• 한국수산과학회지
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• 제57권3호
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• pp.292-301
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• 2024

It is challenging to simultaneously estimate parameters in a stock-recruitment relationship, steepness, and natural mortality rate with the other parameters within an age-structured assessment model even in a data-rich situation. Such a problem leads to uncertainty in estimates of management references such as maximum sustainable yield (MSY), which are affected by those components. The objective of this study was to evaluate the effects of those parameters on MSY by analyzing the process of estimating the MSY. For illustration, we used two data sets: The chub mackerel Scomber japonicus in the Korean waters and the yellowtail flounder Limanda ferruginea in the Southern New England-Mid Atlantic. As a result, the natural mortality rate influenced spawning stock biomass per recruit, yield per recruit, and MSY, while steepness affected MSY. A sensitivity analysis enabled us to estimate the natural mortality rate and steepness. The optimal set of steepness and natural mortality was 1.0 and 0.37 per year for the chub mackerel, and 0.35, and 0.8 per year for the yellowtail flounder, respectively.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제13권1호
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• pp.1-11
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• 2009

Current therapies against ulcers caused by H. pylori infection consist of antibiotics, an acid reducer, and some clinical trials underway to develop a H. pylori vaccine. We develop a structured model with age-dependent mortality of peptic ulcers and H. pylori infection. Our main goal is to analyze our structured model mathematically and to compare it to our previously unstructured model to examine the disease transmission dynamics in terms of annual prevalence and annual incidence of the disease.

• 대한수학회논문집
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• 제18권1호
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• pp.133-149
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• 2003

Local stability of steady states of an epidemic model is considered. An age structured S-I-R epidemic model with separable inter-cohort force of infection with external force is considered. Stability result for the nontrivial steady states is obtained.

• Kyungpook Mathematical Journal
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• 제51권4호
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• pp.353-364
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• 2011

Duality in the optimal harvesting for a nonlinear age-spatial structured population dynamic model is studied in the framework of optimal control problem. In this paper the duality theory that displays the conjugacy of the primal problem is established and an application is given. Duality theory plays an important role in both optimization theory and methodology and the results may be applied to a realistic biological system on the point of optimal harvesting.

• Korean Journal of Radiology
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• 제21권7호
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• pp.869-879
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• 2020

Objective: To evaluate the performance of a convolutional neural network (CNN) model that can automatically detect and classify rib fractures, and output structured reports from computed tomography (CT) images. Materials and Methods: This study included 1079 patients (median age, 55 years; men, 718) from three hospitals, between January 2011 and January 2019, who were divided into a monocentric training set (n = 876; median age, 55 years; men, 582), five multicenter/multiparameter validation sets (n = 173; median age, 59 years; men, 118) with different slice thicknesses and image pixels, and a normal control set (n = 30; median age, 53 years; men, 18). Three classifications (fresh, healing, and old fracture) combined with fracture location (corresponding CT layers) were detected automatically and delivered in a structured report. Precision, recall, and F1-score were selected as metrics to measure the optimum CNN model. Detection/diagnosis time, precision, and sensitivity were employed to compare the diagnostic efficiency of the structured report and that of experienced radiologists. Results: A total of 25054 annotations (fresh fracture, 10089; healing fracture, 10922; old fracture, 4043) were labelled for training (18584) and validation (6470). The detection efficiency was higher for fresh fractures and healing fractures than for old fractures (F1-scores, 0.849, 0.856, 0.770, respectively, p = 0.023 for each), and the robustness of the model was good in the five multicenter/multiparameter validation sets (all mean F1-scores > 0.8 except validation set 5 [512 x 512 pixels; F1-score = 0.757]). The precision of the five radiologists improved from 80.3% to 91.1%, and the sensitivity increased from 62.4% to 86.3% with artificial intelligence-assisted diagnosis. On average, the diagnosis time of the radiologists was reduced by 73.9 seconds. Conclusion: Our CNN model for automatic rib fracture detection could assist radiologists in improving diagnostic efficiency, reducing diagnosis time and radiologists' workload.

• 대한수학회논문집
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• 제17권1호
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• pp.175-187
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• 2002

The existence and uniqueness of steady states for the age structured S-I-R epidemic model is considered. Intercohort form with external force is considered for the force of infection. Existence is obtained for nonvanishing external force of infection. Uniqueness is shown for the case where there is no vertical transmission of the disease.

• 수산해양기술연구
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• 제48권4호
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• pp.445-451
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• 2012

We developed an age-based spawner-recruit model incorporating environmental variables to forecast stock biomass and recruits of pelagic fish in this study. We applied the model to the Tsushima stock of jack mackerel, which is shared by Korea and Japan. The stock biomass of jack mackerel (Trachurus japonicus) around Korean waters ranged from 141 thousand metric tons (mt) and 728 thousand mt and recruits ranged from 27 thousand mt to 283 thousand mt. We hind-casted the stock biomass to evaluate the model performance and robustness for the period of 1987~2009. It was found that the model has been useful to forecast stock biomass and recruits for the period of the lifespan of fish species. The model is also capable of forecasting the long-term period, assuming a certain climatic regime.

• 성인간호학회지
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• 제27권6호
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• pp.684-694
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• 2015

Purpose: The purpose of this study was to explain fall prevention behaviors of community-dwelling elderly with osteoarthritis based on the Health Belief Model. Methods: A total of 200 older adults with osteoarthritis residing in community was recruited from July 10 to August 30, 2013. The direct and indirect effects of perceived fall risk, perceived benefits and barriers, and self efficacy of fall prevention were examined on fall prevention behaviors. Data were collected with structured questionnaires and analyzed using SPSS/WIN 20.0 and AMOS 20.0 program. Results: The hypothetical model was a good fit for the data based on the model fit indices. Among socio-demographic variables, age and fall knowledge showed significant direct effects on fall prevention behaviors. The constructed model explained 34.2% of the variance of fall prevention behaviors, including perceived fall risk and efficacy of fall prevention behaviors as significant predictors. Conclusion: The findings revealed the need to develop an effective nursing intervention to promote fall prevention behaviors of community-dwelling elderly with osteoarthritis by focusing on perceived fall risk and efficacy of fall prevention behaviors. Knowledge about fall can also be increased by an age-based education program.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 2006년도 춘계학술대회
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• pp.493-495
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• 2006

People frequently discuss equipment behavior in terms of time(age) and usage(mileage). Common examples are automobiles in which time and usageare usually included in discussion of longevity. In this paper a structured examination of bivariate measures of equipment utilization is performed and some useful model forms are developed and evaluated.

• 사회복지연구
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• 제44권3호
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• pp.57-83
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• 2013

본 연구는 과거의 노후 준비가 노년기에 이르러 활동적인 노년 생활을 보내는 것에 영향을 주는지, 그리고 노후준비를 통해 획득된 자기효능감 및 사회적 지지라는 심리사회적 자원이 이러한 두 요인간의 관계에서 매개효과를 가지는지 파악하는데 목적이 있다. 이를 위해 "2010 서울시 복지패널조사"자료 중 2010년도 가구원용 데이터를 분석 자료로 사용하였다. 연구 모형의 검증을 위해 빈도분석, 기술분석을 통해 대상자의 일반적 특성 및 주요 변수의 특성을 살펴보았고, AMOS 프로그램을 이용하여 모형의 적합도 분석 및 구조방정식으로 모형을 분석하였다. Sobel test를 통해 과거의 노후준비가 활동적 노화에 미치는 영향에 있어 심리사회적 자원인 자기효능감과 사회적 지지의 매개효과를 살펴보았다. 분석결과, 노후준비의 구성 요소인 신체적인 노후준비, 경제적 노후준비, 사회적 노후준비, 그리고 여가적인 노후준비는 활동적 노년생활에 정(+)적인 영향을 주는 것으로 밝혀졌다. 또한 과거의 노후준비와 노년기의 활동성의 관계에서 심리사회적 자원의 매개효과를 분석한 결과에서도 통계적으로 유의미한 영향력을 나타내어, 부분 매개 경로를 확인할 수 있었다. 연구결과를 통해, 노년기 진입에 앞서 다양한 영역에 대한 노후 준비는 심리사회적 자원을 획득하고 이는 활동적인 노후생활에 영향을 미치므로 복지정책을 개발함에 있어서도 향후 노후를 준비할 수 있도록 중장년층에게 노후준비 교육등을 실시하여 심리사회적 자원을 형성할 수 있도록 내용을 구성할 필요가 있다는 제언을 하고자 한다.