A Study on Pressure Control in Fuel Cell Stack of Electric Propulsion Ship using Neural Networks

최근 국내외적으로 선박에서 발생되는 해양 대기오염 배출 문제를 해결하기 위해 대체연료를 사용하는 친환경 추진시스템에 관한 연구가 활발히 진행되고 있다. 그 중 수소를 사용하는 연료전지를 활용한 전기추진시스템에 대한 연구 및 실증이 활발히 이루어지고 있다. 선박에 적용된 수소연료전지는 셀의 손상을 고려하여 급격한 전력 변동을 최소화하는 전력관리시스템이 적용되어 시스템 제어 로직이 비교적 복잡하고 함께 사용되는 배터리의 역할이 크다. 본 논문에서는 연료전지시스템을 전기추진선박의 주전원에 적용하기 위해 선박의 부하 변동에도 연료전지 스택의 내부 압력을 안정적으로 유지하기 위해 속응성과 안정성을 갖춘 수소연료 및 공기공급 제어기를 제안하고 시뮬레이션을 통해 유효성을 확인하였다.| Recently, studies on propulsion systems using alternative fuels are being actively conducted to solve international marine air pollution problems and greenhouse gas problems. Among them, research and demonstration of electric propulsion systems using hydrogen fuel cells are being actively conducted. The hydrogen fuel cell applied to the ship uses a power management system that minimizes load fluctuations, so the system control logic is relatively complex and the battery used together plays a large role. In this paper, in order to apply the fuel cell system to the ship's main power source, hydrogen fuel and air supply controller for PEMFC fuel cell with quick response and stability in the ship's load fluctuation was proposed, and its validity was confirmed through simulation.제 1 장 서론 1 1.1 연구배경 1 1.2 연구내용 2 1.3 논문의 구성 3 제 2 장 연료전지 제어시스템이 적용된 전기추진선박 4 2.1 연료전지 발전원을 갖는 전기추진시스템 4 2.1.1 고분자 전해질 연료전지 (PEMFC) 5 2.1.2 배터리 6 2.1.3 직류배전시스템 6 2.1.4 전력변환장치 7 2.2 PEMFC 제어시스템 8 제 3 장 신경회로망 개요 10 3.1 신경회로망의 생물학적 구조 10 3.2 신경회로망의 구성요소 및 동작특성 11 3.3 다층구조의 신경회로망 구조와 동작특성 11 3.4 오류역전파학습 알고리즘 12 제 4 장 신경회로망을 이용한 연료전지 스택 압력 제어시스템 14 4.1 PEMFC 모델링 15 4.1.1 양극과 음극의 내부 압력 모델 15 4.1.2 전압 모델 18 4.1.3 다중입력 다중출력 피드백 선형화제어기법 20 4.1.4 출력제어기 24 4.4 신경회로망을 이용한 연료전지 스택 압력 제어시스템 26 제 5 장 시뮬레이션 42 5.1 기존 연료전지 스택 압력 제어시스템 44 5.1.1 시뮬레이션 Case 1 48 5.1.2 시뮬레이션 Case 2 50 5.2 신경회로망을 이용한 연료전지 스택 압력 제어시스템 56 5.2.1 시뮬레이션 Case 1 59 5.2.2 시뮬레이션 Case 2 61 제 6 장 결론 66 참고문헌 68Maste

Initial Characteristics and Clinical Severity of Hemophagocytic Lymphohistiocytosis in Pediatric Patients Admitted in the Emergency Department

Objectives The diagnosis and management of children with hemophagocytic lymphohistiocytosis (HLH) admitted in the emergency department (ED) are challenging. The present study aimed at describing the initial characteristics of pediatric patients with HLH upon admission in the ED. Moreover, the clinical severity of the condition was assessed. Methods We performed a retrospective study of patients who visited the pediatric ED and were newly diagnosed with HLH during hospitalization between February 2012 and January 2017. The patients were classified in the clinically unstable group if at least 1 of the following conditions was observed upon admission in the ED: hypoxia requiring oxygen supplementation, hypotension requiring inotropic support, coagulopathy with prothrombin time (international normalized ratio, >= 1.5), and seizures or altered consciousness. Results We enrolled 31 pediatric patients with HLH, with a median age of 6.53 years (interquartile range, 1.35-13.24 years). Abdominal discomfort along with fever (74.2%) was the most common presenting symptom in patients admitted in the ED. Based on the HLH-2004 diagnostic criteria, fever (96.8%), hyperferritinemia (96.8%), splenomegaly (74.2%), hypertriglyceridemia and/or hypofibrinogenemia (67.7%), and bicytopenia (41.9%) were observed in the patients. However, only 8 patients (25.8%) met the criteria. Nineteen patients (61.3%) were included in the clinically unstable group. This group had lower albumin (2.3 vs 3.3 g/dL, P = 0.002) and fibrinogen levels and higher ferritin level and neutrophil count than the clinically stable group. Meanwhile, the number of clinical findings that met the diagnostic criteria was not different between the 2 groups. Lower albumin level was a significant risk factor in the clinically unstable group (odds ratio, 0.040; P = 0.004). Conclusions Pediatric patients with HLH often have clinically unstable conditions upon admission in the ED. However, only few patients meet the HLH-2004 diagnostic criteria. Lower albumin level may be useful in assessing clinically unstable patients and preparing for possible deterioration