certificated titanium might be safe to use, difference of biocompatibility were observed depending on the method of surface finish. By identifying biocompatibility as a long-term standardized animal study, we can develop progressed internal fixation device that is safe for human beings.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.35 no.4
• /
• pp.147-155
• /
• 2019

In this study, flexural tests of granite reinforced with titanium metal rods were carried out to repair and restore the damaged stone-made cultural heritage, the Stone Pagoda of the Mireuksa Temple Site. A total of twelve specimens were tested. The primary test parameters are the reinforcement ratio and the location of the reinforcement. For restoration, epoxy resin was used for joining the separated stones, and titanium metal rods were used for structural reinforcement. Test results showed that the flexural failure took place in specimens with a reinforcement ratio of 0.8% or less, and shear failure occurred when the reinforcement ratio was 1.68% or more. The peak load of the reinforced stone was found to be highly related to the reinforcement ratio. The peak load increased with increasing the reinforcement ratio. Also, the flexural behaviors of the reinforced stones were affected by the location of the reinforcement. Based on the test results, this study recommends the reinforcement ratio of the reinforced granite to induce ductile behavior.

• Composites Research
• /
• v.34 no.3
• /
• pp.186-191
• /
• 2021

The lumbar spinal fusion is a treatment performed to restore the stability of the degenerated lumbar. In this study, the intervertebral discs between two or more segments are removed and a bone graft is inserted to harden the segments. The pedicle screw system is inserted to vertebral bodies to fix two or more segments so that they can be firmly fused. In this study, a total of 7 patient-specific lumbar finite element models were created and pedicle screw systems were installed. The connecting rods made of titanium and CFR-PEEK was inserted to the generated models. Finite element analysis was conducted for four representative spine behaviors and statistical analysis was performed to investigate the biomechanical effects by the material properties of connecting rods. The intradiscal pressure of adjacent segments and the range of motion of the joints of each segment were investigated. In the subjects who used CFR-PEEK instead of Ti for connecting rods, the intradiscal pressure of adjacent segments tend to decrease and the range of motion of each segment tend to increase. However, no statistically significant difference in tendency was observed under all loading conditions.

• The Journal of Korean Academy of Prosthodontics
• /
• v.44 no.5
• /
• pp.642-653
• /
• 2006

Purpose : The purpose of this study was to investigate the effect of the output energy(voltage) of laser welding on the strength and properties of joint of cast titanium(CP Gr II) and titanium alloy(Ti-6Al-4V). Material and method : Cast titanium and its alloy rods(ISO6871) were prepared and perpendicularly cut at the center of the rod. After the cut halves were fixed in a jig, and the joints welded with a laser-welding machine at several levels of output voltage of $200V{\sim}280V$. Uncut specimens served as the non-welded control specimens The pulse duration and pulse spot size employed in this study were 10ms and 1.0mm respectively. Tensile testing was conducted at a crosshead speed of 0.5mm/min. The ultimate tensile strength(MPa) was recorded, and the data (n=6) were statistically analyzed by one-way analysis of variance(ANOVA) and Scheffe's test at ${\alpha}$=0.05. The fracture surface of specimens investigated by scanning electron microscope (SEM). Vickers microhardness was measured under 500g load of 15seconds with the optimal condition of output voltage 280V. Results : The results of this study were obtained as follows, 1. When the pulse duration and spot size were fixed at 10ms and 1.0mm respectively, increasing the output energy(voltage) increased UTS values and penetration depth of laser welded to titanium and titanium alloy. 2. For the commercial titanium grade II, ultimate tensile strength(665.3MPa) of the specimens laser-welded at voltage of 280V were not statistically(p>0.05) different from the non-welded control specimens (680.2MPa). 3. For the titanium alloy(Ti-6Al-4V), ultimate tensile strength(988.3MPa) of the specimens laser-welded at voltage of 280V were statistically(p<0.05) different from the non-welded control specimens (665.0MPa). 4. The commercial titanium grade II and titanium alloy(Ti-6Al-4V) were Vickers microhardness values were increased in the fusion zone and there were no significant differences in base metal, heat-affected zone.

• Journal of Hydrogen and New Energy
• /
• v.2 no.1
• /
• pp.47-56
• /
• 1990

Pure titanium rods were oxidized by anodic oxidation, furnace oxidation and flame oxidation and used as a electrode in the photodecomposition of water. The maximum photoelectrochemical conversion efficiency(${\eta}$) was found for flame oxidized electrode ($1200^{\circ}C$ for 2 min in air), 0.8 %. Anodically oxidized electrodes have minimum photoelectrochemical conversion efficiencies, 0.3 %. Furnace oxidized electrode ($800^{\circ}C$ for 10min in air) has 0.5% phtoelectrochemical efficiency and shows a band-gap energy of about 2.9eV. The efficiency shows a parallelism with the presence of the metallic interstitial compound $TiO_{O+X}$(X < 0.33) at the metal-semiconductor interface, the thickness of the sub oxide layer and that of the external rutile scale.

• Conservation Science in Museum
• /
• v.31
• /
• pp.71-103
• /
• 2024

The National Museum of Korea Conservation science division conducted a precise diagnosis and a non-destructive investigation to comprehensively assess the overall damage of the Twin-lion stone lantern from the Godalsa Temple site, Yeoju to be placed on display in the museum's outdoor stone garden, then reviewed the relevant conservation and management plan and applied conservation treatment to the artifact. The museum carried out the treatment in the following order: precise diagnosis; dismantling of the previously-restored part of the roof stone; reinforcement and restoration of the roof structure with new stone; restoration of the previously-restored part of the lantern's support stone (jungseok); surface texture treatment to the restored area; cleaning (basic, laser); and color matching. The previously-restored part of the roof stone was removed and restored with new stone material, based on the results of a safety diagnosis regarding the separation at the said part. Granite from the Sangju area was selected as the material for the restoration in consideration of the results of mineral analysis as well as the surface color and particle size. The new stone was divided into three pieces based on the descending edges of the octagonal roof structure and joined together using epoxy resin. The structure was further strengthened by inserting titanium rods. It is expected that the status diagnosis and conservation treatment of the twin-lion stone lantern from the Godalsa Temple site in Yeoju will be used as a reference for the future conservation and management of outdoor displays of stone cultural heritage.

• Journal of Korean Neurosurgical Society
• /
• v.58 no.5
• /
• pp.412-418
• /
• 2015

Objective : To investigate the effects of posterior implant rigidity on spinal kinematics at adjacent levels by utilizing a cadaveric spine model with simulated physiological loading. Methods : Five human lumbar spinal specimens (L3 to S1) were obtained and checked for abnormalities. The fresh specimens were stripped of muscle tissue, with care taken to preserve the spinal ligaments and facet joints. Pedicle screws were implanted in the L4 and L5 vertebrae of each specimen. Specimens were tested under 0 N and 400 N axial loading. Five different posterior rods of various elastic moduli (intact, rubber, low-density polyethylene, aluminum, and titanium) were tested. Segmental range of motion (ROM), center of rotation (COR) and intervertebral disc pressure were investigated. Results : As the rigidity of the posterior rods increased, both the segmental ROM and disc pressure at L4-5 decreased, while those values increased at adjacent levels. Implant stiffness saturation was evident, as the ROM and disc pressure were only marginally increased beyond an implant stiffness of aluminum. Since the disc pressures of adjacent levels were increased by the axial loading, it was shown that the rigidity of the implants influenced the load sharing between the implant and the spinal column. The segmental CORs at the adjacent disc levels translated anteriorly and inferiorly as rigidity of the device increased. Conclusion : These biomechanical findings indicate that the rigidity of the dynamic stabilization implant and physiological loading play significant roles on spinal kinematics at adjacent disc levels, and will aid in further device development.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.1
• /
• pp.39-46
• /
• 2008

The end plates of fuel cell assemblies are used to fasten the inner stacks, reduce the contact pressure, and provide a seal between Membrane-Electrode Assemblies (MEAs). They therefore require sufficient mechanical strength to withstand the tightening pressure, light weight to obtain high energy densities, and stable chemical/electrochemical properties, as well as provide electrical insulation. The design criteria for end plates can be divided into three parts: the material, connecting method, and shape. In the past, end plates were made from metals such as aluminum, titanium, and stainless steel alloys, but due to corrosion problems, thermal losses, and their excessive weight, alternative materials such as plastics have been considered. Composite materials consisting of combinations of two or more materials have also been proposed for end plates to enhance their mechanical strength. Tie-rods have been traditionally used to connect end plates, but since the number of connecting parts has increased, resulting in assembly difficulties, new types of connectors have been contemplated. Ideas such as adding reinforcement or flat plates, or using bands or boxes to replace tie-rods have been proposed. Typical end plates are rectangular or cylindrical solid plates. To minimize the weight and provide a uniform pressure distribution, new concepts such as ribbed-, bomb-, or bow-shaped plates have been considered. Even though end plates were not an issue in fuel cell system designs in the past, they now provide a great challenge for designers. Changes in the materials, connecting methods, and shapes of an end plate allow us to achieve lighter, stronger end plates, resulting in more efficient fuel cell systems.

• Applied Chemistry for Engineering
• /
• v.3 no.1
• /
• pp.88-99
• /
• 1992

For the development of semiconducting photoelectrode to be more stable and efficient in the process of photoelectrolysis of the water, pure titanium rods were oxidized by anodic oxidation, furance oxidation and flame oxidation and used as electrodes. The Indium islands were formed by electrodeposition of "In" thin film on $TiO_2$ and Ti by electrodeposition. Also $A1_2O_3$ and NiO islands were coated on Ti by the electron-beam evaporation technique. The maximum photoelectrochemical conversion efficiency(${\eta}$) was 0.98% for flame oxidized electrode($1200^{\circ}C$ for 2min in air). Anodically oxidized electrodes have photoelectrochemical conversion efficiency of 0.14%. Furnace oxidized electrode($800^{\circ}C$ for 10min in air) has 0.57% of photoelectrochemical efficiency and shows a band-gap energy of about 2.9eV. The $In_2O_3$ coated $TiO_2$ exhibits 0.8% of photoelectrochemical efficiency but much higher value of ${\eta}$ was obtained with the Increase of applied blas voltage. However, $Al_2O_3$ or NiO coated $TiO_2$ shows much low value of ${\eta}$. The efficiency was dependent on the presence of the metallic interstitial compound $TiO_{0+x}$(x<0.33) at the metal-semiconductor interface and the thickness of the suboxide layer and the external rutile scale.

• The Journal of Korean Academy of Prosthodontics
• /
• v.43 no.6
• /
• pp.745-750
• /
• 2005

Statement of problem. Resonance frequency analysis has been increasingly served as a non-invasive and objective method for clinical monitoring of implant stability. Many clinical studies must be required for standardized data using RFA. Purpose. This study was performed to evaluate RFA value changes in two anodized implant groups. Material and method. Among a total of 24 implants, twelve screw shaped implants as a test group (H2-R8.5) were manufactured, which had a pitch-height of 0.4 mm, an outer diameter of 4.3 mm, a length of 8.5 mm, and external hexa-headed, were turned from 5 mm rods of commercially pure titanium (ASTM Grade IV, Warantec Co., Seoul, Korea), and another twelve implants as a control group were $Br{\aa}nemark$ Ti-Unite MK4 (diameter 4.0 mm, length 8.5 mm). Each group was installed in tibia of rabbit. Two implants were placed in each tibia (four implants per rabbit). Test two implants were inserted in right side and control two in left side. ISQ values were measured using $Osstell^{TM}$ (Integration Diagnostics Ltd. Sweden) during fixture installation, and 12 weeks later and evaluated the RFA changes. Results. Mean and SD of baseline ISQ values of test group were $75.0{\pm}3.4$ and $68.7{\pm}8.1$ for control group. Mean and SO of ISQ values 12 weeks after implant insertion were $73.2{\pm}4.7$ for test group and $72.6{\pm}3.9$ for control group. There were no statistically significant differences between groups in ISQ values after 3 months (P>0.05). From the data, RFA gains after 3 months were calculated, and there was statistically significant difference between groups (P<0.05). Conclusion. Although there were RFA changes between groups, implant stability after experimental period shows alike tendency and good bone responses.