• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.104.2-104.2
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• 2012

이종 재료의 접합에 대한 연구는 단일 재료에서 얻을 수 없는 물리적/기계적 특성과 이종 재료의 우수한 특성을 얻을 수 있다는 장점이 있어 국내외 적으로 연구가 활발히 진행되고 있다. 이러한 이종 접합 기술은 구조재료와 에너지 변환분야에 가장 많이 사용되고 있으며, 그 외 광촉매와 Thin film, 경량구조재료 등에도 사용되고 있다. 그 중 FGM(Functional Graded Materials)는 조성의 점진적인 변화를 통하여 접합하는 방법으로 이종 재료 접합 시 발생하는 내부 응력을 해소해줌으로써 적합한 방법이라고 할 수 있다. FGM 제작에 사용되는 방법으로 널리 알려진 것들로는 plasma spraying, 원심주조, 분말 야금법, PVD, CVD 그리고 EPD(electrophoretic deposition) 등이 있다. 이중에서 EPD는 수용액이나 유기용매와 같은 분산매체 중에 콜로이드 입자의 표면에 대전되는 전하를 이용하여, 외부에서 전장을 걸어서 입자의 움직임을 제어하는 기술이다 EPD는 코팅 속도가 상대적으로 빠르고 두꺼운 코팅 층 제작이 가능하다. 또한 바인더, 윤활제 또는 가소제를 사용하지 않고 다양한 종류와 모양의 기판 위에 균일한 코팅이 가능하다는 장점이 있다. 본 연구에서는 Ni substrate를 이용하여 그 위에 Ni과 $Al_2O_3$의 조성을 점진적으로 변화시켜 FGM을 EPD 방법으로 코팅하였다. 여기서 사용된 Ni은 높은 녹는점과 좋은 연성으로 인해 성형이 용이하여 구조재료로 적합하며, $Al_2O_3$는 고내열성과 내부식성을 가지며 경도가 높다는 장점이 있다. 본 연구에서는 EPD 방식을 이용하여 Ni/$Al_2O_3$ FGM을 코팅하였으며, 코팅 후 발생하는 substrate와의 접착력 문제를 해결하기 위해서 건조 방식과 substrate의 표면 상태를 최적화하여 다층의 Ni/$Al_2O_3$ FGM을 코팅 및 소결하였다. Zeta-potential 측정을 통해 electrophoretic mobility와 suspension의 분산 안정도를 평가 할 수 있었으며, X-ray 회절 분석(XRD)을 통하여 Ni 의 환원 여부를 확인하였다. 또한 Scanning electron microscopy(SEM) 분석을 통하여 미세구조 분석을 하였고, 최종적으로 Electron Probe Micro Analyzer (EPMA) 를 이용하여 다층 구조의 조성변화를 확인함으로 Ni/$Al_2O_3$의 FGM 코팅이 이루어졌음을 확인하였다.

• Advances in Computational Design
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• v.5 no.4
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• pp.363-380
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• 2020

In this paper, a cylindrical shell is immersed in a non-viscous fluid using first order shell theory of Sander. These equations are partial differential equations which are solved by approximate technique. Robust and efficient techniques are favored to get precise results. Employment of the Rayleigh-Ritz procedure gives birth to the shell frequency equation. Use of acoustic wave equation is done to incorporate the sound pressure produced in a fluid. Hankel's functions of second kind designate the fluid influence. Mathematically the integral form of the Lagrange energy functional is converted into a set of three partial differential equations. Throughout the computation, simply supported edge condition is used. Expressions for modal displacement functions, the three unknown functions are supposed in such way that the axial, circumferential and time variables are separated by the product method. Comparison is made for empty and fluid-filled cylindrical shell with circumferential wave number, length- and height-radius ratios, it is found that the fluid-filled frequencies are lower than that of without fluid. To generate the fundamental natural frequencies and for better accuracy and effectiveness, the computer software MATLAB is used.

• Journal of Korean Foot and Ankle Society
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• v.6 no.2
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• pp.201-207
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• 2002

Purpose: To present the clinical analysis of the results obtained in 38 cases of displaced intraarticular calcaneal fractures undergone combined percutaneous axial pin fixation of calcaneal body and minimal internal fixation using extensile lateral approach. Materials and Methods: From March 2000 to February 2002, thirty-eight displaced intraarticular fractures of the calcaneus in 35 patients were fixed with 3.5mm cannulated screws and percutaneous 2.5mm K-wires. The extensile lateral approach was used in all cases. The average follow-up period was 16 months. Clinical evaluation was assessed according to the Ankle-Hind Foot Scale of American Orthopedic Foot and Ankle Society. Results: The clinical results were graded as excellent in 8 cases(21%), good in 22 cases(58%), fair in 6 cases(16%), and poor in 2 cases(5%). Two cases of poor result were type IV of Sanders classification. The postoperative reduction status of the articular surface was analyzed by computed tomography in all cases and was found to be less 2mm of step off in 30 cases and between 2 and 4mm in 8 cases. Unsatisfactory results were correlated with severity of articular comminution and failure to obtain accurate reduction of the articular surface. Using early functional postoperative care, all fractures healed without secondary displacement except 1 case on an average of ten weeks. Two cases had superficial necrosis of the wound margins, however, secondary wound healing was uneventful and skin grafting was not needed. Conclusion: Combined minimal internal fixation and percutaneous pin fixation using extensile lateral approach is useful operative method of intraarticular calcaneal fractures because providing enough stability to permit functional aftercare and allowing excellent anatomical reduction. In addition, this method diminishes the risk of lateral soft tissue problems.

• Journal of the Korean Society of Costume
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• v.22
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• pp.263-276
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• 1994

The achievement of notable social reoforms attained during the period of 19th and 20th centuries needlessly speaking remodelded the social environmental into several different patterns such as :1) high industrialization 2) propensity to consume 3) up graded overall social stands. Accordingly the industrial world of the but-tons too established the mess production syhstem by breaking from convention of hand-craft work of 17th century. The raw materials used in the production line on buttons during the 20th century are almost all-kind of materials one can possibly named including cheap plastic which enabled production lines to produce cheaper but higher productivities of the buttons being produced, The design (incused design) used in the 19-20h centuries are : men landscape, sports features, birds, livestocks, bugs, or geomatric features, tec, 1, The classification o f the buttons by materials Techniques shapes colors marking (Incused design) used in the productionof buttons in the England United States of America Laska Italy france Denmark Japan and India are categolizzed as : natural raw materials and syntetical resines. 1) Of the natural raw materials used are : Matal Enamel Iodine Agate, Coral, Green jade(Jasper) Granite, Wood, Ivory, Horn and bone etc. 2) The sythetical resin used in the button in-dustries are : Artificial jewell glass Acrylic material Styroform Celluloid and Nylon etc. 2. The thecnique quoted in producing buttons are hand craft work inlay work precision casting press mosic dye etching, processing, engraving and embossed carving etc. 3. The major designs used in the buttons in -dustries are : Round shape however elliptical column angular and edge shape often used. 4. The colors used are : The multi-colors were highly used than mono-colored materials such as : Adjoining Color and Contrast Color. The highest consideration to be considered in choosing the colors for the buttons are harmonization and matching factor with the garment or dresses to be wore. 5. The major design(incused design) on the buttons are embodiment and the design were also used in order of abstractive-combination abstractive with has offers much surprising. The button industries during the 19th and 20th centuries were not only the determination factors those can judge the value of self-pride of Nation and which were far beyond the in-dustrial arts in those days but also highly refelected and influenced by cultural sense ideology and self-pride of the Nation of those period. The followings are details of the role of the buttons categolized in the order of functional ornamental and symbolical aspects : 1. The functional role : The functional role of the buttons were simply designed for dress how-ever the buttons beyond from this role of function now a days. 2. The ornamental role : The ornamental role of he button beyond from this role of the button were effectuated by : 1) shape materials colors 2) technique locations size and design (incused design) 3) The ramaterials used for buttons shall not be over looked because it is highly depends on the taste sense and combination of harmony with the garment to be wore. 4) The color of the buttons are made well contrasted with the color of garments just as in the case of other artistical area such as matchs with the color of garment of contrast with brigtness of colors contrasted as complementary color and so and so. 5) The technique being adoped are: precision casting press handcraft inlay work etching mosic etc,. Since the buttons are no longer a simple catching devise used to fasten together the different part of the dress but now it has formed own and occupied the independent role in the garment or dresses location can be de-termined and varying depending on the ideas of designers. The size of the buttons has no specific limits, However the variation has widely dependined on the entire circumperence rhythm contrast harmonization of the garments. 3. The symbolical role : Since the button is no longer a just a simple devise for catching and fastening device used fastening together the different part of the garments but now were built a independent area as major part of the Garment and well reflected all kinds of occupations political background cultural as-pect etc. on the buttons. The design of buttons in the western circles are more simplified but they are polished looks and their techniques of manufacturing are comination of both machanis and handcraft. The colors used in the buttons are pretty well harmonized with garment(dress). Almost all kind of materials can be used in the but-tons however materials used in the buttons are : Bone of livestocks ivory, turtle shell are no longer used because the prevention of cruely of animal. On the contraly the level of buttons indus-try of Korea is far to reach and catch up with the level of western circles. It is highly suggested therefore the but-tons industrial field of Republic of Korea shall place and encouragement in producing beter industrial environment of the buttons based on the traditional and cultural aspect of republic of Korea to produce both manufacturing of qulified and best designed and colored buttons.

• Journal of Korean Foot and Ankle Society
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• v.5 no.2
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• pp.142-148
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• 2001

Purpose: To investigate the short term result of the first metatarsophalangeal arthrodesis for treating the hallux valgus deformity of rheumatoid arthritis, using a lag screw and dorsal mini-plate. Materials and Methods: From December 1999 to September 2001, The first metatarsophalangeal arthrodesis of 14 cases (9 patients) was underwent, using a lag screw and dorsal mini-plate. The follow-up period was averaged in 14.6 months. The subjective findings with respect to pain, functional aspect of ability to stand and walk, and to shoe-wearing were evaluated. The objective findings, such as the gross alignment and the radiological measurements for the hallux valgus angle, 1,2 intermetatarsal angle, and dorsiflexion angle were also studied. Results: After the arthrodesis of the first metatarsophalangeal joint, the subjective improvement in pain, function and alignment was graded as excellent in seven (50%) feet, good in seven (50%) feet, and fair or poor in none. The hallux valgus angle and 1,2 intermetatarsal angle were reduced from $44.1{\pm}7.1$ and $15.5{\pm}6.2$ degrees to $13.6{\pm}2.6$ and $10.2{\pm}2.2$ degrees respectively. The dorsiflexion angle was measured in $20.3{\pm}3.7$ degrees after the fusion. The radiological fusion was observed at average 8 weeks after the operation in all cases. The overall complication of the procedure was few, except the delayed wound healing in one. Conclusion: The arthrodesis of the first metatarsophalangeal joint using a lag screw and dorsal mini-plate was regarded as an excellent method of various operative modalities to correct the rheumatoid hallux valgus deformity.

• Applied Microscopy
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• v.3 no.1
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• pp.29-38
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• 1973

Introduction. The human cutaneous scars manifest themselves many ways in different types according to the factors such as the age, sex, race of the patient as well as the location,. kind and heal ing process of the wound. Among the scars it is quiet difficult to verify the clinical course of the hypertrophic or keloidal scars from the true keloids. However, clinical observations indicate that stress, either mechanical or in the forms of chronic infections, can induce a functional change in the fibroblasts causing an excessive production of collagenous matrix. In this study, we preliminary attempt to justify any difference of the cellular structure between keloids and hypertrophic scars by using electron microscope. Material and Methods. A total of 23 cases: 2 scars, 2 hypertrophic scars and 19 keloids are examined. Immediately, the biopsy tissue was fixed in 10% neutral formalin and 4% glutaraldehyde solution in phosphate buffer for 4 hours, post fixed in 1 % osmium tetraoxide for two hours, dehydrated with graded alcohol, and embedded in Epon 812. Thick sections were stained with hematoxylin eosin, periodic acid-Schiff(PAS) and Van Gieson stain. Thin sections were cut and uranyle acetate, lead citratestain and examined with the electron microscope. Result. The morphologic features of keloid showed thick, homogenously eosinophilic bands of collagen and numberous large active fibroblasts. The hypertrophic scar and soft scar are more cellular than keloid and composed thinner collagenous fiber. For this paper in the etiology of keloids can not as be defined, but and interesting keloidal tissue fibroblast showed irregular nucleus with irregular shape dense bodies and fibril materials contained in to the cytoplasm.

• Journal of the Korean institute of surface engineering
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• v.32 no.2
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• pp.144-156
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• 1999

Thermal Barrier Coating with Functional Gradient Materials (FGM-TBC) can play an important role to protect the parts from harmful environments in high temperatures such as oxidation, corrosion, and wear and to improve the efficiency of aircraft engine by lowering the surface temperature on turbine blade. FGM-TBC can increase the life spans of product and improve the operating properties. Therfore, in this study the evaluations of mechanical and thermal properties of FGM-TBC such as fatigue, oxidation and wear-resistance at high temperatures have been conducted. The samples of both the TBC with 2, 3, 5 layers (YSZ/NiCrAlY) to be produced by Air Plasma Spray method (APS) and the bulk TBC with 6 layers to be produced by Plasma Assisted Sintering method (PAS) were used. Furthermore, residual stress, bond strength, and thermal conductivity were evaluated. The average thickness of the APS was 500$\mu\textrm{m}$ to 600$\mu\textrm{m}$ and the average thickness of the PAS was 3mm. The hardness number of the top layer of APS was 750 Hv to 810Hv and that of PAS was 950 Hv to 1440Hv. The $ZrO_2$ coating layer of APS was composed of tetragonal structure after spraying as the result of XRD analysis. As shown in the results of the high temperature wear test, the 3 layer coating of APS had the best wear resistance at $800^{\circ}C$ and the 5 layer coating of APS had the best wear resistance at $600^{\circ}C$. But, these coatings had the tendency of the low-temperature softening at $300^{\circ}C$. The main mechanism of wear was the adhesive wear and the friction coefficient of coatings was increased as increasing the test temperatures. A s results of thermal conductivity test, the ${\Delta}T$ of the APS coating was increased as number of layer and the range of thermal conductivity of the PAS was $800^{\circ}C$ to $1000^{\circ}C$.

• Journal of the Korean Arthroscopy Society
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• v.9 no.2
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• pp.167-173
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• 2005

Purpose: The purpose of this study is to evaluate the clinical results of posterior cruciate ligament (PCL) and posterolateral structure (PLS) reconstruction using bilateral hamstring tendon autografts. Materials and Methods: From October 2002 to March 2004, ten patients were received PCL and PLS reconstruction simultaneously using bilateral hamstring autografts. PCL was reconstructed using ipsilateral hamstring tendon and fixed with cross pins and Intrafix (Mitek, Norwood, MA). PLS was reconstructed using contralateral hamstring tendon. The mean follow up was 17 months. Clinical assessments consisted of Lysholm knee scores, International Knee Documentation Committee (IKDC) evaluation form and posterior stress radiographs. External rotation of tibia was evaluated at $30^{\circ}\;and\;90^{\circ}$ knee flexion using Noyes and Barber-Westin's classification. Contralateral harvest site morbity was evaluated using IKDC evaluation form and flexion power of the knee. Results: Mean posterior displacement of tibia using stress radiographs was improved from 13.3 mm to 3.7 mm. In tibial external rotation evaluation, 7 patients were functional, 2 patients were partially functional and one failure. The average Lysholm knee score improved from 54 preoperatively to 86 postoperatively. At the final IKDC evaluation, 8 patients were graded as nearly normal, 2 were graded as abnormal. In contralateral harvest site morbidity evaluation, 2 patients complained of numbness around the wound but negligible. Conclusion: PCL and PLS reconstruction using bilateral hamstring autografts was considered as a good treatment method with minimal contralateral harvest site morbidity.

• Clinics in Shoulder and Elbow
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• v.6 no.1
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• pp.55-66
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• 2003

Background: The purpose of this study was to evaluated results of arthroscopic treatment of the traumatic recurrent unidirectional posterior subluxation. Materials and Methods: We treated twenty-seven patients who had traumatic recurrent unidirectional posterior subluxation of the shoulder by arthroscopic labral repair and posterior capsular shift and prospectively evaluated for a mean of thirty-nine months (range,24 to 85 months). Patients who had posteroinferior instability, multidirectional instability, atraumatic onset, or revision cases were excluded. There were twenty-five male and two female patients with the mean age of twenty-one years (range, 14 to 33 years). All patients were involved in sports activity. All had a significant traumatic event prior to the onset of the instability. Stability, motion, three objective measurement (UCLA, ASES, and Rowe scores) and two subjective measurements (pain and function visual analogue scale) were evaluated. Results: The most common finding in magnetic resonance image-arthrogram was separation of the posteroinferior labrum without displacement in 9 patients, In arthroscopic examination, all patients had one or more lesions in the posterior inferior labrum and capsule. The most common finding was incomplete stripping of the posterior inferior labrum (18 patients). The posteroinferior capsule subjectively appeared to be stretched in twenty-two patients. At follow-up, all patients had improved shoulder function and scores(p < 0.01). All patients had stable shoulder by subjectivel and objectivel measurements, except one patient who had recurrent subluxation. All but one patient with postoperative recurrence were able to return to their prior sports activity with little or no limitation. Twenty-four patients were graded as having more than 90％ of shoulder function. Their were twenty-one excellent, five good, and one fair UCLA. scores. Pain sore improved from 4.5 to 0.2 point(p : 0.0001). Mean loss internal rotation was one vertebral level. None had operative complications. Conclusion: In conclusion, treatment outcomes of the traumatic unidirectional recurrent posterior subluxation are consistently reliable with respect to the stability, pain relief, and functional restoration by the arthroscopic posterior capsular shift procedure.

• The Korean Journal of Nuclear Medicine
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• v.32 no.5
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• pp.403-413
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• 1998

Purpose: We investigated reproducibility of the quantification of left ventricular volume and ejection fraction, and grading of myocardial wall motion and systolic thickening when we used gated myocardial SPECT and Cedars quantification software. Materials and Methods: We performed gated myocardial SPECT in 33 consecutive patients twice in the same position after Tc-99m-MIBI SPECT We used 16 frames per cycle for the gating of sequential Tc-99m-MIBI SPECT. After reconstruction, we used Cedars quantitative gated SPECT and calculated ventricular volume and ejection fraction (EF). Wall motion was graded using 5 point score. Wall thickening was graded using 4 point score. Coefficient of variation for re-examination of volume and fraction were calculated. Kappa values (k-value) for assessing reproducibility of wall motion or wall thickening were calculated. Results: Enddiastolic volumes (EDV) ranged from 58 ml to 248 ml (122 ml +/- 42 ml), endsystolic volumes (ESV) from 20 ml to 174 ml (65 ml +/- 39 ml), and EF from 20% to 65% (51% +/- 14%). Geometric mean of standard deviations of 33 patients was 5.0 ml for EDV, 3.9 ml for ESV and 1.9% for EF. Their average differences were not different from zero (p>0.05). k-value for wall motion using 2 consecutive images was 0.76 (confidence interval: 0.71-0.81). k-value was 0.87 (confidence interval: 0.83-0.90) for assessment of wall thickening. Conclusion: We concluded that quantification of functional indices, assessment of wall motion and wall thickening using gated Tc-99m-MIBI SPECT was reproducible and we could use this method for the evaluation of short-acting drug effect.