• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.3
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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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• v.13 no.1
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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.

• Communications of the Korean Mathematical Society
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• v.18 no.1
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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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• v.51 no.4
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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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• v.21 no.7
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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.

• Communications of the Korean Mathematical Society
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• v.17 no.1
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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.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.4
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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.

• Korean Journal of Adult Nursing
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• v.27 no.6
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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.

• Proceedings of the Korean Society for Quality Management Conference
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• 2006.04a
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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.

• Korean Journal of Social Welfare Studies
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• v.44 no.3
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• pp.57-83
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• 2013

There has neither been enough research on how to approach the concept of active aging through an integrated view nor an examination to verify the relationship between preparation for old age and active aging in later life. Therefore, this research aims to verify that the elderly, who have prepared for their later life, affected their active aged life. In addition, by setting up self-efficacy and social support as mediator in the research model, this paper looks into the psycho-social resource mechanism of the relationship in depth. In order to verify the correlation of two variables, the Seoul welfare panel data, a mediating model structured by psycho-social resources created by Seoul welfare foundation in 2010, was used. The total sample size was a group of 1,492 elders aged over 65. When it came to our research methods, structured equation analysis was applied to verify the mediating effect and theoretical background. The results revealed that physical preparation, financial preparation, social preparation and leisure preparation directly affected their active aging level positively, thus, psycho-social resources showed a partial mediating effect between preparation for old age of the past and active aging level. The research implications are as follows. First, this research makes an effort to approach the concept of preparation for old age with an integrated perspective through making a construct by entire preparation types. Second, it will attempt to verify the relationship between preparation for old age in the past and active aging in terms of multi-dimension is meaningful. Third, this research reveals the function of psycho-social resource, self-efficacy and social support within the relationship. As far as the partial mediating effect is concerned, preparation for old age education for the middle-aged class should be modified as a decent field to enhance of the elderly.