• The Korean Journal of Pain
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• 제34권2호
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• pp.229-233
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• 2021

Background: Iliotibial band friction syndrome (ITBFS) is a common disorder of the lateral knee. Previous research has reported that the iliotibial band (ITB) thickness (ITBT) is correlated with ITBFS, and ITBT has been considered to be a key morphologic parameter of ITBFS. However, the thickness is different from inflammatory hypertrophy. Thus, we made the ITB cross-sectional area (ITBCSA) a new morphological parameter to assess ITBFS. Methods: Forty-three patients with ITBFS group and from 43 normal group who underwent T1W magnetic resonance imaging were enrolled. The ITBCSA was measured as the cross-sectional area of the ITB that was most hypertrophied in the magnetic resonance axial images. The ITBT was measured as the thickest site of ITB. Results: The mean ITBCSA was 25.24 ± 6.59 ㎟ in the normal group and 38.75 ± 9.11 ㎟ in the ITBFS group. The mean ITBT was 1.94 ± 0.41 mm in the normal group and 2.62 ± 0.46 mm in the ITBFS group. Patients in ITBFS group had significantly higher ITBCSA (P < 0.001) and ITBT (P < 0.001) than the normal group. A receiver operator characteristic curve analysis demonstrated that the best cut-off value of the ITBT was 2.29 mm, with 76.7% sensitivity, 79.1% specificity, and area under the curve (AUC) 0.88. The optimal cut-off score of the ITBCSA was 30.66 ㎟, with 79.1% sensitivity, 79.1% specificity, and AUC 0.87. Conclusions: ITBCSA is a new and sensitive morphological parameter for diagnosing ITBFS, and may even be more accurate than ITBT.

• 대한원격탐사학회지
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• 제36권6_1호
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• pp.1367-1377
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• 2020

본 연구는 2016년 발생한 9.12 경주지진을 중심으로 경주시 건축물의 지진 취약성을 평가하고 지도를 제작하는데 목적이 있다. 지진 취약성을 평가하기위해 지질공학, 물리, 구조적 요인과 관련된 11개의 영향인자를 선정하였으며, 이는 독립변수로 적용되었다. 종속변수로는 9.12 경주지진 당시 실제 피해 입은 건축물의 위치자료가 사용되었다. 평가 모델은 기계학습 방법의 RF와 SVM을 기반으로 구축하였으며, 훈련 및 검증 데이터셋은 70:30 비율로 무작위 선별되었다. 정확도 검증은 ROC 곡선을 사용하여 최적 모델을 선별하였으며, 각 모델의 정확도는 RF(1.000), SVM(0.998), 예측 정확도는 RF(0.947), SVM(0.926) 로 나타났다. RF 모델을 기반으로 경주시 전체 건축물의 예측 값을 도출하였으며, 이를 등급화 하여 지진 취약성 지도를 작성하였다. 행정동별 건물 등급 분포를 살펴본 결과, 황남동, 월성동, 선도동, 내남면이 취약성이 높은 지역으로, 양북면, 강동면, 양남면, 감포읍이 상대적으로 안전한 지역으로 나타났다.

• 한국정보통신학회논문지
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• 제25권5호
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• pp.719-730
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• 2021

본 논문에서는 산화아연/탄소 테이프/산화아연의 대칭 구조를 갖는 ZCZ-NG라는 샌드위치형 산화아연(ZnO) 압전 에너지 하베스팅 소자를 제시한다. 고품질의 ZCZ-NG 소자를 제작하기 위해 전도성 양면 접착 탄소 테이프를 활용하였으며, 이는 매우 높은 피크 투 피크 전압(V_pp)을 발생시키는 ZCZ-NG 소자의 개발로 이어졌다. ZCZ-NG 소자의 크기, 산화아연 층의 두께 그리고 벤딩 변형률 변화에 따른 ZCZ-NG 소자의 출력 성능 변화를 측정, 분석하였다. 또한 제작된 ZCZ-NG 소자의 실효성 및 응용 가능성을 검증하기 위한 실험적인 센서 네트워크 테스트베드를 구축하였다. 상용 아두이노를 기반으로 한 송신, 수신 노드들로 이루어진 테스트베드에서 노드들은 각 노드에서 감지한 정보들을 무선으로 송수신한다. 본 연구에서 사용된 대칭 구조의 샌드위치형 ZCZ-NG 소자 제작 기술과 센서 네트워크와의 융합 연구가 앞으로 더 발전되어 사물인터넷 구현을 위한 자가발전 센서 네트워크 연구에 도움이 되길 바란다.

• 대한치과교정학회지
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• 제52권1호
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• pp.3-19
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• 2022

Objective: The purpose of this study was to investigate the accuracy of one-step automated orthodontic diagnosis of skeletodental discrepancies using a convolutional neural network (CNN) and lateral cephalogram images with different qualities from nationwide multi-hospitals. Methods: Among 2,174 lateral cephalograms, 1,993 cephalograms from two hospitals were used for training and internal test sets and 181 cephalograms from eight other hospitals were used for an external test set. They were divided into three classification groups according to anteroposterior skeletal discrepancies (Class I, II, and III), vertical skeletal discrepancies (normodivergent, hypodivergent, and hyperdivergent patterns), and vertical dental discrepancies (normal overbite, deep bite, and open bite) as a gold standard. Pre-trained DenseNet-169 was used as a CNN classifier model. Diagnostic performance was evaluated by receiver operating characteristic (ROC) analysis, t-stochastic neighbor embedding (t-SNE), and gradient-weighted class activation mapping (Grad-CAM). Results: In the ROC analysis, the mean area under the curve and the mean accuracy of all classifications were high with both internal and external test sets (all, > 0.89 and > 0.80). In the t-SNE analysis, our model succeeded in creating good separation between three classification groups. Grad-CAM figures showed differences in the location and size of the focus areas between three classification groups in each diagnosis. Conclusions: Since the accuracy of our model was validated with both internal and external test sets, it shows the possible usefulness of a one-step automated orthodontic diagnosis tool using a CNN model. However, it still needs technical improvement in terms of classifying vertical dental discrepancies.

• Journal of Chest Surgery
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• 제55권2호
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• pp.143-150
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• 2022

Background: The effectiveness of extracorporeal membrane oxygenation (ECMO) for patients with refractory cardiogenic shock or cardiac arrest is being established, and serum lactate is well known as a biomarker of end-organ perfusion. We evaluated the efficacy of pre-ECMO lactate for predicting 6-month survival in patients with acute coronary syndrome (ACS) undergoing ECMO. Methods: We reviewed the medical records of 148 patients who underwent veno-arterial (VA) ECMO for ACS between January 2015 and June 2020. These patients were divided into survivors and non-survivors based on 6-month survival. All clinical data before and during ECMO were compared between the 2 groups. Results: Patients' mean age was 66.0±10.5 years, and 116 (78.4%) were men. The total survival rate was 45.9% (n=68). Cox regression analysis showed that the pre-ECMO lactate level was an independent predictor of 6-month mortality (hazard ratio, 1.210; 95% confidence interval [CI], 1.064-1.376; p=0.004). The area under the receiver operating characteristic curve of pre-ECMO lactate was 0.64 (95% CI, 0.56-0.72; p=0.002; cut-off value=9.8 mmol/L). Kaplan-Meier survival analysis showed that the cumulative survival rate at 6 months was significantly higher among patients with a pre-ECMO lactate level of 9.8 mmol/L or less than among those with a level exceeding 9.8 mmol/L (57.3% vs. 31.8%, p=0.0008). Conclusion: A pre-ECMO lactate of 9.8 mmol/L or less may predict a favorable outcome at 6 months in ACS patients undergoing VA-ECMO. Further research aiming to improve the accuracy of predictions of reversibility in patients with high pre-ECMO lactate levels is essential.

• Nutrition Research and Practice
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• 제16권5호
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• pp.604-615
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• 2022

BACKGROUND/OBJECTIVES: This study aimed to investigate cancer-specific survival (CSS) and associated risk factors in elderly gastric cancer (EGC) patients. SUBJECTS/METHODS: EGC patients (≥ 70 yrs) who underwent curative gastrectomy between January 2013 and December 2017 at our hospital were included. Clinicopathologic characteristics and survival data were collected. Receiver operating characteristic (ROC) analysis was used to extract the best cutoff point for body mass index (BMI). A Cox proportional hazards model was used to determine the risk factors for CSS. RESULTS: In total, 290 EGC patients were included, with a median age of 74.7 yrs. The median follow-up time was 31 (1-77) mon. The postoperative 1-yr, 3-yr and 5-yr CSS rates were 93.7%, 75.9% and 65.1%, respectively. Univariate analysis revealed risk factors for CSS, including age (hazard ratio [HR] = 1.08; 95% confidence interval [CI], 1.01-1.15), intensive care unit (ICU) admission (HR = 1.73; 95% CI, 1.08-2.79), nutritional risk screening (NRS 2002) score ≥ 5 (HR = 2.33; 95% CI, 1.49-3.75), and preoperative prognostic nutrition index score < 45 (HR = 2.06; 95% CI, 1.27-3.33). The ROC curve showed that the best BMI cutoff value was 20.6 kg/m². Multivariate analysis indicated that a BMI ≤ 20.6 kg/m² (HR = 2.30; 95% CI, 1.36-3.87), ICU admission (HR = 1.97; 95% CI, 1.17-3.30) and TNM stage (stage II: HR = 5.56; 95% CI, 1.59-19.43; stage III: HR = 16.20; 95% CI, 4.99-52.59) were significantly associated with CSS. CONCLUSIONS: Low BMI (≤ 20.6 kg/m²), ICU admission and advanced pathological TNM stages (II and III) are independent risk factors for CSS in EGC patients after curative gastrectomy. Nutrition support, better perioperative management and early diagnosis would be helpful for better survival.

• The Korean Journal of Pain
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• 제36권1호
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• pp.113-127
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• 2023

Background: Resting-state functional connectivity (rs-FC) may aid in understanding the link between painmodulating brain regions and the descending pain modulatory system (DPMS) in fibromyalgia (FM). This study investigated whether the differences in rs-FC of the primary somatosensory cortex in responders and non-responders to the conditioned pain modulation test (CPM-test) are related to pain, sleep quality, central sensitization, and the impact of FM on quality of life. Methods: This cross-sectional study included 33 females with FM. rs-FC was assessed by functional magnetic resonance imaging. Change in the numerical pain scale during the CPM-test assessed the DPMS function. Subjects were classified either as non-responders (i.e., DPMS dysfunction, n = 13) or responders (n = 20) to CPM-test. A generalized linear model (GLM) and a receiver operating characteristic (ROC) curve analysis were performed to check the accuracy of the rs-FC to differentiate each group. Results: Non-responders showed a decreased rs-FC between the left somatosensory cortex (S1) and the periaqueductal gray (PAG) (P < 0.001). The GLM analysis revealed that the S1-PAG rs-FC in the left-brain hemisphere was positively correlated with a central sensitization symptom and negatively correlated with sleep quality and pain scores. ROC curve analysis showed that left S1-PAG rs-FC offers a sensitivity and specificity of 85% or higher (area under the curve, 0.78, 95% confidence interval, 0.63-0.94) to discriminate who does/does not respond to the CPM-test. Conclusions: These results support using the rs-FC patterns in the left S1-PAG as a marker for predicting CPM-test response, which may aid in treatment individualization in FM patients.

• 지식경영연구
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• 제23권4호
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• pp.275-294
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• 2022

최근 몇 년 동안 전자상거래와 소셜미디어의 지속적인 통합 발전과 함께 소셜커머스는 신뢰 중심의 사회적 거래 방식으로서 전자상거래의 중요한 형태로 자리를 잡았다. 온라인 커뮤니티의 긍정적인 측면과 풍부한 사용자 제작 콘텐츠 (UGC)로 인해 커뮤니티에 참여하는 사용자와 기업이 점점 더 증가하고 있는 추세이다. 이러한 상황에서 정보접근 비용은 지속적으로 감소하고 있고 구매 프로세스는 보다 간결하고 효율적으로 개선되고 있는 반면에 소비자의 충동구매 가능성을 크게 높이는 결과를 가져오게 된다. 그럼에도 불구하고 아직까지 소셜커머스에서 UGC의 특성을 기반으로 한 소비자 충동구매의 메커니즘에 대한 실증적 연구는 거의 없다. 본 연구는 자극-유기체-반응 (S-O-R) 모델을 이용하여 소셜커머스에서 UGC 특성이 소비자 충동구매에 미치는 영향을 분석하는 연구모형을 구축하였고, 이 과정에서 지각된 위험을 매개변수로, 유대강도를 조절변수로 각각 설정하였다. 실증분석 결과 콘텐츠 진정성, 콘텐츠 유용성, 그리고 콘텐츠 가치는 구매의사결정 과정에서 소비자의 지각된 위험에 유의한 영향을 미치고, 소비자의 지각된 위험은 충동구매에 유의한 영향을 미치는 것으로 나타났다. 한편, UGC 생산자와 이용자 간의 유대강도는 콘텐츠 유용성과 지각된 위험의 관계 및 지각된 위험과 충동구매 관계를 조절하는 것으로 나타났다. 이러한 연구결과는 소셜커머스 사업자들로 하여금 고객의 소비행동에 대한 심층적인 이해를 도울 뿐만 아니라 소비자 충동구매가 왜 일어나는지에 대한 메커니즘을 학술적 관점에서 분석할 수 있는 이론적 틀을 제공하였다는 점에서 의의가 있다.

• 한국지형학회지
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• 제27권1호
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• pp.61-89
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• 2020

The objective of this study is to characterize landslide susceptibility depending on various geo-environmental variables as well as to compare the Frequency Ratio (FR) and Evidential Belief Function (EBF) methods for landslide susceptibility analysis of rainfall-induced landslides. In 2013, a total of 259 landslides occurred in Chuncheon, Gangwon Province, South Korea, due to heavy rainfall events with a total cumulative rainfall of 296~721mm in 106~231 hours duration. Landslides data were mapped with better accuracy using the geographic information system (ArcGIS 10.6 version) based on the historic landslide records in Chuncheon from the National Disaster Management System (NDMS), the 2013 landslide investigation report, orthographic images, and aerial photographs. Then the landslides were randomly split into a testing dataset (70%; 181 landslides) and validation dataset (30%; 78 landslides). First, geo-environmental variables were analyzed by using FR and EBF functions for the full data. The most significant factors related to landslides were altitude (100~200m), slope (15~25°), concave plan curvature, high SPI, young timber age, loose timber density, small timber diameter, artificial forests, coniferous forests, soil depth (50~100cm), very well-drained area, sandy loam soil and so on. Second, the landslide susceptibility index was calculated by using selected geo-environmental variables. The model fit and prediction performance were evaluated using the Receiver Operating Characteristic (ROC) curve and the Area Under Curve (AUC) methods. The AUC values of both model fit and prediction performance were 80.5% and 76.3% for FR and 76.6% and 74.9% for EBF respectively. However, the landslide susceptibility index, with classes of 'very high' and 'high', was detected by 73.1% of landslides in the EBF model rather than the FR model (66.7%). Therefore, the EBF can be a promising method for spatial prediction of landslide occurrence, while the FR is still a powerful method for the landslide susceptibility mapping.

• Korean Journal of Radiology
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• 제25권2호
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• pp.189-198
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• 2024

Objective: To investigate the prognostic utility of radiomics features extracted from ¹⁸F-fluorodeoxyglucose (FDG) PET/CT combined with clinical factors and metabolic parameters in predicting progression-free survival (PFS) and overall survival (OS) in individuals diagnosed with extranodal nasal-type NK/T cell lymphoma (ENKTCL). Materials and Methods: A total of 126 adults with ENKTCL who underwent ¹⁸F-FDG PET/CT examination before treatment were retrospectively included and randomly divided into training (n = 88) and validation cohorts (n = 38) at a ratio of 7:3. Least absolute shrinkage and selection operation Cox regression analysis was used to select the best radiomics features and calculate each patient's radiomics scores (RadPFS and RadOS). Kaplan-Meier curve and Log-rank test were used to compare survival between patient groups risk-stratified by the radiomics scores. Various models to predict PFS and OS were constructed, including clinical, metabolic, clinical + metabolic, and clinical + metabolic + radiomics models. The discriminative ability of each model was evaluated using Harrell's C index. The performance of each model in predicting PFS and OS for 1-, 3-, and 5-years was evaluated using the time-dependent receiver operating characteristic (ROC) curve. Results: Kaplan-Meier curve analysis demonstrated that the radiomics scores effectively identified high- and low-risk patients (all P < 0.05). Multivariable Cox analysis showed that the Ann Arbor stage, maximum standardized uptake value (SUVmax), and RadPFS were independent risk factors associated with PFS. Further, β2-microglobulin, Eastern Cooperative Oncology Group performance status score, SUVmax, and RadOS were independent risk factors for OS. The clinical + metabolic + radiomics model exhibited the greatest discriminative ability for both PFS (Harrell's C-index: 0.805 in the validation cohort) and OS (Harrell's C-index: 0.833 in the validation cohort). The time-dependent ROC analysis indicated that the clinical + metabolic + radiomics model had the best predictive performance. Conclusion: The PET/CT-based clinical + metabolic + radiomics model can enhance prognostication among patients with ENKTCL and may be a non-invasive and efficient risk stratification tool for clinical practice.