• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.47-53
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• 2003

자발착화연소법과 분무열분해법을 동시에 적용한 초음파분무연소법을 이용하여 40~50nm 크기를 갖는 결정성 ZnO 분말을 합성하였다. 또한 바리스터로의 응용을 위해 Bi, Sb, Co, Mn을 초기출발원료인 Zn-nitrate에 첨가하여 복합조성의 ZnO계 바리스터 분말을 합성하였다. 합성된 바리스터의 분말을 성형 및 소결하여 전기적 특성을 관찰한 결과 Co를 첨가한 분말보다 Mn을 첨가한 분말에서 우수한 전기적 특성을 나타내었다.

• Proceedings of the Korea Society for Simulation Conference
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• 2000.11a
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• pp.67-72
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• 2000

PET는 합성섬유, 필름, 음료수병, 성형 플라스틱 등의 다양한 용도를 가지고 있으며 특히 섬유 원료부분에서는 전세계의 약 40%이상을 차지하고 있는 상업적 입장에서 아주 중요한 소재이다.［1］그러나, PET 제조공정은 긴 반응시간과 높은 반응온도, 대용량의 다단계 공정시설을 필요로 하는 대표적인 에너지 다소비 공정으로서 현대의 치열한 고분자 제품의 시장경쟁 상황에서 에너지 투입량 감축을 위한 공정의 해석 및 개발과 그로 인한 생산원가의 절감이 필수적이다. 본 연구에서는 실제 공장에서 사용되는 단일 연속식 직접 에스테르화 반응기(CSTR Direct Esterification Reactor)를 모델링하고 Van Krevelen［2］의 Group contribution method로 계산된 올리고머의 열용량값을 이용하여 에너지 소모량을 계산하였다. 모델링 결과는 모두 실제 공장의 자료와 비교되었으며 가장 제어하기 쉬운 변수에 따른 반응물의 물성과 에너지 소모량을 분석하였다. 또한 압력이 일정한 조건 하에서 입력변화에 따른 반응기의 동적 모델링을 동시에 수행하였으며 투입에너지량과 반응기의 운전지표와의 관계를 분석하였다. 이러한 연구는 실제 공정분석과 최적화에 있어서 소모 에너지량을 고려한 보다 정확한 지표를 제시하고 에너지 사용의 효율성을 높이는 데 기여할 수 있다.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1991.06a
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• pp.43-43
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• 1991

부비동 점액낭종은 주로 전두동과 사골동에 발생하며 점차 커져서 인접 기관에 영향을 미치기도 한다. 저자들은 1985년 1월부터 1991년 3월까지 충남대학교병원 이비인후과에서 부비동 점액낭종으로 수술받았던 15예를 대상으로 임상분석을 실시하여 다음과 같은 결과를 얻었다. 성별은 남자 6예 여자 9예였고, 연령은 17세에서 79세까지였으며 50대에서 5예로 가장 많았다. 병변부위로는 사골동에 국한된 경우가 7예로 가장 많았고, 전두동과 사골동을 동시에 침범한 경우가 4예, 전두동에 국한된 경우가 2예, 사골동과 접형동을 침범한 경우가 1례였다. 안증상은 11예에서 있었으며 그중 안구돌출이 7예로 가장 많았고, 시력감퇴 6예, 안구운동장애 4예 등이었다. 5예에서 두개저 파괴로 인한 경막의 노출이 있었다. 치료는 사골동 비외수술법이 7예로 가장 많았고, Lynch operation 4예, 골성형 전두동수술 2예, Lateral rhinotomy를 통한 배액 1예, Midfacial degloving approach를 통한 배액이 1예였다.

• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.86-88
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• 2004

본 연구에서는 고주파 이동통신 기기용 칩형 세라믹 안테나의 사용을 위한 저유전율 및 저온동시소성이 가능한 CaO-B2O3-SiO2계 유리를 제조하고자 하였다. 제조된 CaO-B2O3-SiO2계 유리는 열분석을 통하여 낮은 연화온도를 갖는 안정한 유리조성을 선정하였다. 유리분말을 이용하여 성형된 샘플은 소결온도에 따른 특성을 조사하였다. 소결온도변화에 따라 유전율(${\epsilon}_r$)은 4-4.5값을 나타냈으며, 유전손실(tan$\delta$)은 <$0.1\%$ 보였으나, 품질계수(Q$\times$f)는 큰 변화폭을 보였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.326-326
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• 2012

현재 자동차 강판 시장은 이산화탄소 저감과 승객의 안전확보를 위하여 고장력강을 요구하고 있는 추세이며, 강도와 성형성을 동시에 확보하기 위하여 DP, TRIP강과 같은 변태강화형 강판을 선호한다. 그러나 강판의 상분율을 제어하기 위해서는 Si, Mn등과 같은 합금원소를 필요로 하게 되며 강판의 생산공정 중 이들 합금원소는 강판의 표면에 산화물로 농화되어 아연도금 특성을 크게 저하시키는 결과를 초래한다. 따라서 본 연구에서는 냉연 아연도금강판의 생산 공정을 모사하고 이들의 산화물 구조를 분석하여 도금특성에 어떠한 영향을 미치는지 고찰하고 Ni-precoating 공정을 이용하여 강판의 도금성 개선의 가능성을 제시하였다.

• The korean journal of orthodontics
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• v.38 no.2
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• pp.104-120
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• 2008

Purpose: The purpose of this study was to assess the hard and soft tissue changes associated with mandibular bilateral sagittal split osteotomy and genioplasty. Methods: This is a retrospective study of 40 patients who underwent either bilateral sagittal split osteotomy for mandibular setback (BSSO group, n = 20) or in combination with advancement genioplasty (Genio group, n = 20). Lateral radiographs, were taken before and immediately after surgery, and at least 6 months after surgery. Results: Comparing hard and soft tissue changes between the BSSO group and Genio group, there were significant differences in the lower incisor, soft tissue B point (B'), and soft tissue Pogonion (Pg') (p < 0.5). The mean ratio of hard and soft tissue changes for B/B', Pg/Pg', and Menton/soft tissue Menton after surgery in the BSSO group was 0.997, 0.965, and 1.022 respectively, and 0.824, 0.602, and 0.887 respectively in the genio group. Significant differences were found between the two groups. There were significant differences in lip thickness (B-B', Pg-Pg') in the Genioplasty group between pre and postsurgery, but not in the BSSO group. Pogonion to Labrale inferior and B' had a correlation coefficient of 0.833, 0.922, respectively for the BSSO group, and 0.775, 0.799 for the Genio group. Conclusions: The results indicate that there is a significant difference between bilateral sagittal split osteotomy with or without genioplasty in the lower facial esthetics values. The combination of mandibular setback and genioplasty had a smaller change in soft tissue thickness of the symphysis area after surgery than that of mandibular setback only.

• Archives of Craniofacial Surgery
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• v.10 no.2
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• pp.86-90
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• 2009

Purpose: Inferior blow-out fracture is the common facial fracture. Unsatisfactory functional and aesthetic outcomes are frequent when it is treated inappropriately. If fractures are extended and reach the posterior end of orbital floor, enophthalmos frequently followed as complication. The purpose of this study was to evaluate reduction technique of extensive inferior blow-out fracture with ballooning of foley catheter through endoscopic transnasal approach and implantation of $Medpor^{(R)}$ through subciliary approach. Methods: A retrospective study was performed on 14 patients with extensive inferior blow-out fracture who underwent ballooning of foley catheter through endoscopic transnasal approach with implantation of $Medpor^{(R)}$ through subciliary approach. Patients were operated from May 2005 to November 2007. Data for 14 patients were acquired from patient's charts. Preoperative and postoperative data for enophthalmos, diplopia, limitation of extraocular motion were reviewed. Preoperative and postoperative CT scan were also checked. The patients were followed up from 4 to 18 months. Results: The enophthalmos was corrected in all patients. Among 7 patients with diplopia preoperatively, diplopia was resolved in three patients postoperatively. The diplopia persisted in four patients and two of them also had limitation of extraocular motion postoperatively. The limitation of extraocular motion occurred in seven patients preoperatively. But five patients recovered after operation immediately. These symptoms were resolved about three months after the operation. Conclusion: The ballooning of foley catheter through endoscopic transnasal approach with implantation of $Medpor^{(R)}$ through subciliary approach can be considered one of the appropriate technique for extensive inferior blowout fracture.

• Archives of Craniofacial Surgery
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• v.11 no.2
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• pp.77-84
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• 2010

Purpose: The nasal bones are the most common fracture sites of the facial bones, and a careful reduction may still result in secondary deformities, such as saddle nose, deviated nose, hump nose etc, requiring secondary cosmetic rhinoplasty. Therefore, this study examined the clinical characteristics of nasal bone fractures to propose guidelines for patient selection and surgical procedures to achieve more satisfactory results and to prevent secondary deformities with simultaneous augmentation rhinoplasty and bony reduction. Methods: The study was based on 26 out of 149 nasal bone fracture patients who underwent simultaneous augmentation rhinoplasty with bony reduction between May 2008 and April 2009. Retrospective analysis was performed according to the clinical data, surgical techniques and postoperative results. Results: Of the 26 patients, there were 15 males and 11 females. The incidence according to the Stranc's classification revealed that 62% of patients were injured by a frontal impact and 38% by a lateral impact. Frontal impact plane I (50%) was the most frequent type. At the follow up, 18 (81.2%) out of 22 patients were satisfied with their postoperative outcome, and the remaining 4 patients were fair. No one was dissatisfied. However, 5 cases in 3 patients (23%) had some complications; minimal implant deviation in 2 cases, minor irregularity on the nasal dorsum in 2 cases and palpable implant movement under palpation in 1 case. None of these cases required surgical correction. Conclusion: With the proper guidance, simultaneous augmentation rhinoplasty with bony reduction can prevent secondary deformities and satisfy the cosmetic outcomes.

• Archives of Craniofacial Surgery
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• v.11 no.2
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• pp.91-94
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• 2010

Purpose: For the best possible aesthetic reconstruction after craniofacial bone tumor resection, pasteurization has been adopted to devitalize neoplastic cells while maintaining osteoinductive properties and mechanical strength. This case report aims to demonstrate a long-term follow-up result of a monostotic fibrous dysplasia in frontal bone which was reconstructed by pasteurized tumoral autograft in situ. Methods: A 14-year-old girl presented with a hard, nontender, slowly growing mass of 6-year duration on her left supraorbital area. CT showed $5{\times}4{\times}3cm$ sized well defined bony mass confined to frontal bone with heterogeneous density. Tumor was excised completely through bicoronal approach and reimplanted to its original site after pasteurization at $60^{\circ}C$ for 30 minutes. The pathologic examination confirmed fibrous dysplasia. Results: She revisited our clinic 5 years later after suffering some assault on her face. On CT examination, pasteurized tumoral autograft was incorporated to host bone except the fractured upper orbital rim without any evidence of recurrence. She has been satisfied with the result. Conclusion: Pasteurization offers a simple, reliable, cosmetic, economic, and durable reconstruction method for craniofacial skeletal tumor. It has advantages of both biologic incorporation ability and mechanical strength without risk of recurrence. So, it should be considered as one of the primary options in benign as well as resectable malignant tumors of craniofacial skeleton.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.1
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• pp.76-87
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• 2000

Multicarrier DS-CDAM is an effective approach to realize wideband CDMA system in a multipath fading channeal. In this paper, we propose a cinvolutionally-coded overlapped multicarrier DS-CDMA system, and show the performance improvement by comparing with conventional multicarrier DS-CDMA system. We consider the case of 50% overlapping with the adjacent subband to utilize the transmission bandwidth more efficiently. In the proposed multicarrier system, each of the rate 1/M convolutionally-encoded symbols is also 1/R repetition coded and transmitted using overlapped multicarriers and we may obtain the coding gain and frequency diversity effect, simultaneously. We also analyze the possibility of reduction in total MUI by considering a raised-cosine wave-shaping filter having a roll-off factor (0< ${\beta}{\le}1$). It will be shown that the proposed system outperforms the multicarrier DS-CDMA system in $^{[3]}$.