• Geomechanics and Engineering
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• 제29권3호
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• pp.291-300
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• 2022

Tunnel boring machines combined with the earth pressure balanced shield method (EPB shield TBMs) have been adopted in urban areas as they allow excavation of tunnels with limited ground deformation through continuous and repetitive excavation and support. Nevertheless, the expansion of TBM construction requires much more minor and exquisitely controlled surface settlement to prevent economic loss. Several parametric studies controlling the tunnel's geometry, ground properties, and TBM operational factors assuming ordinary conditions for EPB shield TBM excavation have been conducted, but the impact of excessive excavation on the induced settlement has not been adequately studied. This study conducted a numerical evaluation of surface settlement induced by the ground loss from face imbalance, excessive excavation, and tail void grouting. The numerical model was constructed using FLAC3D and validated by comparing its result with the field data from literature. Then, parametric studies were conducted by controlling the ground stiffness, face pressure, tail void grouting pressure, and additional volume of muck discharge. As a result, the contribution of these operational factors to the surface settlement appeared differently depending on the ground stiffness. Except for the ground stiffness as the dominant factor, the order of variation of surface settlement was investigated, and the volume of additional muck discharge was found to be the largest, followed by the face pressure and tail void grouting pressure. The results from this study are expected to contribute to the development of settlement prediction models and understanding the surface settlement behavior induced by TBM excavation.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.148-163
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• 2021

Timely fault identification is important for safe and reliable operation of the electric valve system. Many research works have utilized different data-driven approach for fault diagnosis in complex systems. However, they do not consider specific characteristics of critical control components such as electric valves. This work presents an integrated shallow-deep fault diagnostic model, developed based on signals extracted from DN50 electric valve. First, the local optimal issue of particle swarm optimization algorithm is solved by optimizing the weight search capability, the particle speed, and position update strategy. Then, to develop a shallow diagnostic model, the modified particle swarm algorithm is combined with support vector machine to form a hybrid improved particle swarm-support vector machine (IPs-SVM). To decouple the influence of the background noise, the wavelet packet transform method is used to reconstruct the vibration signal. Thereafter, the IPs-SVM is used to classify phase imbalance and damaged valve faults, and the performance was evaluated against other models developed using the conventional SVM and particle swarm optimized SVM. Secondly, three different deep belief network (DBN) models are developed, using different acoustic signal structures: raw signal, wavelet transformed signal and time-series (sequential) signal. The models are developed to estimate internal leakage sizes in the electric valve. The predictive performance of the DBN and the evaluation results of the proposed IPs-SVM are also presented in this paper.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2743-2759
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• 2020

A detailed computational fluid dynamics (CFD) simulation analysis model was developed using ANSYS CFX 16.1 and analyzed to simulate the basic design and internal flow characteristics of a 180 MW small modular reactor (SMR) with a natural circulation flow system. To analyze the natural circulation phenomena without a pump for the initial flow generation inside the reactor, the flow characteristics were evaluated for each output assuming various initial powers relative to the critical condition. The eddy phenomenon and the flow imbalance phenomenon at each output were confirmed, and a flow leveling structure under the core was proposed for an optimization of the internal natural circulation flow. In the steady-state analysis, the temperature distribution and heat transfer speed at each position considering an increase in the output power of the core were calculated, and the conceptual design of the SMR had a sufficient thermal margin (31.4 K). A transient model with the output ranging from 0% to 100% was analyzed, and the obtained values were close to the T_hot and T_cold temperature difference value estimated in the conceptual design of the SMR. The K-factor was calculated from the flow analysis data of the CFX model and applied to an analysis model in RELAP5/MOD3.3, the optimal analysis system code for nuclear power plants. The CFX analysis results and RELAP analysis results were evaluated in terms of the internal flow characteristics per core output. The two codes, which model the same nuclear power plant, have different flow analysis schemes but can be used complementarily. In particular, it will be useful to carry out detailed studies of the timing of the steam generator intervention when an SMR is activated. The thermal and hydraulic characteristics of the models that applied porous media to the core & steam generators and the models that embodied the entire detail shape were compared and analyzed. Although there were differences in the ability to analyze detailed flow characteristics at some low powers, it was confirmed that there was no significant difference in the thermal hydraulic characteristics' analysis of the SMR system's conceptual design.

• 디지털정책학회지
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• 제1권2호
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• pp.17-24
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• 2022

중국에서는 코드 스캔 결제의 지속적인 홍보 및 적용으로 인해 코인 시장의 불균형이 발생되다. 동전 교환기는 이 문제를 완화할 수 있을 뿐만 아니라 상업 은행의 비즈니스 발생에도 적극적인 영향을 미친다. 따라서 동전 교환기를 연구하는 것은 매우 중요하다. 본 연극이 연극목적은 동전 교환기가 중국 상업 은행의 사업에 미치는 영향을 연구하는 것이다. 현장 방문을 통해 수집한 중국 상업 은행의 고객 데이터를 재무 지표 계산 방법과 결합하여 사례 분석을 수행한다. 연구 결과에 따르면 동전 교환기는 중국 상업 은행의 비즈니스 발전에 긍정적인 영향을 미친다. 본 연극는 중국 상업 은행에 대한 타당성 제안 및 비즈니스 개발에 대한 새로운 아이디어를 제공한다. 현재 동전교환기에 대한 연구는 거의 없으며, 본 연구는 재정지표 계산을 결합하여 정책성과를 검증하는 것이 본 연구의 혁신점이다.

• 문화기술의 융합
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• 제8권6호
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• pp.861-866
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• 2022

서울시에서는 공유 자전거 시스템, "따릉이"를 2015년부터 도입, 운영하여, 교통량 감축과 대기오염 해소를 위해 노력하고 있다. 하지만 공유 자전거 시스템, "따릉이"의 운영전략 미훕으로 인해 많은 문제가 발생하고 있어 이를 해결하고자 다양한 연구들이 제시되고 있다. 이들 연구의 대다수는 수요와 공급의 불균형을 해결하고자 하는 전략적 "자전거 배치"에 집중되어 있으며 또한 이들 중 다수가 날씨나 계절과 같은 특징을 그룹화함으로써 수요를 예측하고 있다. 그리고 이전에는 이들 예측방법이 주로 시계열 분석을 기반으로 하고 있었으나 최근에는 딥러닝/머신러닝으로 수요를 예측하는 연구들이 속속 등장하고 있다. 본 논문에서는 기존에 제시된 다양한 특징들을 기반으로 하면서, 새로운 특징을 발견하고 선택된 특징들의 중요도를 비교, 이를 순서화함으로써, 보다 정확한 수요 예측이 가능함을 보인다. 그리하여, 우리는 기존의 딥러닝/머신러닝 및 시계열 분석을 그대로 사용하면서 비교적 정확한 결정계수를 획득하고 이를 이용해 개선된 수요예측이 가능하도록 한다.

• 대한영양사협회학술지
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• 제28권4호
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• pp.227-246
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• 2022

This study was conducted on the nutritional status of 1,805 patients with allergic diseases (atopic dermatitis, allergic rhinitis, and asthma) aged 19 to 64 years according to their state of depression, based on the data from the Korea National Health and Nutrition Examination Survey (KNHANES). The Patient Health Questionnaire-9 (PHQ-9) was used to diagnose depression. Subjects with a score of 10 or more were categorized into the depression group (n=152) and the rest into the non-depression group (n=1,653). The results of this study were as follows: The proportion of women (75.7%) was higher than that of men (24.3%) in the depressed group (P<0.01). In terms of energy intake per 1,000 kcal, both men and women in the depressed group showed a lower energy intake than the non-depressed group and this intake was less than the estimated energy requirement (EER). The nutrient intakes of protein, calcium, phosphorus, iron, vitamin A, thiamine, riboflavin, niacin, folic acid, and vitamin C were below the estimated average requirement (EAR). Also, the intakes of fiber and potassium were less than the adequate intake (AI) (P<0.001). In the lifestyle parameters, the ratio of eating alone at lunch was 54.1%:33.1%, indicating that more than half of the depression group ate alone. In conclusion, it was observed that the nutritional status of allergic disease patients was imbalanced. The nutritional imbalance was due to insufficient energy intake and inadequate intake of nutrients, which was below the average requirements of vitamins and minerals and this was more evident in the depression group than in the non-depression group.

• 정보보호학회논문지
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• 제32권2호
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• pp.267-277
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• 2022

최근 클라우드 및 원격 근무 환경의 비중이 증가함에 따라 다양한 정보보안 사고들이 발생하고 있다. 조직의 내부자가 원격 접속으로 기밀 자료에 접근하여 유출을 시도하는 사례가 발생하는 등 내부자 위협이 주요 이슈로 떠오르게 되었다. 이에 따라 내부자 위협을 탐지하기 위해 기계학습 기반의 방법들이 제안되고 있다. 하지만, 기존의 내부자 위협을 탐지하는 기계학습 기반의 방법들은 편향 및 분산 문제와 같이 예측 정확도와 관련된 중요한 요소를 고려하지 않았으며 이에 따라 제한된 성능을 보인다는 한계가 있다. 본 논문에서는 편향 및 분산을 고려하는 부스팅 유형의 앙상블 학습 알고리즘들을 사용하여 악의적인 내부자 탐지 성능을 확인하고 이에 대한 면밀한 분석을 수행하며, 데이터셋의 불균형까지도 고려하여 최종 결과를 판단한다. 앙상블 학습을 이용한 실험을 통해 기존의 단일 학습 모델에 기반한 방법에서 나아가, 편향-분산 트레이드오프를 함께 고려하며 유사하거나 보다 높은 정확도를 달성함을 보인다. 실험 결과에 따르면 배깅과 부스팅 방법을 사용한 앙상블 학습은 98% 이상의 정확도를 보였고, 이는 사용된 단일 학습 모델의 평균 정확도와 비교하면 악의적인 내부자 탐지 성능을 5.62% 향상시킨다.

• 대한물리치료과학회지
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• 제29권4호
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• pp.27-42
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• 2022

Background: Although children with cerebral palsy (CP) are able to walk independently, gait imbalance occurs due to abnormal muscle tone, musculoskeletal deformity, loss of balance, and selective motor control impairment. Gait restriction in the community and school is a major problem of rehabilitation in CP. Home-based therapy (HBT) provides a variety of interventions in which the therapist and the parent work together to resolve the activities and problems caused by the child's body structure. Therefore, we investigate the effectiveness of home-centered therapy on gross motor function in CP and try to present the possibility of clinical application. Design: A Systematic Review Methods: Research papers were published from Jan, 2012 to Jan, 2022 and were searched using Medline and PubMed. The search terms are 'family-centered' OR 'home-based' AND 'cerebral palsy'. A total of nine papers were analyzed in this study. The paper presented the quality level based on Physiotherapy Evidence Database (PEDro) scores to assess the quality of randomized clinical trials studies. Results: The results showed that HBT for strengthening exercise in lower extremity has a positive effect on the isokinetic torque and gross motor function. home-based treadmill therapy in CP is effective to perform at least 12 sessions of treadmill HBP in which the therapist determines the treadmill speed every week and the child's own gait pattern is modified. Conclusion: These results suggest that it will be important data for founding evidence on the effectiveness of home-centered therapy on gross motor function in children with cerebral palsy to advance clinical protocols.

• Smart Structures and Systems
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• 제31권4호
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• pp.335-349
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• 2023

Bridges constantly undergo deterioration and damage, the most common ones being concrete damage and exposed rebar. Periodic inspection of bridges to identify damages can aid in their quick remediation. Likewise, identifying components can provide context for damage assessment and help gauge a bridge's state of interaction with its surroundings. Current inspection techniques rely on manual site visits, which can be time-consuming and costly. More recently, robotic inspection assisted by autonomous data analytics based on Computer Vision (CV) and Artificial Intelligence (AI) has been viewed as a suitable alternative to manual inspection because of its efficiency and accuracy. To aid research in this avenue, this study performs a comparative assessment of different architectures, loss functions, and ensembling strategies for the autonomous segmentation of bridge components and damages. The experiments lead to several interesting discoveries. Nested Reg-UNet architecture is found to outperform five other state-of-the-art architectures in both damage and component segmentation tasks. The architecture is built by combining a Nested UNet style dense configuration with a pretrained RegNet encoder. In terms of the mean Intersection over Union (mIoU) metric, the Nested Reg-UNet architecture provides an improvement of 2.86% on the damage segmentation task and 1.66% on the component segmentation task compared to the state-of-the-art UNet architecture. Furthermore, it is demonstrated that incorporating the Lovasz-Softmax loss function to counter class imbalance can boost performance by 3.44% in the component segmentation task over the most employed alternative, weighted Cross Entropy (wCE). Finally, weighted softmax ensembling is found to be quite effective when used synchronously with the Nested Reg-UNet architecture by providing mIoU improvement of 0.74% in the component segmentation task and 1.14% in the damage segmentation task over a single-architecture baseline. Overall, the best mIoU of 92.50% for the component segmentation task and 84.19% for the damage segmentation task validate the feasibility of these techniques for autonomous bridge component and damage segmentation using RGB images.

• 한국ITS학회 논문지
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• 제22권3호
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• pp.51-61
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• 2023

정확한 전동킥보드 중장기수요예측은 지역별 수요공급 불균형 문제해결 및 MaaS 등 연계교통체계 마련을 위해 필요하다. 공유 전동킥보드의 지역별 발생-유입량을 예측하는 연구는 많지만, 공유 전동킥보드의 존간 통행분포를 예측하는 연구는 전무한 실정이다. 본 연구에서는 공유 전동킥보드의 통행분포모형 추정을 위한 적정 존단위를 선정하고자 하였다. 분석 대상 존단위는 250m, 500m, 750m, 1,000m 정사각형 그리드로 설정하였다. 공유 전동킥보드 이용 이력 데이터는 각 공간 단위별 통행거리, 통행시간 계산 및 중력모형 도출을 위해 활용되었다. 평균제곱오차는 각 중력모형의 적정성을 검증하는데 활용되었다. 분석 결과, 250m 그리드가 실제 공유킥보드 통행분포를 가장 잘 묘사하는 것으로 나타났다.