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Al 7050 단조품 표면의 입도성장층 방지에 관한 연구
이정환,이상용,이영선,Lee, Jeong-Hwan,Lee, Sang-Yong,Lee, Yeong-Seon 한국기계연구원 1996 硏究論文集 Vol.26 No.-
Age hardenable aluminium alloys show high specific strength, good thermal and electrical conductivity as well as lightness, and are typical aircraft materials. High fatigue strength and good resistancy against stress corrosion cracking are also important for aircraft aluminium alloys. Al alloy 7050 has been developed to meet the above mentioned requirements and the use of this alloy as forged aircraft part becomes more important. However, forged 7050 parts showed undersiable structures such as severe local grain coarsening in surface area and unproper metal flow that is degrading mechanical properties. In this paper, microstructural aspects of die forging in the Al alloy 7050 are investigated. Also suggested are the optimal forging conditions for microstructural control of Al alloy 7050.
A Case of Metastatic Eccrine Porocarcinoma with a Review of the Literatures
이정환,임주한,김루시아,김철수,이현규,나소연,김성현,정지중,이명동,예재호,이문희,Lee, Jung-Hwan,Lim, Joo-Han,Kim, Lucia,Kim, Chu-Soo,Yi, Hyeon-Gyu,Nah, So-Yun,Kim, Seong-Hyun,Jeong, Ji-Joong,Lee, Myung-Dong,Ye, Jea-Ho,Lee, Moon-Hee The Korean Society for Head and Neck Oncology 2011 대한두경부 종양학회지 Vol.27 No.2
에크린 한공암종은 흔하지 않으며, 전이성 에크린 한공암종은 매우 드문 암이다. 에크린 한공암종은 표피내 한관에서 기원하는 피부 부속기 악성 종양으로, 대부분 에크린 한공암종은 항암치료와 방사선치료에 효과가 없으며, 따라서 유일한 치료방법은 전이되기 전에 국소 및 광범위 절제술을 시행하여야 한다. 본 환자는 두피에 발생한 에크린 한공암종이 점점 진행하여 피부, 림프절, 폐 등으로 전이하였고, 다수의 광범위 절제술에 이어 항암치료와 방사선치료를 받았지만, 결국 폐전이가 악화되어 사망하였다. 본 저자들은 항암치료와 방사선치료에 불응한 에크린 한공암종 1예를 치료에 대한 문헌고찰과 더불어 보고하는 바이다.
탈모증 유발요인과 한의학적 치료 효과에 대한 후향적 연구 - 후천적 열성 탈모를 중심으로 -
이정환,장진영,윤영준,조아라,신현진,정상욱,정연호,강여름,Lee, Jung-Hwan,Jang, Jin-Young,Yoon, YoungJoon,Cho, Ah-Ra,Shin, Hyun-Jin,Jung, Sang-Uk,Jeong, Yeon-Ho,Kang, Yeo-Reum 대한한방안이비인후피부과학회 2013 한방안이비인후피부과학회지 Vol.26 No.2
Objectives : The purpose of this study is to report the causes and the effects of korean medicine treatment on alopecia. Methods : 1050 patients with alopecia, who had visited oriental medical clinics from July 2011 to October 2012, were analyzed by self-assessments. And 153 patients of them were treated with korean medicine treatment for 3 months. Treatment results were evaluated by patients' self-assessments and global & enlarged photographic reviews. Results : 1. The gender ratio of male to female was 2:1 and most patients belonged to the 20~30 year old group. 2. Family history of baldness in alopecia patients was a total of 57.3%, paternal 44.4% and maternal 21.2%. 3. Subjective symptoms of fever in parietal region was a total of 97.4% in alopecia patients. 4. After 1 month treatment, the fever in the parietal region was decreased by 37.3% of patients. And their subjective hair loss was also significantly decreased. 5. After 3 months of treatment, the global photographic review was improved by 56.2% of the patients and the enlarged photographic review was significantly improved by 5.2% in patients' total hair count. Conclusions : A significant number of alopecia patients were young and less relative in genetic alopecia causes was less relevant than the past. Recent causes of alopecia were more concerned with the fever in parietal region. According to that reason, cooling effect korean medicine treatment was expected to be effective for febrile alopecia, and actually had significant effects on this study. For future studies, it's long term treatment and follow up studies are needed.
재발하였거나 수술적 제거가 불가능한 뇌수막종에 대한 Hydroxyurea 치료 - Preliminary Report -
이정환,김오룡,김성호,배장호,최병연,조수호,Lee, Jeong-Hwan,Kim, Oh-Lyong,Kim, Seong-Ho,Bae, Jang-Ho,Choi, Byung-Yon,Cho, Soo-Ho 대한신경외과학회 2001 Journal of Korean neurosurgical society Vol.30 No.1
1988년 1월부터 1997년 12월까지 본 교실에 내원하여 뇌수막종으로 진단받고 수술요법을 실시한 87례 중, 완전제거 후 재발한 경우와 부분적 절제후 방사선 치료를 받은 4례를 대상으로 hydroxyurea를 이용해 치료한 결과를 분석하였다. 남자가 1례, 여자가 3례이었으며 연령 분포는 23세에서 55세였다. 조직학적으로 3례가 meningothelial type이었으며 1례는 angiomatous type이었다. 3례에서 소뇌교각부에 발생하였으며 1례에서 해면정맥동에 발생하였다. 모든 환자들은 수술적 치료를 시행받았으며 3례의 환자에서 방사선 치료를 시행하였다. Hydroxyurea를 20mg/kg/day용량으로 투여하였으며 평균 추적관찰기간은 34개월이었다. 치료기간중 4례에서 종양이 줄어든 예는 없었으나 종양이 성장하지는 않았다. 삼차신경통 증상이 있던 1례는 증상 호전 되었으며 수술적 치료를 3차례 받았던 1례에서 두개골절제부위에 팽창되어 있던 뇌는 축소되어 두개강내로 복귀되었다. 혈액학적 부작용으로 백혈구 수치가 1례에서 감소되었으나 2주정도 복용을 중단한 후 다시 수치는 회복되었고 다른 심각한 부작용은 나타나지 않았다. 저자들은 뇌수막종 환자중, 수술후 재발한 경우와 불완전 제거를 시행한 경우 보조적 치료방법으로 hydroxyurea의 사용하여 종양크기의 감소는 없었으나 성장을 억제할 수 있었으며 앞으로 오랜 기간 추적관찰과 많은 증례에 대한 분석을 함으로써 뇌수막종 치료의 보조 방법으로 hydroxyurea를 이용할 수 있을 것으로 생각된다. Objectives : The present study was performed to analyze results of hydroxyurea treatment for unresectable and recurrent meningiomas as adjuvant chemotherapeutic agent. Material and Methods : Among 87 cases of meningioma patients who treated surgically between Jauary 1988 and December 1997 in our department, unresectable and recurrent cases were 4 cases. Histologically, 3 cases were meningothelial type, 1 case was angiomatous type. Tumor orgin was cerebellopontine angle(CPA) in 3 cases, cavernous sinus in 1 case. Three of 4 cases received radiation treatment. All patients received a daily dosage of 20mg/kg/day of hydroxyurea. Hematological monitorning was performed monthly and tumor measurement was assessed by MR imaging before treatment and every 6 months. Mean follow-up period was 34 months. Rerults : All cases showed no enlargement of tumor mass without any shrinkage. Trigeminal neuralgia in 1 case was improved and external herniation of brain on craniectomy site in 1 case was shrunken. None of the patients had any serious side effects. White blood cell count fell below $3000/{\mu}l$ in 1 case, but recovered 2 weeks later with cessation of medication. Conclusion : Hydroxyurea stopped cell growth by triggering the apoptotic cascade. Our preliminary data indicate that hydroxyurea provides adjuvant medical treatment in patients of unresectable and recurrent meningiomas
Trellis 부호 및 엔트로피 마스킹을 이용한 정보부호화 기반 워터마킹
이정환,Lee, Jeong-Hwan 한국정보통신학회 2009 한국정보통신학회논문지 Vol.13 No.12
본 논문에서는 trellis 부호 및 엔트로피 마스킹을 이용한 정보부호화 기반 워터마킹 방법에 대하여 연구하였다. 영상을 $8{\times}8$ 블록으로 중복되지 않게 나누어 DCT 변환을 수행하고 각 블록으로부터 16개의 중간주파수 대역의 계수를 추출한다. 이를 trellis 부호화의 각 단계에서 평균이 0이고 분산이 1인 가우시안 난수와 비교하여 선형상관계수 및 왓슨거리의 선형결합이 최소인 벡터를 Viterbi 알고리즘으로 구하고 이를 원 영상에 삽입하여 워터마킹된 영상을 얻는다. 영상의 특성을 고려하기 위해 삽입벡터를 구할 때 엔트로피 마스킹 함수를 사용하여 선형상관계수와 왓슨거리의 가중치를 다르게 적용한다. 제안방법의 성능을 평가하기 위해 다수의 영상에 대한 평균비트오차율을 계산하여 성능을 비교하였으며, 평균비트오차율 측면에서 성능 개선이 있었다. In this paper, we study a watermarking method based on the informed coding and embedding by means of trellis code and entropy masking. An image is divided as $8{\times}8$ block with no overlapping and the discrete cosine transform(DCT) is applied to each block. Then the 16 medium-frequency AC terms of each block are extracted. Next it is compared with gaussian random vectors having zero mean and unit variance. As these processing, the embedding vectors with minimum value of linear combination between linear correlation and Watson distance can be obtained by Viterbi algorithm at each stage of trellis coding. For considering the image characteristics, we apply different weight value between the linear correlation and the Watson distance using the entropy masking. To evaluate the performance of proposed method, the average bit error rate of watermark message is calculated from different several images. By the experiments the proposed method is improved in terms of the average bit error rate.