• Journal of Korean Neurosurgical Society
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• 제59권6호
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• pp.622-627
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• 2016

Objective : Although a high incidence of chronic subdural hematoma (CSDH) following traumatic subdural hygroma (SDG) has been reported, no study has evaluated risk factors for the development of CSDH. Therefore, we analyzed the risk factors contributing to formation of CSDH in patients with traumatic SDG. Methods : We retrospectively reviewed patients admitted to Hallym University Hospital with traumatic head injury from January 2004 through December 2013. A total of 45 patients with these injuries in which traumatic SDG developed during the follow-up period were analyzed. All patients were divided into two groups based on the development of CSDH, and the associations between the development of CSDH and independent variables were investigated. Results : Thirty-one patients suffered from bilateral SDG, whereas 14 had unilateral SDG. Follow-up computed tomography scans revealed regression of SDG in 25 of 45 patients (55.6%), but the remaining 20 patients (44.4%) suffered from transition to CSDH. Eight patients developed bilateral CSDH, and 12 patients developed unilateral CSDH. Hemorrhage-free survival rates were significantly lower in the male and bilateral SDG group (logrank test; p=0.043 and p=0.013, respectively). Binary logistic regression analysis revealed male (OR, 7.68; 95% CI 1.18-49.78; p=0.033) and bilateral SDG (OR, 8.04; 95% CI 1.41-45.7; p=0.019) were significant risk factors for development of CSDH. Conclusion : The potential to evolve into CSDH should be considered in patients with traumatic SDG, particularly male patients with bilateral SDG.

• 지능정보연구
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• 제11권3호
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• pp.69-81
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• 2005

고객관계관리는 치열한 경쟁환경에서 각 기업이 생존하기 위해 반드시 필요한 하나의 기업전략이 되었다. 고객관계관리의 방법은 다양하지만 가장 기본적인 방법은 특정 고객이 어떤 상품 혹은 상품군을 구매할 것인지를 정확히 예측하는 것이다. 이미 국내외 실무현장에서 전통적인 데이터마이닝 기법을 활용한 고객구매예측모형이 널리 적용되고 있다. 하지만 전통적인 기법의 경우, 정확도가 상대적으로 떨어지거나 혹은 모형의 구축 및 유지관리가 어렵다는 문제가 종종 제기되어 왔다. 이에 본 연구에서는 기존 모형의 문제점을 개선하기 위한 대안으로, 매우 높은 예측력을 나타내면서 동시에 일반화 능력이 우수한 것으로 알려진 Support Vector Machine(SVM)을 이용하여 고객구매예측모형을 구축하고자 한다. 본 연구에서는 고객구매예측의 도구로써 SVM의 적합성을 판단하기 위하여 전통적인 기법인 로지스틱 회귀분석, 인공신경망과 그 성과를 비교하였다. 그 결과, SVM이 다른 기법들에 비해 상대적으로 우수한 성과를 나타냄을 확인할 수 있었다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권5호
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• pp.2225-2229
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• 2014

Background: Carcinoma of the tongue is the most common intra-oral malignancy in Western countries. Incidence and mortality rates have increased in recent years, and survival has not improved. This study aimed to determine etiologic factors for tongue cancer with age-sex matched case-control data. Materials and Methods: 47 patients with carcinoma of the tongue referred to our oral medicine clinic between years 2005-2006 were analyzed and compared with control group data. The medical records, including family history of cancer, dental trauma, and history of abuse of alcohol and tobacco products was recorded for all subjects. Chi square comparison tests and linear regression analysis were performed using the SPSS program for statistics. Results: Patient and randomly selected control groups each consisted of 30 male and 17 female subjects with mean ages 53.2 (${\pm}12.6$) and 52.6 (${\pm}11.5$) years respectively. Smoking and alcohol abuse proportions were significantly higher in the patient group (p=0.0001, p<0.0001 respectively). Chronic mechanical trauma was observed in 44.7% of the patients and 17.0% of the control group (p=0.004). Similarly, family history of cancer of any type (for the first degree relatives) was found to be more common in the patient group (p=0.009). On regression analysis, alcohol abuse, family history of cancer, smoking, chronic mechanical traumas appeared as significant etiologic factors (p=0.0001). Conclusions: We believe that field cancerization may become evident in oral and oropharyngeal mucosa with multiple steps of molecular changes starting from the first sign of dysplasia with chronic exposure to etiological factors. Chronic trauma cases need particular attention to search for very early signs of cancer.

• Asian Pacific Journal of Cancer Prevention
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• 제16권4호
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• pp.1627-1631
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• 2015

Background: Stage at diagnosis is one of the most important prognostic factors of breast cancer survival. Because in the breast cancer case this may vary with socioeconomic characteristics, this study was performed to recognize the relationship between demographic and socioeconomic factors with stage at diagnosis in Iran. Materials and Methods: This cross-sectional, descriptive study conducted on 526 patients suffering from breast cancer and registered in Cancer Research Center of Shahid Beheshti University of Medical Sciences from 2008 to 2013. A reliable and valid questionnaire about family levels of socioeconomic status filled in by interviewing the patients via phone. For analyzing the data, Multinomial logistic regression, Kendal tau-b correlation coefficient and Contingency Coefficient tests were executed by SPSS22. Economic status, educational attainment of patient and household head and/or a combination of these were considered as parameters for socioeconomic status. First, the relationship between stage at diagnosis and demographic and socioeconomic status was assessed in univariate analysis then these relationships assessed in two different models of multinomial logistic regression. Results: The mean age of the patients was 48.3 (SD=11.4). According to the results of this study, there were significant relationships between stage at diagnosis of breast cancer with patient education (p=0.011), living place (p=0.044) and combined socioeconomic status (p=0.024). These relationships persisted in multiple multinomial logistic regressions. Other variables, however, had no significant correlation. Conclusions: Patient education, combined socioeconomic status and living place are important variables in stage at diagnosis of breast cancer in Iranian women. Interventions have to be applied with the aim of raising women's accessibility to diagnostic and medical facilities and also awareness in order to reducing delay in referring. In addition, covering breast cancer screening services by insurance is recommended.

• Asian Pacific Journal of Cancer Prevention
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• 제16권4호
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• pp.1355-1360
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• 2015

Background: The number of cancer survivors is increasing globally and recently, higher rates of comorbidities in cancer survivors have been reported. However, no studies have investigated whether cancer survivors have a higher risk of chronic kidney disease (CKD). Accordingly, our study evaluated the association between cancer survivors and the risk of CKD using the 2010-2012 Korean National Health and Nutrition Examination Survey. Materials and Methods: A total of 11,407 participants aged 40 years and over were categorized into two groups according to cancer experience. Multiple variables were compared and the odds ratios (ORs) for CKD prevalence were calculated using a weighted logistic regression analysis between the two groups. Results: Cancer survivors were older than were those in the non-cancer group, on average, the percentages of glomerular filtration rate(GFR) lower than $60mL/min/1.73m^2$, proteinuria, and CKD were significantly higher in cancer survivors when compared to controls. Weighted logistic regression analyses demonstrated that cancer survivors had a higher risk for CKD after adjusting for multiple variables (OR (95% confidence interval), 2.88 (1.48-5.59)). Conclusions: Our study demonstrated a possible association between CKD and cancer survival in Korean adults. Identifying and correcting risk factors for cancer survivors would positively affect prevention of CKD and result in a better cancer prognosis.

• 기술혁신연구
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• 제18권1호
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• pp.21-51
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• 2010

본 연구는 한국 벤처부문의 지식이전 효과를 실증적으로 분석했다. 구체적으로, 지식을 창출하는 단계에서부터 어떤 지식창조기관(주로 대학 출연연구소 기업R&D센터)에서 어떤 유형의 지식이 공급되는지 또한 그 성과는 어떠한지를 규명했다. 종속변수의 유형에 따라 3가지 분석방법인, ‘위계회귀분석’, ‘로지스틱 회귀분석’ 및 ‘생존분석’을 사용했다. 분석 대상은 벤처인증기업 중 1,862개를 분석했으며, 데이터의 원천은 2008년도 STEPI 혁신조사를 비롯해서 정부부처에서 공표되는 객관적 데이터들을 사용했다. 주요 분석결과는 지식원천과 산업유형이 정렬될수록 그 지식이전은 특허를 높이고 성장성을 높였으며, 정부지원은 재무성과에 부정적 영향을 미쳤으나 지식이전에 대한 영향은 없었다. 또한 각 벤처기업의 흡수능력에 따라 지식이전 효과가 차별화되었다. 한국 벤처부문에서 발생하는 정부와 벤처캐피탈 시장의 역할에 대한 이론적 및 실무적 시사점을 토론했다.

• Journal of the Korean Data and Information Science Society
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• 제23권4호
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• pp.739-748
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• 2012

최소제곱 서포트벡터기계 (least squares support vector machine)는 분류 및 비선형 회귀분석에서 유용하게 사용되고 있는 통계적 기법이다. 본 논문에서는 각 집단별로 생존자료가 관측된 경우 적용할 수 있는 LS-SVM을 제안한다. 제안된 모형은 임의우측 중도절단자료를 비선형 회귀모형에 적용할 수 있게 Kaplan- Meier의 중도절단분포의 추정값을 이용하여 구해진 가중값을 사용하고, 집단 간의 변동을 나타내기 위하여 임의효과항을 포함한다. 벌칙상수와 커널모수의 최적값을 구하기 위하여 일반화 교차타당성함수가 사용되고 모의실험에서는 임의효과항을 포함하지 않은 LS-SVM과 성능을 비교함으로써 제안된 방법의 우수성을 보이기로 한다.

• Journal of Periodontal and Implant Science
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• 제49권5호
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• pp.287-298
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• 2019

Purpose: The aim of this retrospective study was to determine the prevalence of early implant failure using a single implant system and to identify the factors contributing to early implant failure. Methods: Patients who received implant treatment with a single implant system ($Luna^{(R)}$, Shinhung, Seoul, Korea) at Dankook University Dental Hospital from 2015 to 2017 were enrolled. The following data were collected for analysis: sex and age of the patient, seniority of the surgeon, diameter and length of the implant, position in the dental arch, access approach for sinus-floor elevation, and type of guided bone regeneration (GBR) procedure. The effect of each predictor was evaluated using the crude hazard ratio and the adjusted hazard ratio (aHR) in univariate and multivariate Cox regression analyses, respectively. Results: This study analyzed 1,031 implants in 409 patients, who comprised 169 females and 240 males with a median age of 54 years (interquartile range [IQR], 47-61 years) and were followed up for a median of 7.2 months (IQR, 5.6-9.9 months) after implant placement. Thirty-five implants were removed prior to final prosthesis delivery, and the cumulative survival rate in the early phase at the implant level was 95.6%. Multivariate regression analysis revealed that seniority of the surgeon (residents: aHR=2.86; 95% confidence interval [CI], 1.37-5.94) and the jaw in which the implant was placed (mandible: aHR=2.31; 95% CI, 1.12-4.76) exerted statistically significant effects on early implant failure after adjusting for sex, age, dimensions of the implant, and type of GBR procedure (preoperative and/or simultaneous) (P<0.05). Conclusions: Prospective studies are warranted to further elucidate the factors contributing to early implant failure. In the meantime, surgeons should receive appropriate training and carefully select the bone bed in order to minimize the risk of early implant failure.

• Investigative and Clinical Urology
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• 제59권6호
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• pp.376-382
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• 2018

Purpose: The authors performed this study to investigate the risk factors for predicting stent failure and to evaluate its impact on prognosis. Materials and Methods: Between January 2002 and March 2017, we retrospectively reviewed 117 consecutive patients who underwent retrograde ureteral stenting and exchanging at least once every 3 months for malignant ureteral obstruction. The patients were classified according to their pre-stenting chronic kidney disease (CKD) stage. The factors affecting stent failure were analyzed using a logistic regression model. Overall survival (OS) was estimated, and the prognostic significance of each variable was estimated using Cox proportional-hazards regression modeling. Results: Before stenting, 91 patients were CKD stages 1-3 and 26 patients were CKD stages 4-5. These two groups differed significantly only in pre-stenting estimated glomerular filtration rate (eGFR), bilateral obstruction, and pre-stenting pyuria. Among the 117 patients, stent failure occurred in 30 patients (25.6%), and there were no differences between the groups. Pre-stenting pyuria and post-stenting complications were significant predictors of stent failure. There were 79 deaths in total, including 56 in the CKD stages 1-3 group and 23 in the CKD stages 4-5 group. In the multivariate analysis predicting patient OS, pre-stenting eGFR and post-stenting disease progression were significant factors. Conclusions: Internal ureteral stenting was effective for maintaining renal function in malignant ureteral obstruction. However, it did not restore renal function, which is related to the prognosis of the patients. Therefore, to improve patients' renal function and prognosis, patients who require stenting must be quickly recognized and treated.

• 한국수산과학회지
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• 제56권6호
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• pp.870-877
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• 2023

The purpose of this study was to assess the efficiency of nitrification based on ammonia loading rates and hydraulic air-loading rates in a moving bed bioreactor (MBBR) under seawater conditions. The goal was to provide foundational data for the design of these bio reactors. At an ammonia loading rate of 0.2 g TAN·m^-2 surface area·day^-1, the influent TAN concentration was determined to be 1.76±0.33 mg·L^-1, which is below the safe concentration for fish survival (2 mg·L^-1). Considering operational aspects, the optimal ammonia-loading rate was derived. Subsequently, experimental results for nitrification efficiency at the optimal ammonia-loading rate revealed that the optimum hydraulic air-loading rate was 1.8 L·air·m^-2 surface area·min^-1. This condition resulted in the lowest concentrations of TAN and NO₂-N in the influent water, thus establishing the optimal hydraulic air-loading rate. A regression equation was derived for the ammonia-removal rate (Y) based on the ammonia-loading rate (x) and expressed as a 0.5-order equation (Y=ax^0.5+b). Specifically, for TAN concentrations of 0-6 mg·L-1, the regression equation Y=0.1683x^0.5-0.13628, was established.