• Journal of the Korean Data and Information Science Society
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• v.25 no.2
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• pp.327-336
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• 2014

Recurrent event data occurs when a subject experiences same type of event repeatedly and is found in various areas such as the social sciences, Economics, medicine and public health. To analyze recurrent event data either a total time or a gap time is adopted according to research interest. In this paper, we analyze recurrent event data with incomplete observation gap using a gap time scale. That is, some subjects leave temporarily from a study and return after a while. But it is not available when the observation gaps terminate. We adopt an interval censoring mechanism for estimating the termination time. Furthermore, to model the association among gap times of a subject, a frailty effect is incorporated into a model. Programs included in Survival package of R program are implemented to estimate the covariate effect as well as the variance of frailty effect. YTOP (Young Traffic Offenders Program) data is analyzed with both proportional hazard model and a weibull regression model.

• Journal of the Korean Society of Radiology
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• v.79 no.5
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• pp.264-270
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• 2018

Purpose: To evaluate the effect of portal hypertension on the tumor recurrence in patients with hepatocellular carcinoma (HCC) and without hepatic decompression following radiofrequency ablation (RFA). Materials and Methods: Treatment-naïve HCC patients within the Milan criteria and with Child-Pugh class A were included in this study, who had performed RFA in our hospital between January 2010 and March 2017. Univariate and multivariate analyses using the Cox proportional hazard model were performed to find the predictors of local or distant tumor recurrence. Results: Overall, 178 patients were included in this study. Median follow-up period was 40.2 months. The difference in the local tumor progression rates depending on the absence or presence of portal hypertension was not statistically significant (p = 0.195). The 1-, 3-, and 5-year distant intrahepatic tumor spread rates were 6.6%, 29.5%, and 537% in patients without portal hypertension, and 23.4%, 51.9%, and 63.6% in patients with portal hypertension, respectively. The difference was statistically significant (p = 0.011). Univariate and multivariate analysis showed that portal hypertension was an independent predictor for distant intrahepatic tumor spread (p = 0.008). Conclusion: For HCC patients with Child-Pugh class A, portal hypertension adversely affected distant intrahepatic tumor progression.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.2083-2099
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• 1991

An experiment has been carried out to investigate the aerodynamic effect of surface roughness on the characteristics of the turbulent separation and reattaching flow downstream of a backward-facing step. The distributions of boundary layer parameters, forward-flow fraction and turbulent stresses in the region near the reattachment point are measured with a split film sensor. It is demonstrated that the streamwise distributions of the forward-flow fraction in the recirculation and reattachment regions are similar, independent of the roughness. The reattachment length is found to be only weakly affected by the roughness. It is also shown that the velocity profile on the rough surface approaches to that of the equilibrium turbulent boundary layer faster than that on the smooth surface in the redeveloping region after reattachment.

• Journal of Oral Medicine and Pain
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• v.32 no.1
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• pp.81-90
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• 2007

The life changes of TMJ patients were evaluated through the Social Readjustment Rating Scale (SRRS) questionnaire. 33 recurred TMD patients and 32 new TMD patients were studied at the TMJ clinics, Department of Oral Medicine, PNUH from September 2005 to August 2006. The obtained results were as follows: 1. The life change unit(LCU) totals in the recurred TMD patients were significantly higher than those in the control subjects, during the $7{\sim}12$ months before presentation for the hospital. 2. The life change unit(LCU) totals in the recurred TMD patients were higher a little than those in the control subjects during a year before presentation for the hospital. 3. There was no significant difference in LCU totals and life events between the recurred TMD patients and the control subjects by age. 4. There was no significant difference in LCU totals and life events between the married group and unmarried group in the subjects.

• Radiation Oncology Journal
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• v.24 no.4
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• pp.255-262
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• 2006

$\underline{Purpose}$: To evaluate the pathological prognostic factors related to local recurrence after radical surgery and adjuvant radiation therapy in advanced rectal cancer. $\underline{Materials\;and\;Methods}$: Fifty-four patients with advanced rectal cancer who were treated with radical surgery followed by adjuvant radiotherapy and chemotherapy between February 1993 and December 2001 were enrolled in this study. Among these patients, 14 patients experienced local recurrence. Tissue specimens of the patients were obtained to determine pathologic parameters such as histological grade, depth of invasion, venous invasion, lymphatic invasion, neural invasion and immunohistopathological analysis for expression of p53, Ki-67, c-erb, ezrin, c-met, phosphorylated S6 kinase, S100A4, and HIF-1 alpha. The correlation of these parameters with the tumor response to radiotherapy was statistically analyzed using the chi-square test, multivariate analysis, and the hierarchical clustering method. $\underline{Results}$: In univariate analysis, the histological tumor grade, venous invasion, invasion depth of the tumor and the over expression of c-met and HIF-1 alpha were accompanied with radioresistance that was found to be statistically significant. In multivariate analysis, venous invasion, invasion depth of tumor and over expression of c-met were also accompanied with radioresistance that was found to be statistically significant. By analysis with hierarchical clustering, the invasion depth of the tumor, and the over expression of c-met and HIF-1 alpha were factors found to be related to local recurrence. Whereas 71.4% of patients with local recurrence had 2 or more these factors, only 27.5% of patients without local recurrence had 2 or more of these factors. $\underline{Conclusion}$: In advanced rectal cancer patients treated by radical surgery and adjuvant chemo-radiation therapy, the poor prognostic factors found to be related to local recurrence were HIF-1 alpha positive, c-met positive, and an invasion depth more than 5.5 mm. A prospective study is necessary to confirm whether these factors would be useful clinical parameters to measure and predict a radio-resistance group of patients.

• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.239-249
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• 1999

In orthognathic surgery to obtain proper functional and esthetic form after skeletal discrepancy treatment, precise diagnosis and treatment plan are essential. Especially in two jaw surgeries that have serious upper and lower jaw problems, maxilla and mandible are arranged in three dimensions. Based on the maxillary rearrangement, mandibular sagittal and transverse positions are determined, and thus new occlusal plane is established. The object of this study is to evaluate the stability of the indiviual ideal occlusal plane based on the architectural and structural craniofacial analysis of Delaires. The subjects of this study were 48 patients who underwent two jaw surgeries, and they were equally divided into two groups, A and B. A group was operated with ideal occlusal plane and B group was not. Two groups were compared at the preoperative, immediate postoperative (average 4.3days), and long-term postoperative (average 1.3years) lateral cephalometric radiographs. The following results were obtained: 1. ANS was lower than that of PNS for both A and B after the surgery. That is, maxilla and mandible are rotated in posterior and superior direction. 2. Significances were found between $T_2$ and $T_3$ for both A and B are HRP-Me at vortical measurements, articular angle(p<0.01), gonial angle(p<0.01), and Mn. plane angle(p<0.05) at angular measurement. Mn. plane angle is increased at HRP-Me is decreased for both A and B. 3. There is no significance in skeletal stability aster the surgery between group A and B. 4. Horizontal movements of B and Pog by surgery have statistically significant inverse correlations with horizontal relapse of B and Pog, and vertical relapse of PNS, as well as Mn. Plane angle, and gonial angle after the surgery.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5094-5101
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• 2011

In order to investigate recurrence rate and risk factors for recurrence of gastric cancer after curative resection, we examined blood biochemical profile and clinicopathological features of 386 gastric cancer patients by using medical charts and data of hospital cancer registry from September 2010 to May 2011. Chi-square test and logistic regression analyses were performed to identify risk factors. The recurrence rate of all gastric cancer patients was 2.6%; The recurrence rate by gender was 3.45% in male and 0.89% in female, and that was 4 times higher in male than in female. On univariate logistic regression analyses, lymph node metastases(OR=8.793), Helicobactor pylori infecton(OR=6.495), abnormal total cholesterol(OR=14.333) were related to recurrence. On multivariate logistic regression analyses, lymph node metastases and H. pylori infection were very important risk factors for recurrence of gastric cancer. In conclusion, lymph node metastases, H. pylori infection, and total cholesterol control were very important to prevent recurrence of gastric cancer, and it needs to monitor blood biochemical (C-reactive protein, carcinoembryonic antigen, etc) for the early detection of gastric cancer recurrence.

• Childhood Kidney Diseases
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• v.9 no.2
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• pp.159-166
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• 2005

Purpose : Recently the merits of 6 weeks of initial prednisolone treatment for pediatric primary nephrotic syndrome have been reported, and the use of the 6 week regimen is increasing. We compared our experiences with the 6 week treatment versus the 4 week treatment for Korean patients. Methods : We conducted a retrospective analysis of 69 children who had primary nephrotic syndrome and who were followed up for at least 12 months in the 4 major medical centers in Daegu. The remission rate, the relapse rate, the frequency of relapse and complication of steroid treatment were compared between the 4 weeks and 6 weeks treatment group. Results : Of the 69 children, 42 were in the 4 week treatment group and 27 were in the 6 week group. The median age, blood pressure, serum total protein, serum albumin, cholesterol, creatinine, estimated creatinine clearance, 24 hour urine protein and 12 month cumulative dose did not differ between the two groups. Among the children who relapsed after steroid treatment, the relapse time was significantly later for the 6 week treatment group. The relapse rate after 1 year of treatment was 62$\%$ in the 4 week treatment group and 52$\%$ in the 6 week treatment group; however, there was no statistically significant difference between the two groups. The frequency of relapse at 12 months was $1.5{\pm}1.2$ times in the 4 week treatment group and $1.1{\pm}1.2$ times in the 6 week treatment group, and there was not different between the two groups. The most common side effects of steroid treatment were an increase of appetite and a cushingoid appearance, and there was no statistical difference between the two groups. Among the 27 children who had kidney biopsies performed, 21 suffered from minimal change nephrotic syndrome. Conclusion : The first relapse time after steroid treatment was significantly later in the 6 week steroid treatment group. The frequency of relapse and the 12 month cumulative dose of steroid were lower in the 6 week treatment group, but there was no statistical significance between the two groups. The side effects of steroid treatment did not differ between the two groups. We need to study the long term side effects and the advanced regimens of steroid treatment in the future.(J Korea Soc Pediatr Nephrol 2005;9:159-166)

• Korean Journal of Head & Neck Oncology
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• v.31 no.2
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• pp.29-35
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• 2015

목적 : 국소 재발한 진행된 갑상선 유두암의 치료로 수술 후 외부방사선의 역할을 알아보고자 하였다. 대상 및 방법 : 원자력병원에서 2000년 1월부터 2012년 2월까지 사이버나이프 혹은 외부방사선 치료를 받은 수술과 방사선요오드 치료 후 국소 재발한 진행된 갑상선 유두암 환자 13 명을 대상으로 하였다. 경과관찰 기간 동안 국소 및 부위 재발이 발생환 환자는 6 명이었다. 몇몇의 위험인자를 찾기 위해서 Kaplan-Meier method와 log-rank test를 이용하여 성별, 종양단계, 방사선 치료 전 수술 횟수, 방사선요오드치료 횟수, 수술 후 잔존 암의 여부, 원격전이에 대해 단변량 분석하였다. 결과 : 방사선 치료 후 평균 추적관찰기관은 53.8개월(범위, 36 ~ 108개월)이고 그중 남자는 4 명이었다. 1년, 2년의 무진행 생존률은 각각 76.9와 53.8%였다. 단병량 분석은 성별과 잔존 암여부(p = 0.0475 and p = 0.0475, 각각)에 따라 무진행 생존률이 진행한 그룹과 진행하지 않은 그룹 사이에 유의한 차이가 있다는 것을 보여줬다. 결론 : 외부 방사선 치료 전에 잔존 암이 없었던 환자의 100%에서 국소 및 부위 재발이 일어나지 않았다. 외부방사선 치료는 수술과 방사선요오드 치료에 반응하지 않는 환자 중 수술 후 잔존 암이 없는 경우에 효과적인 치료 방법이 될 수 있다.

• The korean journal of orthodontics
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• v.29 no.4 s.75
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• pp.457-466
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• 1999

It has been reported that skeletal relapse and dental change after mandibular setback do occur not only after intermaxillary fixation(IMF) removal but also during IMF The side effects of skeletal relapse during IMF have clinical importance because they can cause many Postoperative orthodontic Problems. Generally, the Prevention of solid union between segments, compensatory tooth movement, anterior openbite, etc. have been cited as the side effects of jaw displacement. The purpose of this study was to evaluate the skeletal relapse and dental change during IMF. The material consisted of 28 patients who were treated by BSSRO(bilateral sagittal split ramus osteotomy), wire osteosynthesis, IMF for correction of mandibular prognathism. Through cephalometric analysis, the amount and direction of surgical movement, skeletal relapse and dental change during IMF were measured. The correlation between surgical movement and skeletal relapse, between skeletal relapse and dental changes were evaluated. The following conclusions were obtained; 1. Distal segment was repositioned backward and upward, proximal segment showed clockwise rotation during surgery. 2. During ]m, anterior portion of distal segment was displaced backward and posterior portion was displaced upward. Proximal segment was displaced upward with forward movement of p-Go(gonion of proximal segment). Backward surgical movement of p-GO was significantly correlated with forward displacement of p-Go. 3. Overjet and overbite were not changed during IMF. The compensatory tooth movements during IMF were characterized by retroclination of upper incisors md retroclination, extrusion of lower incisors. These compensatory tooth movements had statistically significant correlation with upward displacement of d-Go (gonion of distal segment).