• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
• /
• pp.131-131
• /
• 2003

The advent of photonic technologies in the field of communications and data transmission has been heavily increasing the demand in integrated optical (IO) circuits capable of accomplishing not only simple tasks like signal, but also more sophisticated functions like all-optical signal routing or active multiplexing/demultiplexing. In the last decade, sol-gel technology has been widely used to prepare optical materials. Sol-gel processes show many promises for the development of low-loss, high-performance glass integrated optical circuits. However, crack formation is likely to occur during heat treatment in thick gel films. In order to overcome the critical thickness limitation, the organic-modified silicate has been widely used. In this case coating matrices have been prepared from the organo-silanes of T structures, acidic catalyst and the as-prepared gel films have been heat-treated below 200$^{\circ}C$ to avoid the crack formation and the degradation of organic components. However, the films prepared in the acidic condition and the low heat temperature make the films contain high OH groups which is the major optical loss function. In this work, C$\sub$6/H$\sub$5/SiO$\sub$1.5/ films were prepared on silicon substrate by sol-gel method using base catalyst in a PTMS/NH$_4$OH/H$_2$O/C$_2$H$\sub$5/OH system. The sol showed spinable viscosity at 50 wt% of solid content, and neglectable viscosity change with time. The films were crack-free and transparent after curing at 450 $^{\circ}C$, and highly condensed to minimize OH content in C$\sub$6/H$\sub$5/SiO$\sub$1.5/ networks. The effects of heat treatment of the films are characterized on the critical thickness, the chemical composition and the refractive indices by means of SEM, FT-IR, TGA, prism coupler, respectively.

• 대한치과보철학회지
• /
• 제42권4호
• /
• pp.333-343
• /
• 2004

Statement of problem: In its preceding work, change in surface characteristics were investigated in consideration that both microtopograpy and macroscopic configuration of implants surface are two of the most important factors, in that they can construct agreeable environment by raising surface energy, to affect osseointegration and biocompatibility explained by cell proliferation. Purpose: This study focused on examining cytocompatibility of dental implants materials Ti-Ag alloys, of which mechanical and electrochemical superiority to cp-Ti or Ti6Al4V were verified, in comparison with that of cp-Ti, and Ti6Al4V. Materials and methods: In this regard, MTT tests for L-929, the fibroblast connective tissues and cell proliferation tests for osteoprogenitor cells, MC3T3-E1 were performed on cp-Ti, Ti6Al4V, and Ti-Ag alloys following thermal oxidation according to appropriate heat treatment temperature(untreated, 400, 600, $800^{\circ}C$) and heat treatment duration(untreated, 0.5, 1, 4 hr). Results: The MTT tests on fibroblasts L-929 resulted in cell viability of over 90% in all experimental group entities, where, especially, the 100% of the viability for Ti-Ag alloys specimens accounted for the slightest adverse effect of ions release from those alloys on the cell. In MC3T3-E1 proliferation tests, the population of cells in the experimental group was roughly increased as experimentation proceeded, after two to four days. Proliferation showed highest viability for most of specimens, including Ti2.0Ag, treated at $600^{\circ}C$. Conclusion: In conclusion, it is the heat treatment temperature, not the duration that has considerable effects on thermal oxidation of specimens. Ti-Ag alloys treated at $600^{\circ}C$ proved to have the best surface morphology as well as cytocompatibility when compared with Ti or Ti6Al4V for short-term biocompatibility tests.

• 소성∙가공
• /
• 제16권6호
• /
• pp.463-466
• /
• 2007

Micro-wire made from straightening process invents high added value and it has been adopted many industrial fields. Therefore, many research activities about straightening process are advanced actively. It is known that fine straightness of micro-wire can be obtained by removing residual stress induced during the manufacturing processes. Generally, residual stress is removed or minimized through several drawing processes with heat treatment. In this study, the residual stress at each straightening process is calculated and monitored by finite element analyses and the main reason of stress change is investigated.

• 한국산학기술학회논문지
• /
• 제13권6호
• /
• pp.2648-2654
• /
• 2012

본 연구는 피부미용실에서 많이 적용하고 있는 다양한 도구를 이용한 등마사지의 효과를 알아보고자 하였으며 마사지 전후의 체열변화를 비교분석함으로 가장 효과적인 방법을 제시하여 등관리 프로그램을 개발하는 기초자료를 제공하고자 하였다. 수기와 초음파기, 석션기를 이용하여 각각의 도구에 5명씩의 35세에서 45세 사이의 전남 광주시에 거주하는 여성들에게 2011년 7월 3일부터 7월 10일까지 시행하였다. 마사지전과 20분간의 마사지 시행후 각각 체열변화를 체열진단기 DITI IRIS-XP로 측정하였다. 수집된 자료는 SPSS 18.0 program을 이용하여 t-test를 실시하였다. 그 결과는 수기마사지전 $30.82{\pm}0.52$에서 수기마사지후 $35.06{\pm}0.36$로 체온상승이 유의하게 나타났고(p<.001), 초음파 마사지전 $30.66{\pm}0.53$에서 초음파 마사지후 $35.14{\pm}0.39$로 체온상승이 유의하게 나타났으며(p<.001),석션마사지전 $30.93{\pm}0.47$에서 석션마사지후 $39.25{\pm}0.19$로 체온상승이 유의하게 나타났다(p<.001). 수기와 초음파기, 석션기는 마사지도구로서 체온상승에 모두 효과적이며 특히 석션기를 이용한 마사지가 체온상승에 가장 효과가 높은 것으로 나타났다. 따라서 석션기는 등관리 프로그램을 개발하여 활용하는 가장 효과적인 도구인 것으로 분석되었다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.1601-1606
• /
• 2007

In order for high strength aluminum alloys to be used in transportation systems and the aerospace industry, excellent mechanical and physical properties are required. In particular, excellent anti-abrasion property is indispensable for parts that require driving force. In general, surface treatment technologies such as high frequency heat treatment, gas solid carburizing, surface rolling, shot peening are used as ways of improving anti-abrasion property. Among various surface treatment technologies, this research chose shot peening processing for Al7075-T6, which is well known as representative high-strength alloy steel. Wear characteristics were compared and analyzed after shot peening processing with shot ball velocities of 40m/s and 70m/s in order to investigate the effects of shot peening processing on wear characteristics.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2006년도 춘계학술대회 논문집
• /
• pp.318-321
• /
• 2006

In this strudy, the free-bulge test and FE analysis have been used to define the fracture criteria based on the cockroft and Latham's criterion in warm hydroforming of Al 6061 tube. Full annealing and T6 treatment for heat treatment of Al 6061 tube ware used in this study. As-extruded, full annealed and T6-treated Al 6061 seamless tubes were prepared. To evaluate the hydroformability, uni-axial tensile test and bulge test were performed between room temperature and $200^{\circ}C$. And measured flow stress was used to simulate the warm hydroforming. A commercial FEM code, DEFORM-$2D^{TM}$, was used to calculate the damage value. A forming limit based ductile fracture criteria has been proposed by the results of experimental and FE analysis. The calculated values for fracture criteria will be efficient to predict the forming limit in hydroforming for real complex shaped part.

• 한국연초학회지
• /
• 제13권1호
• /
• pp.5-12
• /
• 1991

(A series of cigarettes made from) RTL containing different leveles of added sugars (2.0. 5.0 and 8.0%) and acids(0.4, 0.8 and 1.2%) have been examined. Compared to the control cigarette there was reduced in the delivery of tar and nicotine in smoke on 5.0% addition of glucose there was a signification reduced the delivery of nicotine the addition of glucose or fructose decreased the delivery of nicotine tar and co. However, tar in smoke was an increased in the delivery of tar and nicotine was observed, when sucrose and lactose were the added sugars. The smoking taste by the addition of glucose and fructose on R.T.L. was found to be milder than by the others sugars. Tar and nicotine deliveries showed a decreasing trend with the addition of organic acid and tartaric acid among the organic acid described above had greater effect than the others acids 1.2% addition of tartaric acid gave some 11-31% reduction in tar and nicotine delivery and a fall of smoke pH from 4.49 was found. Smoking taste by the addition of lactic acid and tartaric acid had milder than the others and heat treatment for 10 minutes at 13$0^{\circ}C$ gave also better on smoking: taste. The addition of mixture of sugars and organic acid (glucose 5% + lactic acid 0.6% + tartaric acid 0.6%) and then the successive heat treatment for 10 minutes at 13$0^{\circ}C$ improved greatly the Quality of R.T.L. and nicotine were reduced to 11-28% and pH was changed from 5.40 to 3.89.

• 열처리공학회지
• /
• 제6권1호
• /
• pp.17-25
• /
• 1993

The Cu - $Nb_3Sn$ composites wire as a superconducting material was prepared by in situ method as follow: Cu - 15wt.% Nb alloys which were melted in a high -frequency induction furnace and casted in bar were cold-worked up to the final diameter of 0.24 mm, electroplated with Sn, pre-treated in two steps and then diffused at $550{\sim}650^{\circ}C$ for 24 ~ 96 hrs. The overall $J_c$ and $T_c$ of the specimens were measured by the four point-probe method at 10 K in the magnetic field of 0 Tesla. The overall $J_c$ of the composites wire which diffused at $550^{\circ}C$ after pre-treating in two steps were generally higher than those of the wire at either $600^{\circ}C$ or $650^{\circ}C$. For the specimens diffused at $550^{\circ}C$, the overall $J_c$ were increased until 72 hrs. of diffusion time and then decreased. However, in case of diffusion at $600^{\circ}C$ and $650^{\circ}C$, the overall $J_c$ were gradually decreased from the beginning. The maximum overall $J_c$ obtained in this experiment was $1.3{\times}10^4\;A/cm^2$, which was measured for the specimen diffused at $550^{\circ}C$ for 72 hrs. When the specimens were diffused at $550^{\circ}C$ for 72 hrs, after pre-treating, the measured critical temperature, $T_c$ was 16.19 K. Similar $T_c$ value were obtained in other specimens regardless of diffusion time and temperature.

• 열처리공학회지
• /
• 제6권1호
• /
• pp.1-8
• /
• 1993

In this paper, the surface roughness influenced by Sm45C hardness in high frequency induction hardening and mechanical characteristics for the changed Hv 598 part and the unchanged hardness Hv 223 part by use of cermet and ceramic cutting tools was experimentally examined. Finally, we could be had some important results by processing surface roughness on cutting conditions such as cutting speed, feed rate, depth of cut and changes of tool nose radius. The results are summarized as follows. 1. In case of the same cutting condition, the hardness of workpiece was high and acquired the best processing surface roughness when the radius of the tool nose had 0.8 mm and feed rate was 0.04 mm/rev. 2. In case of the hardness of workpiece, though the cutting speed didn't have an effect on processing surface roughness, the less feed rate and the more processing surface roughness improved. On the other hand, the low inside the hardness of workpiece, the more cutting speed and the more feed rate increase, the processing surface of roughness improved. 3. Regardless of the hardness of workpiece, the change of the cutting depth didn't have great effect on the surface roughness. 4. On cutting the high surface hardness part with cutting tools of cermet and ceramic, it can be acquired the higher processing surface roughness because it hadn't been taken effect on cutting speed, In case of the cutting process of the low inside hardness part the two cutting tools have acquired the similar processing surface roughness.

• 소성∙가공
• /
• 제28권1호
• /
• pp.5-14
• /
• 2019

In order to reduce the weight of automobile parts, automobile parts using aluminum alloy are being developed. Aluminum alloy for automobile parts is mainly made of Al6xxx (Al-Mg-Si) type alloy, which is excellent in hot forming property, and it can increase mechanical properties by the use of heat treatment. In this study, hot forming was performed using Al6082. Before the hot forming, the forming analysis was performed using the DEFORM-3D finite element analysis program in this case. For the forming analysis, the heat transfer coefficient was derived from the experiment, and the forming analysis was performed by applying it. At the forging analysis, the temperature of Al6082 material was set to 813K and that of the mold was set to room temperature. After the forging analysis, the experiment was performed, and the forging analysis and the experimental results were compared.