• 한국전자통신학회논문지
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• 제19권1호
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• pp.65-76
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• 2024

최근 해상풍력산업이 활성화되면서 기존 화력 발전소 규모의 400MW 급 발전단지들이 개발되고 있다. 재생에너지는 에너지원에 따라 간헐성이 큰 특성이 있고, 최신 재생에너지 발전설비들은 제어기능을 갖는 인버터 기술로 구성되는 특징이 있다. 이러한 재생에너지원의 계통연계 확대에 따라 전력계통 접속을 위한 그리드코드도 점점 구체화되고 있고, 이에 따라 관련 검토도 활발히 진행되고 있다. 본 논문에서는 그리드 코드 준수를 위해 여러 해상풍력 발전단지들을 통합하여 공동접속설비로 접속하는 경우, 최적 무효전력 보상용량 선정 방법에 대해 제안한다. 그리드 코드의 요구조건을 기반으로, 전북 서남해 400MW 풍력발전단지의 무효전력 보상과 과도안정도를 분석한다. 이 분석은 PSS/E를 사용하여 각 터빈 배치안과 케이블 데이터로 발전단지 DB를 구축하고, 내·외부망 케이블의 충전전류에 의한 무효전력과 연계점에서 무효전력 보상용량을 산출한다. 또한 전력계통 DB에 연계해서 정적, 동적 안정도를 고찰한다.

• Korean Journal of Radiology
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• 제24권4호
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• pp.294-304
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• 2023

Objective: We aimed to investigate whether image standardization using deep learning-based computed tomography (CT) image conversion would improve the performance of deep learning-based automated hepatic segmentation across various reconstruction methods. Materials and Methods: We collected contrast-enhanced dual-energy CT of the abdomen that was obtained using various reconstruction methods, including filtered back projection, iterative reconstruction, optimum contrast, and monoenergetic images with 40, 60, and 80 keV. A deep learning based image conversion algorithm was developed to standardize the CT images using 142 CT examinations (128 for training and 14 for tuning). A separate set of 43 CT examinations from 42 patients (mean age, 10.1 years) was used as the test data. A commercial software program (MEDIP PRO v2.0.0.0, MEDICALIP Co. Ltd.) based on 2D U-NET was used to create liver segmentation masks with liver volume. The original 80 keV images were used as the ground truth. We used the paired t-test to compare the segmentation performance in the Dice similarity coefficient (DSC) and difference ratio of the liver volume relative to the ground truth volume before and after image standardization. The concordance correlation coefficient (CCC) was used to assess the agreement between the segmented liver volume and ground-truth volume. Results: The original CT images showed variable and poor segmentation performances. The standardized images achieved significantly higher DSCs for liver segmentation than the original images (DSC [original, 5.40%-91.27%] vs. [standardized, 93.16%-96.74%], all P < 0.001). The difference ratio of liver volume also decreased significantly after image conversion (original, 9.84%-91.37% vs. standardized, 1.99%-4.41%). In all protocols, CCCs improved after image conversion (original, -0.006-0.964 vs. standardized, 0.990-0.998). Conclusion: Deep learning-based CT image standardization can improve the performance of automated hepatic segmentation using CT images reconstructed using various methods. Deep learning-based CT image conversion may have the potential to improve the generalizability of the segmentation network.

• Korean Journal of Radiology
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• 제23권10호
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• pp.949-958
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• 2022

Objective: To investigate the feasibility of using a deep learning-based analysis of auscultation data to predict significant stenosis of arteriovenous fistulas (AVF) in patients undergoing hemodialysis requiring percutaneous transluminal angioplasty (PTA). Materials and Methods: Forty patients (24 male and 16 female; median age, 62.5 years) with dysfunctional native AVF were prospectively recruited. Digital sounds from the AVF shunt were recorded using a wireless electronic stethoscope before (pre-PTA) and after PTA (post-PTA), and the audio files were subsequently converted to mel spectrograms, which were used to construct various deep convolutional neural network (DCNN) models (DenseNet201, EfficientNetB5, and ResNet50). The performance of these models for diagnosing ≥ 50% AVF stenosis was assessed and compared. The ground truth for the presence of ≥ 50% AVF stenosis was obtained using digital subtraction angiography. Gradient-weighted class activation mapping (Grad-CAM) was used to produce visual explanations for DCNN model decisions. Results: Eighty audio files were obtained from the 40 recruited patients and pooled for the study. Mel spectrograms of "pre-PTA" shunt sounds showed patterns corresponding to abnormal high-pitched bruits with systolic accentuation observed in patients with stenotic AVF. The ResNet50 and EfficientNetB5 models yielded an area under the receiver operating characteristic curve of 0.99 and 0.98, respectively, at optimized epochs for predicting ≥ 50% AVF stenosis. However, Grad-CAM heatmaps revealed that only ResNet50 highlighted areas relevant to AVF stenosis in the mel spectrogram. Conclusion: Mel spectrogram-based DCNN models, particularly ResNet50, successfully predicted the presence of significant AVF stenosis requiring PTA in this feasibility study and may potentially be used in AVF surveillance.

• 경영정보학연구
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• 제20권2호
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• pp.139-161
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• 2018

한국이 빠르게 고령화 사회에서 고령사회로 진입함에 따라 성공적인 노화, 노후 생활이 개인뿐만 아니라 사회적으로도 관심을 받고 있다. 이에 본 연구는 노인의 행복과 불행 관련된 신문 기사를 통해 전체적인 이해와 더불어 제안을 하기 위한 목적으로 연구를 진행했다. 노인의 행복과 불행에 관련된 기존 연구는 연구대상의 특성상 인터뷰 혹은 인터뷰를 동반한 설문조사의 방법론을 사용해 영향요인을 재확인하거나, 단일효과를 검증하는데 머물렀다. 또한 노인의 행복과 불행에 영향을 미치는 중요한 요인 파악과 더불어 정부, 기업, 가정 및 기타 사회 복지기관으로 분류하여 실증적인 행복 증진, 불행 경감 방안을 제시한 연구가 이루어지지 않았다. 따라서 본 연구는 Alderfer의 ERG 이론을 기반으로 검색어를 선정해 18년간(수집 기간: 2001. 08~2018. 02) 온라인 신문기사를 총 211,309건(행복: 200,246건, 불행: 11,063건)을 수집하여 연구를 진행했다. 분석결과 행복 관련 토픽은 연금, 사회 인프라, 건강, 공동체, 복지, 문화생활, 성공적인 노후, 봉사, 종교, 귀농으로 도출되었고, 불행 관련 토픽은 노인 우울, 복지 부족, 종교 의지, 질병, 은퇴 후 소득, 문화, 봉사, 역사적 사건, 예술, 가족 단절로 나타났다. 추가로 토픽 네트워크 분석을 통하여 각 토픽의 키워드 사이의 네트워크를 시각화했다. 따라서 본 연구는 결과를 통한 실현 가능한 제안을 했다는 점을 시사한다.

• IMMUNE NETWORK
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• 제21권4호
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• pp.25.1-25.16
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• 2021

Asthma is a heterogeneous disease whose development is shaped by a variety of environmental and genetic factors. While several recent studies suggest that microbial dysbiosis in the gut may promote asthma, little is known about the relationship between the recently discovered lung microbiome and asthma. Innate lymphoid cells (ILCs) have also been shown recently to participate in asthma. To investigate the relationship between the lung microbiome, ILCs, and asthma, we recruited 23 healthy controls (HC), 42 patients with non-severe asthma, and 32 patients with severe asthma. Flow cytometry analysis showed severe asthma associated with fewer natural cytotoxicity receptor (NCR)⁺ILC3s in the lung. Similar changes in other ILC subsets, macrophages, and monocytes were not observed. The asthma patients did not differ from the HC in terms of the alpha and beta-diversity of the lung and gut microbiomes. However, lung function correlated positively with both NCR⁺ILC3 frequencies and microbial diversity in the lung. Sputum NCR⁺ILC3 frequencies correlated positively with lung microbiome diversity in the HC, but this relationship was inversed in severe asthma. Together, these data suggest that airway NCR⁺ILC3s may contribute to a healthy commensal diversity and normal lung function.

• IMMUNE NETWORK
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• 제21권4호
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• pp.29.1-29.9
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• 2021

There are limited data directly comparing humoral and T cell responses to the ChAdOx1 nCoV-19 and BNT162b2 vaccines. We compared Ab and T cell responses after first doses of ChAdOx1 nCoV-19 vs. BNT162b2 vaccines. We enrolled healthcare workers who received ChAdOx1 nCoV-19 or BNT162b2 vaccine in Seoul, Korea. Anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) S1 protein-specific IgG Abs (S1-IgG), neutralizing Abs (NT Abs), and SARS-CoV-2-specific T cell response were evaluated before vaccination and at 1-wk intervals for 3 wks after vaccination. A total of 76 persons, comprising 40 injected with the ChAdOx1 vaccine and 36 injected with the BNT162b2 vaccine, participated in this study. At 3 wks after vaccination, the mean levels (±SD) of S1-IgG and NT Abs in the BNT162b2 participants were significantly higher than in the ChAdOx1 participants (S1-IgG, 14.03±7.20 vs. 6.28±8.87, p<0.0001; NT Ab, 183.1±155.6 vs. 116.6±116.2, p=0.035), respectively. However, the mean values of the T cell responses in the 2 groups were comparable after 2 wks. The humoral immune response after the 1st dose of BNT162b2 developed faster and was stronger than after the 1st dose of ChAdOx1. However, the T cell responses to BNT162b2 and ChAdOx1 were similar.

• IMMUNE NETWORK
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• 제22권2호
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• pp.17.1-17.14
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• 2022

We aimed to investigate associations of dietary diversity (DD) with gut microbial diversity and the development of hen's egg allergy (HEA) in infants. We enrolled 68 infants in a high-risk group and 32 infants in a control group based on a family history of allergic diseases. All infants were followed from birth until 12 months of age. We collected infant feeding data, and DD was defined using 3 measures: the World Health Organization definition of minimum DD, food group diversity, and food allergen diversity. Gut microbiome profiles and expression of cytokines were evaluated by bacterial 16S rRNA sequencing and real-time reverse transcriptase-polymerase chain reaction. High DD scores at 3 and 4 months were associated with a lower risk of developing HEA in the high-risk group, but not in the control group. In the high-risk group, high DD scores at 3, 4, and 5 months of age were associated with an increase in Chao1 index at 6 months. We found that the gene expression of IL-4, IL-5, IL-6, and IL-8 were higher among infants who had lower DD scores compared to those who had higher DD scores in high-risk infants. Additionally, high-risk infants with a higher FAD score at 5 months of age showed a reduced gene expression of IL-13. Increasing DD within 6 months of life may increase gut microbial diversity, and thus reduce the development of HEA in infants with a family history of allergic diseases.

• IMMUNE NETWORK
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• 제22권3호
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• pp.24.1-24.12
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• 2022

Coronavirus disease 2019 (COVID-19) vaccination in immunocompromised, especially transplant recipients, may induce a weaker immune response. But there are limited data on the immune response after COVID-19 vaccination in liver transplant (LT) recipients, especially on the comparison of Ab responses after different vaccine platforms between mRNA and adenoviral vector vaccines. Thus, we conducted a prospective study on LT recipients who received two doses of the ChAdOx1 nCoV-19 (ChAdOx1), mRNA-1273, or BNT162b2 vaccines compared with healthy healthcare workers (HCWs). SARS-CoV-2 S1-specific IgG Ab titers were measured using ELISA. Overall, 89 LT recipients (ChAdOx1, n=16 [18%]) or mRNA vaccines (mRNA-1273 vaccine, n=23 [26%]; BNT162b2 vaccine, n=50 [56%]) received 3 different vaccines. Of them, 16 (18%) had a positive Ab response after one dose of COVID-19 vaccine and 62 (73%) after 2 doses. However, the median Ab titer after two doses of mRNA vaccines was significantly higher (44.6 IU/ml) than after two doses of ChAdOx1 (19.2 IU/ml, p=0.04). The longer time interval from transplantation was significantly associated with high Ab titers after two doses of vaccine (p=0.003). However, mycophenolic acid use was not associated with Ab titers (p=0.53). In conclusion, about 3-quarters of LT recipients had a positive Ab response after 2 doses of vaccine, and the mRNA vaccines induced higher Ab responses than the ChAdOx1 vaccine.

• IMMUNE NETWORK
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• 제20권5호
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• pp.43.1-43.11
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• 2020

Capicua (CIC) is a transcriptional repressor that regulates several developmental processes. CIC deficiency results in lymphoproliferative autoimmunity accompanied by expansion of CD44^hiCD62L^lo effector/memory and follicular Th cell populations. Deletion of Cic alleles in hematopoietic stem cells (Vav1-Cre-mediated knockout of Cic) causes more severe autoimmunity than that caused by the knockout of Cic in CD4⁺CD8⁺ double positive thymocytes (Cd4-Cre-mediated knockout of Cic). In this study, we compared splenic CD4⁺ T cell activation and proliferation between whole immune cell-specific Cic-null (Cic^f/f;Vav1-Cre) and T cell-specific Cic-null (Cic^f/f;Cd4-Cre) mice. Hyperactivation and hyperproliferation of CD4⁺ T cells were more apparent in Cic^f/f;Vav1-Cre mice than in Cic^f/f;Cd4-Cre mice. Cic^f/f;Vav1-Cre CD4⁺ T cells more rapidly proliferated and secreted larger amounts of IL-2 upon TCR stimulation than did Cic^f/f;Cd4-Cre CD4⁺ T cells, while the TCR stimulation-induced activation of the TCR signaling cascade and calcium flux were comparable between them. Mixed wild-type and Cic^f/f;Vav1-Cre bone marrow chimeras also exhibited more apparent hyperactivation and hyperproliferation of Cic-deficient CD4⁺ T cells than did mixed wild-type and Cic^f/f;Cd4-Cre bone marrow chimeras. Taken together, our data demonstrate that CIC deficiency at the beginning of T cell development endows peripheral CD4⁺ T cells with enhanced T cell activation and proliferative capability.

• IMMUNE NETWORK
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• 제20권5호
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• pp.41.1-41.11
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• 2020

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) is a positive-sense single-stranded RNA (+ssRNA) that causes coronavirus disease 2019 (COVID-19). The viral genome encodes twelve genes for viral replication and infection. The third open reading frame is the spike (S) gene that encodes for the spike glycoprotein interacting with specific cell surface receptor - angiotensin converting enzyme 2 (ACE2) - on the host cell membrane. Most recent studies identified a single point mutation in S gene. A single point mutation in S gene leading to an amino acid substitution at codon 614 from an aspartic acid 614 into glycine (D614G) resulted in greater infectivity compared to the wild type SARS-CoV2. We were interested in investigating the mutation region of S gene of SARS-CoV2 from Korean COVID-19 patients. New mutation sites were found in the critical receptor binding domain (RBD) of S gene, which is adjacent to the aforementioned D614G mutation residue. This specific sequence data demonstrated the active progression of SARS-CoV2 by mutations in the RBD of S gene. The sequence information of new mutations is critical to the development of recombinant SARS-CoV2 spike antigens, which may be required to improve and advance the strategy against a wide range of possible SARS-CoV2 mutations.