• Journal of applied mathematics & informatics
• /
• 제27권3_4호
• /
• pp.779-793
• /
• 2009

This paper deals with a delayed SEIRS epidemic model with pulse vaccination and crowded incidence rate. Moreover, the case of vertical and horizontal transmission is considered. By using the discrete dynamical system determined by the stroboscopic map, the exact infection-free periodic solution of the SEIRS model is obtained. Further, by employing the comparison arguments, we prove that under the condition that $R_*$ < 1 the infection-free periodic solution is globally attractive, and that under the condition that $R^*$ > 1 the disease is uniformly persistent, which means that after some period of time the disease will become endemic.

• The Journal of Asian Finance, Economics and Business
• /
• 제10권1호
• /
• pp.31-40
• /
• 2023

This paper investigates the effect of independent directorship on the firm performance of Chinese listed companies under the impact of the global COVID-19 epidemic. The study starts by assessing the relationship between independent director-related characteristics and firm performance, then mines independent director characteristics variables, collects variable data, proposes reasonable hypotheses, and constructs a data model. 1597 companies listed on Shanghai and Shenzhen stock index, China, from 2020 to 2021 has been selected as the research sample. An empirical study on the relationship between independent directors' characteristics and firm performance was conducted using SPSS25. The results show that under the impact of the global COVID-19 epidemic, the proportion of independent directors on the board of directors, the age of independent directors, the remuneration of independent directors, and the overseas background of independent directors in Chinese listed companies have a negative relationship with the current firm performance, while the proportion of female independent directors and the part-time rate of independent directors do not have a positive effect on firm performance. The findings of this study strongly imply that independent directors' characteristics play a significant role in corporate governance and firm performance in Chinese listed companies and that the external environment has an impact on how well independent directors can carry out their duties.

• 한국시스템다이내믹스연구
• /
• 제14권4호
• /
• pp.37-62
• /
• 2013

The purpose of this paper is to find out some clues about effectiveness and implementing timing of the control measures against Foot-and-Mouth Disease (FMD) in Korea. To do that, the case of FMD, which broke out during November 2010 in Korea, is examined and constructed as a system dynamics simulation model. The implications of simulation result are as follows. First of all, it is most effective measure to prevent the movement of vehicle from infected farmhouse to other noninfected farmhouses, which are located far away, in the early stage of FMD diffusion. Secondly, earlier vaccination can be adopted as a reliable means to control the epidemic when FMD spreads widely. Finally, reducing the time to vaccinate the whole noninfected livestock is a little help to restrain the additional infections of FMD.

• 대한예방의학회:학술대회논문집
• /
• 대한예방의학회 2005년도 제57차 추계 학술대회 연제집
• /
• pp.489-489
• /
• 2005

• Journal of Veterinary Science
• /
• 제23권1호
• /
• pp.2.1-2.18
• /
• 2022

Background: Co-infections of the porcine reproductive and respiratory syndrome virus (PRRSV) and the Haemophilus parasuis (HPS) are severe in Chinese pigs, but the immune response genes against co-infected with 2 pathogens in the lungs have not been reported. Objectives: To understand the effect of PRRSV and/or HPS infection on the genes expression associated with lung immune function. Methods: The expression of the immune-related genes was analyzed using RNA-sequencing and bioinformatics. Differentially expressed genes (DEGs) were detected and identified by quantitative real-time polymerase chain reaction (qRT-PCR), immunohistochemistry (IHC) and western blotting assays. Results: All experimental pigs showed clinical symptoms and lung lesions. RNA-seq analysis showed that 922 DEGs in co-challenged pigs were more than in the HPS group (709 DEGs) and the PRRSV group (676 DEGs). Eleven DEGs validated by qRT-PCR were consistent with the RNA sequencing results. Eleven common Kyoto Encyclopedia of Genes and Genomes pathways related to infection and immune were found in single-infected and co-challenged pigs, including autophagy, cytokine-cytokine receptor interaction, and antigen processing and presentation, involving different DEGs. A model of immune response to infection with PRRSV and HPS was predicted among the DEGs in the co-challenged pigs. Dual oxidase 1 (DUOX1) and interleukin-21 (IL21) were detected by IHC and western blot and showed significant differences between the co-challenged pigs and the controls. Conclusions: These findings elucidated the transcriptome changes in the lungs after PRRSV and/or HPS infections, providing ideas for further study to inhibit ROS production and promote pulmonary fibrosis caused by co-challenging with PRRSV and HPS.

• 자원ㆍ환경경제연구
• /
• 제30권1호
• /
• pp.27-48
• /
• 2021

본 연구는 코로나19 확산에 대응한 최적 방역정책이 국내 거시경제에 미치는 동태적 효과를 분석하였다. 백신, 치료제, 사회적 거리두기의 다양한 조치가 취해지는 상황에서 감염병 예방노력의 도덕적 부주의를 결합한 거시-역학 모형을 제시하였다. Eichenbaum, Rebelo and Trabandt(2020)의 거시-역학 모형에 도덕적 부주의 상황을 추가하였으며, 확산모형을 이용하여 국내의 코로나19 감염율을 추정하였다. 사회적 후생을 극대화하는 램지 문제의 동태적 분석결과는 사람들의 일상 중 생활속 거리두기 준수가 정부의 방역정책과 치료제, 백신 도입이 효과를 발휘하는 데 매우 중요한 역할을 한다는 점을 시사한다. 도덕적 부주의가 있는 경우의 최적 방역정책은 2배 더 강화되어야 하며, 총소비는 7% 하락하고, 회복하는 데 저점부터 12주가 소요된다. 백신과 치료제 개발에 성공하는 데 평균 13주 소요되는 경우에 총소비는 2% 하락하는 것으로 도출되었다.

• Journal of applied mathematics & informatics
• /
• 제30권3_4호
• /
• pp.635-646
• /
• 2012

This paper is concerned with an SIRS epidemic model with spatial diffusion and time delay representing the length of the immunity period. By using a new cross iteration scheme and Schauder's fixed point theorem, we reduce the existence of traveling wave solutions to the existence of a pair of upper-lower solutions. By constructing a newfashioned pair of upper-lower solutions, we derive the existence of a traveling wave solution connecting the uninfected steady state and the infected steady state.

• Nutrition Research and Practice
• /
• 제4권6호
• /
• pp.528-534
• /
• 2010

This study explores the influence of health behaviors and individual attributes on adolescent overweight and obesity using data from Wave II (Add Health). Structural equation model/ path analysis using maximum likelihood estimation was utilized to analyze the relationships of health behaviors and attributes with obesity. Results of the model reveal that the causal paths (adolescents' attributes and health behaviors) for overweight and obesity were different for African American and Caucasian adolescents. Generally, African Americans were more susceptible to overweight and obesity than Caucasians. Although increasing levels of vigorous physical activities lowers the risk for obesity among African American and Caucasian adolescents alike, low family SES and being sedentary were associated with overweight and obesity among Caucasians. No significant associations were found among African Americans. Increased hours of sleep at night relate positively with obesity among African Americans. These findings suggest important elements in the consideration of race in developing effective intervention and prevention approaches for curbing the obesity epidemic among U.S. adolescents.

• 대한의용생체공학회:의공학회지
• /
• 제9권2호
• /
• pp.159-164
• /
• 1988

This thesis investigates the Quantitative aspect of epidemic phenomena utilizing the analytical method of discrete time systeMs based on the theory of Markov processes. In particular, the pattern on the epidemic character of turberculosis controlled by prophylaxis and BCG vaccinatioll was analyzed by the markovian model of tuberculosis system which is derived according to the ecologic relationship between nine epidemiologic states of individuals. The quantitative aspects of the model were characterized by digital computer simulations.

• 한국컴퓨터정보학회:학술대회논문집
• /
• 한국컴퓨터정보학회 2015년도 제52차 하계학술대회논문집 23권2호
• /
• pp.81-83
• /
• 2015

본 연구는 사용자의 감성이 온라인 소셜 미디어를 통해 감염이 된다는 사실을 감성 전파 모델링으로 보이고자 한다. 이를 위해 전염병 파생을 기술하고 이를 예측하는데 사용되었던 질병확산 모델을 기초로 소셜 미디어상의 감성 전파 모델을 제시한다. 제시한 모델의 타당성을 검증하기 위해 특정 리테일 산업에 대한 논의가 활발히 이루어지고 있는 웹포럼의 데이터를 수집한다. 수집된 데이터로부터 주요 주제어를 도출하고, 주제별 감성을 측정하고, 시간에 따른 감성 값을 도출하여, 제시한 모델을 추정한다. 실험 결과 사용자의 긍정적 감성과 부정적 감성이 서로 경쟁관계에 있다는 가정을 따른 제안한 모델이 타당함을 보였다.