• Journal of Korean Society of Forest Science
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• v.85 no.2
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• pp.260-270
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• 1996

Structure and dynamics of Pinus densiflora community in Mt. Kaya were studied to provide the information needed for management of Pinus densiflora forest in the southern inland of Korea. Stratification structure of Pinus densiflora community in the lower and middle slope consisted of tree layer(10~15m), subtree layer(4~10m), shrub layer(1~4m), and herb layer(below 1m), while in the rock zone of ridge and top area consisted of tree layer(7~10m), subtree layer(2~7m), shrub layer(1~2m), and herb layer(below 1m). According to the diameter distribution of tree species in Pinus densiflora community, secondary Pinus densiflora forest will gradually decline. Its forest may be replaced by Quercus mongolica, Quercus serrata, Carpinus laxiflora, C. cordata, and Fraxinus rhychophylla in the lower slope, and by Quercus mongolica in the middle slope. Pinus densiflora forest has its seedlings and saplings in ridge and top area, so it may be sustained. By taking cores from Pinus densiflora trees in research area, it could be obtained that in the lower and middle slope, age of Pinus densiflora forest was about 80~90 years old. When the age of its trees was about 72~80 years old, withering trees of standing dead occurred. Disturbance regime of Pinus densiflora community in Mt. Kaya consisted of standing dead, uprooting and limbfall, these were 70.6%, 17.6% and 11.8% respectively. It takes about 100~110 years for advance growth of Pinus densiflora in ridge and top area to reach tree layer. During the period, it has twice chances of disturbance in standing dead. Annual diameter growth of Pinus densiflora was 2.45~2.9mm in the lower and middle slope, while it was 1.75mm in ridge and top region, by measuring cores.

• Management & Information Systems Review
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• v.38 no.1
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• pp.121-139
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• 2019

This study aims to identify the change of customer participation(CP) which is essential to the service industry as the relationship between the customer and the employee develops. The latent growth modeling analysis based on the longitudinal data is utilized to examine the pattern of the change. This is based on the fact that CP needs to be understood in the relationship and is to confirm the change in CP by the development of the relationship. Given the dynamics of the relationship, we intend to overcome the limitations of previous cross-sectional researches by revealing the trajectory of CP in the relationship through the longitudinal data. We also want to examine which variables in the relationship can facilitate changes of CP. Research has shown that CP is significantly changed with the development of the relationship when we analyzed it through latent growth modeling. This confirms that CP needs to be understood in the relationship. In addition, 'relationship proneness' variable and 'dependence to provider' variable have positive effects on the initial values of CP, but they have not been established to promote the changes of CP. Consequently, when considering the dynamics of relationships, it is important to recognize that CP is also dynamic. This study sought to get out of the cross-sectional and fragmented understanding of CP that is dynamic. Through this, we would like to propose the successful operation of the customer management program of service firms in relation to CP. This will lead to the success of service encounter where appropriate CP levels at each stage of relationship development can be achieved.

• Journal of Korean Society of Forest Science
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• v.113 no.2
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• pp.143-152
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• 2024

This study was conducted to evaluate the growth and nutrient dynamics in response to fertilization of four tree species (LT: Liriodendron tulipifera L.; PY: Prunus yedoensis Matsumura; QA: Quercus acutissima Ca rruth; a nd PT: Pinus thunbergii Parl.) planted in a fire-disturbed urban forest in Bongdaesan (Mt.), Ulsan Metropolitan Area, South Korea. The trees were planted in 2009, and compound fertilizers (N₆P₄K₁) were applied in April 2013 and March 2014. Tree growth, soil, and foliage nutrients were examined from March 2013 to October 2016. The regression coefficients for the increment of the diameter at breast height (DBH) significantly differed between the fertilized and unfertilized plots, suggesting the significant effects of fertilization. By contrast, fertilization did not affect the coefficients for height increments. Regarding soil nutrient contents, organic carbon and total nitrogen concentrations were lower in the fertilized plots than in the unfertilized plots, whereas available phosphorus, exchangeable calcium, and magnesium concentrations were higher in the fertilized plots than in the unfertilized plots. In foliage, nitrogen and phosphorus concentrations were higher in the fertilized plots than in the unfertilized plots, whereas potassium, calcium, and magnesium concentrations were not affected by fertilization. Nutrient concentration of foliage among the tree species were higher in LT and PY than in QA and PT. These results suggest that fertilizers may be used to enhance soil fertility and the growth and nutrient status of tree species planted in a fire-disturbed urban forest.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.585-593
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• 2011

Actual fire test under a laboratory and fire simulation by using computer are considered into main methodology in order to estimate and predict fire size of railway train. Even if practical fire size could be obtained from the full-model railway car test such as a large scale cone-calorimeter test, it is not always possible and realistic due to that expensive cost and attendant dangers could in no way be negligible. In this point of view, fire simulation analysis method based on the computational fluid dynamics could be proposed as an alternative and it seems to be also efficient and reasonable. However, simulation results have to be verified and validated in accordance with the proper procedure including comparing analysis with the actual fire test. In this paper, fire load and growth aspect was investigated through the room corner test (ISO 9705) for the mock-up model of the actual railway car. Then, it was compared with the output data derived from the simulation by using Pyrolysis Model of the FDS (Fire Dynamics Simulator, by NIST) for the exact same domain and condition corresponding with pre-performed room-corner test. This preliminary verified and validated fire modeling method could enhance the reliability of output data derived from the fire simulation under the similar domain and condition.

• Korean System Dynamics Review
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• v.17 no.1
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• pp.5-24
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• 2016

This study structurally analyzes major inefficiency of Korea's healthcare delivery system by utilizing the systems thinking. In particular, the phenomenon of patient's concentrated visits to large hospitals, waste of resource due to competitions between clinics and large hopitals, and the structure of oversupply were visualized using the causal loop diagram. The inefficient structure of healthcare delivery system can be understood more clearly by utilizing the major system archetypes of 'success to the successful', 'tragedy of commons', 'escalation' and 'limits to growth'. This study also finds solution from archetypal structure suggested by Wolstenholme. The inefficient status of healthcare delivery system might be explained by the 'out of control' archetype. In conclusion, the public resources such as the national health insurance need to be acknowledged as the entire achievement. All the participants should cooperate with each other in order to improve the inefficiency of the healthcare delivery system. In addition, the arrangement of incentive system for cooperation, acceleration of health information technology, and development of innovative business models make the sustainable healthcare delivery system.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.2
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• pp.195-200
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• 2015

It is envisaged that the effect of increasingly stricter air emissions legislation implemented through IMO Annex VI and other local air quality controls, together with favorable financial conditions for the use of natural gas instead of liquid fuel oil as a bunker fuel, will see an increasing number of DF engine and single gas fuel engine applications to LNG carriers and other vessel types. As part of provision for the current international movements in the shipping industry to reduce GHG emission in air, new design concepts using natural gas as an alternative fuel source for propulsion of large commercial vessels, have been developed by shipyards and research institutes. In this study, an explosion analysis for a gas supply machinery room of LNG-fuelled container ship is presented. The gas fuel concept is employed for the high pressure ME-GI where a leakage in the natural gas double supply pipe to the engines is the subject of the present analysis. The consequences of a leak are simulated with computational fluid dynamics (CFD) tools to predict typical leak scenarios, gas cloud sizes and possible explosion pressures. In addition, capacity of the structure which is subject to explosion loads has been assessed.

• Journal of Powder Materials
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• v.15 no.1
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• pp.46-52
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• 2008

The restrictor, which is a fluid channel from a reservoir to a chamber inside a thermal micro actuator, has been fabricated using ArF and KrF excimer lasers, Diode-Pumped Solid State Lasers (DPSSL) and femtosecond lasers for a feasibility study. A numerical model of fluid dynamics for the actuator chamber and restrictor is presented. The model includes bubble formation and growth, droplet ejection through nozzle, and dynamics of fluid refill through the restrictor from a reservoir. Since an optimized and well-fabricated restrictor is important for a high frequency actuator, some special beam delivery setups and post processing techniques have been researched and developed. The effects of variations of the restrictor length, diameter, and tapered shapes are simulated and the results are analyzed to determine the optimal design. The numerical results of droplet velocity and volume are compared with the experimental results of a cylindrical-shaped actuator. It is found that the micro actuators having tapered restrictors show better high frequency characteristics than those having a cylindrical shape without any notable decrease of droplet volume. The laser-fabricated restrictors demonstrate initial feasibility for the laser direct ablation technique although more development is required.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.10 no.1
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• pp.113-121
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• 2014

In this work, an integrated model including molecular dynamics and chemical rate theory was implemented to calculate the growth of point defect clusters(PDC) and copper-rich precipitates(CRP) which could change the mechanical properties of reactor pressure vessel(RPV) steels in a nuclear power plant. A number of time-dependent differential equations were established and numerically integrated to estimate the evolution of irradiation defects. The calculation showed that the concentration of the vacancies was higher than that of the self-interstitial atoms. The higher concentration of vacancies induced a formation of the CRPs in the later stage. The size of the CRPs was used to estimate the mechanical property changes in RPV steels, as is the same case with the PDCs. The calculation results were compared with the measured values of yield strength change and Charpy V-notch transition temperature shift, which were obtained from the surveillance test data of Korean light water reactors(LWRs). The estimated values were in fair agreement with the experimental results in spite of the uncertainty of the modeling parameters.

• KIEAE Journal
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• v.10 no.2
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• pp.63-69
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• 2010

Diverse problems in wind environment has occurred through rapid urbanization and growth of high-rise building numbers, This study aims to propose the CFD (Computational Fluid Dynamics) simulation method and evaluation standard of wind environment in site planning of high rise apartment housing. The CFD simulation method proposed in this study is not existing detail simulation, but it is the method that a designer can correct and develop the design through immediate evaluation of design options in concept design phase. Therefore, the proposed CFD simulation method of wind environment in this study uses the BIM based CFD tool in which the 3D model in concept design phase can be used as for the CFD simulation. In this paper, the study examines existing evaluation standards of comfortableness level in wind environment for pedestrian near buildings, and selects new evaluation method which is possible to apply to the proposed CFD simulation method. In addition, it is to examine calculation time-spending and appropriate mesh division method for finding CFD result which is useful to find the best design options in aspect of wind environment in concept design phase. Furthermore, it proposes the wind environment evaluation method through BIM based CFD simulation.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.423-425
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• 2001

The Proper Orthogonal Decomposition (POD) technique was applied to investigate the effects of Reynolds number and the characteristics of the organized motions or coherent structures as a function of downstream position from x/D=2 to 6 in a turbulent axisymmetric shear layer at Reynolds numbers of 78,400, 117,600, and 156,800. Data were collected simultaneously using the 138 hot-wire probe used by Citriniti and George (2000). The POD was then applied to a double Fourier transform in time and azimuthal direction of the double velocity correlation tensor. The lowest azimuthal mode for all POD modes, which dominated the dynamics at x=D = 3 in the previous experiments, dies off rapidly downstream. This is consistent with a trend toward homogeneity in the downstream evolution, and suggests that some residual value may control the growth rate of the far jet. On the other hand, for the higher azimuthal modes, the peak shifts to lower mode numbers and actually increases with downstream distance. These mixing layer data, normalized by similarity variables for the mixing layer, collapse at all downstream positions and are nearly independent of Reynolds numbers.