• Animal cells and systems
• /
• v.15 no.1
• /
• pp.73-78
• /
• 2011

Estimating the habitat potential of inland forest patches for birds requires the modeling of species-area relationships, or relationships between habitat size and numbers of bird species in each patch. The accurate estimation of speciesarea relationships significantly reduces the effort required to recognize the number of species living in each patch. The objective of this study was to estimate the relationship between forest patch size and bird species diversity in Dangjin County, in northwest South Korea, based on the sizes of inland forest patches. KOMPSAT-2 images were obtained and ortho-rectified to construct a map of the target forest patches. The numbers of birds per patch were surveyed four times: August 2008, September 2008, February 2009 and May 2009. Regression models were derived to explain the relationships between the numbers of bird species and patch size. A model that was derived using data from all four observation periods had the highest coefficient of determination ($R^2$). According to these models, the numbers of bird species at first increased linearly with increasing patch size; however, the curve then plateaued. Our model including observations from four seasons will be useful for estimating the numbers of bird species in other inland forest patches in South Korea.

• International Journal of Aeronautical and Space Sciences
• /
• v.18 no.3
• /
• pp.436-449
• /
• 2017

In this paper, the damage and failure behavior of triaxially braided textile composites was studied using progressive failure analysis. The analysis was performed at both micro and meso-scales through iterative cycles. Stress based failure criteria were used to define the failure states at both micro- and meso-scale models. The stress-strain curve under uniaxial tensile loading was drawn based on the load-displacement curve from the progressive failure analysis and compared to those by test and computational results from reference for verification. Then, the detailed failure initiation and propagation was studied using the verified model for both tensile and compression loading cases. The failure modes of each part of the model were assessed at different stages of failure. Effect of ply stacking and number of unit cells considered were then investigated using the resulting stress-strain curves and damage patterns. Finally, the effect of matrix plasticity was examined for the compressive failure behavior of the same model using elastic, elastic - perfectly plastic and multi-linear elastic-plastic matrix properties.

• Journal of the Korean Society of Industry Convergence
• /
• v.23 no.4_2
• /
• pp.611-616
• /
• 2020

Polycarbonate (PC) materials having electrical insulation properties, are thermoplastic material and are easily processed, have excellent strength and heat resistance characteristics, and also have transparent and hard characteristics. In this study, we tried to derive the ε-N curve of strain-life, which shows the relationship between the strain characteristics and the life of the material when repeated impact loads are applied to the PC plastic material. As the impact load increased to 3.0kg, 4.0kg, 5.0kg, and 6.0kg, the strain also increased linearly to 0.033, 0.041, 0.046, and 0.055. At 3.0kg of mass impact, the test piece broke with 12000 impact cycles, 8400 times at 3.5kg, 7400 times at 4.0kg, 6600 times at 4.5kg, 4700 times at 5.0kg, 3000 times at 5.5kg, and 1000 times at 6.0kg. The number of fractures exponentially decreased as the load gradually increased. Using these results, an ε-N curve for PC plastic was derived.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.19 no.3
• /
• pp.89-95
• /
• 2015

Performance test was conducted for an oxidizer pump and a fuel pump for a 7 ton class rocket engine, by using water. The pumps were driven by an electric motor. The hydrodynamic performance and the suction performance were measured at flow ratio of the design and off-design conditions. Head-flow curve, efficiency-flow curve, and head-cavitation number curve were obtained. It is confirmed that the pumps can satisfy the design requirements of hydrodynamic performance in terms of the head and the efficiency. The pumps also satisfied the design requirements of suction performance.

• Advances in biomechanics and applications
• /
• v.1 no.1
• /
• pp.1-14
• /
• 2014

In this paper, a simple and accurate finite element model coupled to quasi-brittle damage law able to describe the multiple cracks initiation and their progressive propagation is developed in order to predict the complete force-displacement curve and the fracture pattern of human proximal femur under quasi-static load. The motivation of this work was to propose a simple and practical FE model with a good compromise between complexity and accuracy of the simulation considering a limited number of model parameters that can predict proximal femur fracture more accurately and physically than the fracture criteria based models. Different damage laws for cortical and trabecular bone are proposed based on experimental results to describe the inelastic damage accumulation under the excessive load. When the damage parameter reaches its critical value inside an element of the mesh, its stiffness matrix is set to zero leading to the redistribution of the stress state in the vicinity of the fractured zone (crack initiation). Once a crack is initiated, the propagation direction is simulated by the propagation of the broken elements of the mesh. To illustrate the potential of the proposed approach, the left femur of a male (age 61) previously investigated by Keyak and Falkinstein, 2003 (Model B: male, age 61) was simulated till complete fracture under one-legged stance quasi-static load. The proposed finite element model leads to more realistic and precise results concerning the shape of the force-displacement curve (yielding and fracturing) and the profile of the fractured edge.

• Journal of Korean Society on Water Environment
• /
• v.27 no.1
• /
• pp.9-18
• /
• 2011

In this study the optimal volume for non-point source control retention is estimated considering spatio-temporal variation of land surface. The 3-parameter mixed exponential probability density function is used to represent the statistical properties of rainfall events, and NRCS-CN method is applied as rainfall-runoff transformation. The catchment drainage area is divided into individual $30m{\times}30m$ cells, and runoff curve number is estimated at each cell. Using the derived probability density function theory, the stormwater probability density function at each cell is derived from the rainfall probability density function and NRCS-CN rainfall-runoff transformation. Considering the antecedent soil moisture condition at each cell and the spatial variation of CN value at the whole catchment drainage area, the ensemble stormwater capture curve is established to estimate the optimal volume for an non-point source control retention. The comparison between spatio-temporally varied land surface and constant land surface is presented as a case study for a urban drainage area.

• Geomechanics and Engineering
• /
• v.30 no.4
• /
• pp.363-372
• /
• 2022

One of the most frequent issues in tunnel excavation is the collapse of rock blocks and the dropping of rock fragments from the tunnel face. The tunnel face can be reinforced using a number of techniques. One of the most popular and affordable solutions is the use of face longitudinal dowels, which has benefits including high strength, flexibility, and ease of cutting. In order to examine the reinforced face, this work shows the longitudinal deformation profile and ground response curve for a tunnel face. This approach is based on assumptions made during the analysis phase of problem solving. By knowing the tunnel face response and dowel behavior, the interaction of two elements can be solved. The rock element equation derived from the rock bolt method is combined with the dowel differential equation to solve the reinforced ground response curve (GRC). With a straightforward and accurate analytical equation, the new differential equation produces the reinforced displacement of the tunnel face at each stage of excavation. With simple equations and a less involved computational process, this approach offers quick and accurate solutions. The FLAC3D simulation has been compared with the suggested analytical approach. A logical error is apparent from the discrepancies between the two solutions. Each component of the equation's effect has also been described.

• Journal of Radiation Protection and Research
• /
• v.48 no.1
• /
• pp.20-27
• /
• 2023

Background: As the number of nuclear facilities nearing their pre-determined design life increases, demand is increasing for technology and infrastructure related to the decommissioning and decontamination (D&D) process. It is necessary to consider the nature of the dismantling environment constantly changing and the worker doing new tasks. A method was studied that can calculate the effect of learning and the change in work time on the work process, according to the learning-forgetting curve model (LFCM). Materials and Methods: The LFCM was analyzed, and input values and scenarios were analyzed for substitution into the D&D process of a nuclear facility. Results and Discussion: The effectiveness and efficiency of the training were analyzed. It was calculated that skilled workers can receive a 16.9% less collective radiation dose than workers with only basic training. Conclusion: Using these research methods and models, it was possible to calculate the change in the efficiency of workers performing new tasks in the D&D process and the corresponding reduction in the work time and collective dose.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.26 no.2
• /
• pp.59-69
• /
• 2022

The use of dampers is being considered a means to improve the seismic performance of buildings. It may take considerable time and effort to find an optimal design solution since repeated three-dimensional nonlinear time history analyses are required. Therefore, a preliminary design procedure for seismic retrofit using hysteretic dampers was proposed in this study. In the proposed procedure, the amount of retrofit (required number of dampers) is estimated from the capacity curve of the building before retrofit and allowable story drift of the building. In combining the capacity curves of the building and the dampers, the deformation demand for the dampers can be easily checked against their deformation capacity. The equations to transform the device displacement to roof displacement for the combination of capacity curves are developed. The proposed procedure was applied to the seismic retrofit design of sample buildings. The study found that the estimated capacity curve was very close to the actual capacity curve obtained from the pushover analysis, which can determine an appropriate configuration to meet the required seismic performance.

• The Journal of Asian Finance, Economics and Business
• /
• v.9 no.5
• /
• pp.295-303
• /
• 2022

This study investigates the impact of globalization, coal consumption, and economic growth on CO₂ emissions in Malaysia by applying the Kuznets Environmental Curve model. The study employed the Autoregressive Distributed Lag modeling technique on time series data over the period of 1970-2018 to determine the short and long-run relationship between CO₂ emissions and a number of variables, including globalization, coal consumption, and economic growth. The results show that globalization increase CO₂ emissions in both the short and long run in Malaysia. Furthermore, the results reveal that economic growth and coal consumption degrade the environmental quality by accelerating the CO₂ emissions in the short-run and long run. As a result, the findings validate the Kuznets Environmental Curve hypothesis of an inverted U-shaped relationship between economic growth and CO₂ emissions in the long run for Malaysia. The findings of this study suggest that higher globalization levels and usage of coal consumption degrade the environmental quality in Malaysia. The findings also indicate the effect of economic growth on environmental degradation is positive at the initial stage but improves after the economy achieves a threshold level of income per capita in the economic development process with an inverted U-shaped pattern in the long run.