• Journal of Biosystems Engineering
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• 제18권1호
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• pp.15-20
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• 1993

Wearness has been a major failure criterion in Korean-made rotary blade. However, few studies have been conducted to improve it. In this study, the fundamental data obtained from the measurement of wearness and failure of rotary blade were analyzed to provide a guideline for the design of rotary blades. For the straight part(about 20-23 em from bolt hole) from the bolt hole to bending point of rotary blade, modifications were proposed for improvements, however, for the portion from bending point to tip was made no design recommendations because the failure behavior of that portion was difficult to analyze with the experimental data. The results are summarized as follows. 1. The current V-shape section has to be moved about 5 em toward the bending point of rotary blade. 2. The section modulus at the portion about 5-7 em distant from bolt hole has to be increased about 15-20 %. 3. The V-shape section has to be changed into U-shape to reduce the on account of recieving initial stress in blades. 4. The radius of curvature of the neck(the portion about 5-7 cm apart from bolt hole) has to be made larger to decrease the stress concentration.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.152-157
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• 2009

Titanium alloy sheets have excellent specific strength and corrosion resistance as well as good performance at high temperature. Recently, titanium alloys are widely employed not only aerospace parts but also bio prothesis and motorcycle. But the database is insufficient of the titanium alloy for press forming process. In this study, the effect of temperature on the forming limit diagram was investigated for Ti-6Al-4V titanium alloy sheet through the Hocker's punch stretching test at elevated temperature. Experimental results obtained in this study can provide a database for development of press forming process at elevated temperature of Ti-6Al-4V titanium alloy sheet. From the experimental studies it can be concluded that the formability of Ti-6Al-4V titanium alloy sheet is governed by the ductile failure for the testing temperature below and vice versa neck-induced failure above the recrystalization temperature $0.5T_m$. The formability of Ti-6Al-4V titanium alloy sheet at $750^{\circ}C$ increases about 7 times compared with that at room temperature.

• 대한방사선기술학회지:방사선기술과학
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• 제45권5호
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• pp.439-448
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• 2022

The purpose of this study was to analyze the results from statistical process control (SPC) to recommend upper and lower control limits for planning parameters based on delivery quality assurance (DQA) results and establish our institutional guidelines regarding planning parameters for helical tomotherapy (HT). A total of 53 brain, 41 head and neck (H & N), and 51 pelvis cases who had passing or failing DQA measurements were selected. The absolute point dose difference (DD) and the global gamma passing rate (GPR) for all patients were analyzed. Control charts were used to evaluate upper and lower control limits (UCL and LCL) for all assessed treatment planning parameters. Treatment planning parameters were analyzed to provide its range for DQA pass cases. We confirmed that the probability of DQA failure was higher when the proportion of leaf open time (LOT) below 100 ms was greater than 30%. LOT and gantry period (GP) were significant predictor for DQA failure using the SPC method. We investigated the availability of the SPC statistic method to establish the local planning guideline based on DQA results for HT system. The guideline of each planning parameter in HT may assist in the prediction of DQA failure using the SPC statistic method in the future.

• 대한두경부종양학회지
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• 제12권1호
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• pp.26-31
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• 1996

Radiation therapy in T1 glottic cancer offers an excellent cure rate with preservation of voice. From 1983 to 1992 eighty nine patients with TNM staged T1N0M0 invasive squamous cell carcinoma of the glottis were treated at the Dept. of Radiation Oncology, Yonsei Cancer Center, Yonsei University. There were 84 men and 5 women with median age of 59 years. All patients were treated either with Co-60 teletherapy unit or 4MV linear accelerator with an median dose of 6400 cGy(6000-7000 cGy), 200 cGy per day, 5 days in a week. Fourteen local failures have been observed and the median time to local recurrence was 17 months. There were no nodal failure without local recurrence or distant metastases. The 5 year local control rate was 84.3%. The 5 year actuarial surivival rate and the 5 year disease free survival rate were 89.2%, 87.5%, respectively. The 5 year actuarial survival rate and the 5 year disease free survival rate of the nineteen patients with anterior commissure involvement were 77.8% and 74.5% which were lower than those of seventy patients without anterior commissure involvement(91.6%, 90.6%)(p < 0.05). Among the several influencing factors, anterior commissure involvement was the significant prognostic foctor. Final local control rate, taking into account the salvage surgery, was 89.9% at 5 years.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제26권4호
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• pp.391-395
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• 2000

Malignant tumors of the maxilla represent about 3-4% of head and neck malignant neoplasm and the origins are maxillary gingiva, hard palate and maxillary sinus. We are to investigate clinical features and results according to various treatment modalities of maxillary malignant tumor to get information for better treatment results. Sixty patients with malignant maxillary tumors treated at Yonsei medical center from 1992 to 1997 were studied retrospectively. They are evaluated according to clinical signs & symptoms, stages at first diagnosis, primary site, histopathologic features, treatment method, recurrence and survival rate with clinical records, biopsy results and CT radiograph. The most common primary site was maxillary sinus and most common histopathology was squamous cell carcinoma. The local recurrence rate was 18% at 5 years, neck failure was 3% and distant metastasis was 18%. Overall survival rate was 78% at 2 years and 69% at 5 years. Failure at primary site is the main problem in the curative treatment. So, to improve survival in these patients efforts should be directed toward improvement of local control.

• The Journal of Advanced Prosthodontics
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• 제7권6호
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• pp.423-430
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• 2015

PURPOSE. To evaluate the cumulative survival rate (CSR) and mechanical complications of single-tooth $Ankylos^{(R)}$ implants. MATERIALS AND METHODS. This was a retrospective clinical study that analyzed 450 single $Ankylos^{(R)}$ implants installed in 275 patients between December 2005 and December 2012. The main outcomes were survival results CSR and implant failure) and mechanical complications (screw loosening, fracture, and cumulative fracture rate [CFR]). The main outcomes were analyzed according to age, sex, implant length or diameter, bone graft, arch, and position. RESULTS. The 8-year CSR was 96.9%. Thirteen (2.9%) implants failed because of early osseointegration failure in 3, marginal bone loss in 6, and abutment fracture in 4. Screw loosening occurred in 10 implants (2.2%), and 10 abutment fractures occurred. All abutment fractures were located in the neck, and concurrent screw fractures were observed. The CSR and rate of screw loosening did not differ significantly according to factors. The CFR was higher in middle-aged patients (5.3% vs 0.0% in younger and older patients); for teeth in a molar position (5.8% vs 0.0% for premolar or 1.1% for anterior position); and for larger-diameter implants (4.5% for 4.5 mm and 6.7% for 5.5 mm diameter vs 0.5% for 3.5 mm diameter) (all P<.05). CONCLUSION. The $Ankylos^{(R)}$ implant is suitable for single-tooth restoration in Koreans. However, relatively frequent abutment fractures (2.2%) were observed and some fractures resulted in implant failures. Middle-aged patients, the molar position, and a large implant diameter were associated with a high incidence of abutment fracture.

• 대한의용생체공학회:의공학회지
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• 제26권2호
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• pp.123-127
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• 2005

Compression Hip Screw (CHS) is one of the most widely-used prostheses for the treatment of intertrochanteric fractures because of its strong fixation capability. Fractures at the neck and screw holes are frequently noted as some of its clinical drawbacks, which warrant more in-depth biomechanical analysis on its design variables. The purpose of this study was to evaluate changes in the strength with respect to the changes in design such as the plate thickness and the number of screw holes. Both mechanical test and FEM analysis were used to systematically investigate the sensitivities of the above-mentioned design variables. For the first part of the mechanical test, CHS (n=20) were tested until failure. The CHS specimens were classified into four groups: Group Ⅰ was the control group with the neck thickness of 6-㎜ and 5 screw holes on the side plate, Group Ⅱ 6-㎜ thick and 8 holes, Group Ⅲ 7.5-㎜ thick and 5 holes, and Group Ⅳ 7.5-㎜ thick and 8 holes. Then, the fatigue test was done for each group by imparting 50% and 75% of the failure loads for one million cycles. For the FEM analysis, FE models were made for each group. Appropriate loading and boundary conditions were applied based on the failure test results. Stresses were assessed. Mechanical test results indicated that the failure strength increased dramatically by 80% with thicker plate. However, the strength remained unchanged or decreased slightly despite the increase in number of holes. These results indicated the higher sensitivity of plate thickness to the implant strength. No fatigue failures were observed which suggested the implant could withstand at least one million cycles of fatigue load regardless of the design changes. Our FEM results also supported the above results by showing a similar trend in stress as those of mechanical test. In summary, our biomechanical results were able to show that plate thickness could be a more important variable in design for reinforcing the strength of CHS than the number of screw holes.

• Radiation Oncology Journal
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• 제20권1호
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• pp.17-23
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• 2002

목적 : 국한성 두경부 혈관 중심위 림프종에서 화학방사선 병용치료법과 방사선치료 단독요법의 치료성적을 비교하여 화학방사선 병용치료법의 임상적 유용성 여부를 알아보고자 하였다. 대상 및 방법 : 1976년부터 1995년까지 연세암센타에서 병기 I, II기의 두경부 혈관 중심위 림프종으로 치료받은 143 예를 대상으로 하였다. 방사선치료단독(104예)의 경우 20~70 Gy (중앙값 50.4 Gy)를 병소 부위에 국소적으로 조사하였고 화학방사선 병용치료(39예)의 경우에는 1~6회(중앙값 3회)의 화학요법을 시행한 후 병소 부위에 국소적으로 방사선치료를 시행하였다. 치료방법에 따른 반응율, 치료실패양상, 후유증, 생존율 등을 비교하여 보았다. 결과 : 치료에 대한 높은 반응율에도 불구하고 국소치료실패가 치료실패양상의 가장 흔한 원인이었고 화학요법의 시행에 따른 치료실패양상의 변화는 없었다. 치료방법에 따른 환자들의 순응도에는 차이가 없었으나 혈구포식세포 증후군(hemophagocytic syndrome), 패혈증, 난치성 출혈(intractable bleeding), 2차 암(new primary cancer) 등의 발생 빈도는 화학방사선 병용치료법을 시행한 경우에 방사선치료 단독요법을 시행한 경우보다 높은 경향을 나타냈다. 방사선 단독으로 치료한 경우의 5년 생존율과 무병 생존율은 각각 38%와 32%로 저조하였고 화학요법의 시행에도 생존율의 향상은 없었다. 완전관해 여부가 단변량과 다변량 분석에서 가장 중요한 예후인자이었고 화학요법의 병용 여부는 생존율에 영향을 미치지 못했다. 결론 : 국한성 두경부 혈관 중심위 림프종의 치료에서 화학방사선 병용치료법이 방사선치료 단독요법보다 유용하다는 사실이 입증되지 못하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제13권9호
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• pp.4469-4475
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• 2012

Background: The potential use of hypomethylation of Long INterspersed Element 1 (LINE-1) and Alu elements (Alu) as a biomarker has been comprehensively assessed in several cancers, including head and neck squamous cell carcinoma (HNSCC). Failure to detect occult metastatic head and neck tumors on radical neck lymph node dissection can affect the therapeutic measures taken. Objective: The aim of this study was to investigate the LINE-1 and Alu methylation status and determine whether it can be applied for detection of occult metastatic tumors in HNSCC cases. Methods: We used the Combine Bisulfite Restriction Analysis (COBRA) technique to analyse LINE-1 and Alu methylation status. In addition to the methylation level, LINE-1 and Alu loci were classified based on the methylation statuses of two CpG dinucleotides in each allele as follows: hypermethylation ($^mC^mC$), hypomethylation ($^uC^uC$), and 2 forms of partial methylation ($^mC^uC$ and $^uC^mC$). Sixty-one lymph nodes were divided into 3 groups: 1) non-metastatic head and neck cancer (NM), 2) histologically negative for tumor cells of cases with metastatic head and neck cancer (LN), and 3) histologically positive for tumor cells (LP). Results: Alu methylation change was not significant. However, LINE-1 methylation of both LN and LP was altered, as demonstrated by the lower LINE-1 methylation levels (p<0.001), higher percentage of $^mC^uC$ (p<0.01), lower percentage of $^uC^mC$ (p<0.001) and higher percentage of $^uC^uC$ (p<0.001). Using receiver operating characteristic (ROC) curve analysis, $%^uC^mC$ and $%^mC^uC$ values revealed a high level of AUC at 0.806 and 0.716, respectively, in distinguishing LN from NM. Conclusion: The LINE-1 methylation changes in LN have the same pattern as that in LP. This epigenomic change may be due to the presence of occult metastatic tumor in LN cases.

• 대한두경부종양학회지
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• 제12권1호
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• pp.92-99
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• 1996

The primary treatment of the nasopharyngeal carcinoma is at this time, mainly based on radiotherapy. In most studies for patient treated with radiotherapy, overall 5-year survival rate is in the range of 35 to 55%. Obviously, these therapeutic results may be influenced by various factors such as clinical stages, histopathological types and radiation techniques, etc. Though the radiotherapy had a good therapeutic result, there is a limitation to apply the radiotherapy only in cases of the advanced nasopharyngeal carcinoma. Anatomical complexity of the skull base and difficulties in complete surgical intervention were the trouble of the surgery but in the case of radiation failure, there is no adequate choice of other curative modalities. So it is appropriate to investigate whether surgical resection may improve the outcome of treatment of nasopharyngeal carcinoma. The purpose of this papaer is to report our surgical experience of the nasopharyngeal carcinoma, then to take into consideration of the new model of treatment strategy of nasopharyngeal carcinoma.