• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.6
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• pp.475-484
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• 2012

Numerical investigation is performed to understand the effects of thickness uncertainty of a supporting airfoil due to manufacturing processes on the aerodynamic characteristics of an airfoil used for measuring data in a wind tunnel testing. This is done by comparing the coefficients of lift, drag and moment of the airfoils. In this work, the airfoil model consists of three parts, one located in the center for measuring and two outer parts used for supporting. The study is carried out with a NACA64-418 airfoil and the turbulence model of Transition SST. It is found that the effect of thickness uncertainty of the airfoils used for supporting is not significant to the performance of the test airfoil at various angles of attack and Reynolds numbers.

• KIISE Transactions on Computing Practices
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• v.21 no.7
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• pp.488-493
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• 2015

An AddSIM(Adaptive distributed and parallel Simulation environment for Interoperable and reusable Models) is an integrated engagement simulation environment with high-resolution weapon system models for estimation and analysis of their performance and effectiveness. AddSIM can simultaneously handle the continuous dynamical system models based on continuous time, and command, control(C2) and network system models based on a discrete event. To accommodate legacies based on DEVS(Discrete Event System Specification) modeling, DEVS legacies must first be converted into AddSIM models. This paper describes how to implement DEVS models on AddSIM. In this study a method of mapping from hierarchical DEVS models to AddSIM players was developed: The hierarchical DEVS model should be flattened into a one layered model and four DEVS functions of the model, external transition, internal transition, output and time advance, should be mapped into functions of the AddSIM player.

• Journal of Aerospace System Engineering
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• v.18 no.4
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• pp.18-26
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• 2024

This paper describes the results of a study on Generic Quad Tilt Rotor UAM aircraft, focusing on nonlinear mathematical modeling and the development of real-time simulation software. In this research, we designed a configuration for a Generic Quad Tilt Rotor eVTOL UAM aircraft based on NASA's UAM mission requirements. We modeled the aerodynamics using a database, the prop-rotor dynamics with a thrust database, and included a ground reaction and atmospheric model in the flight model. We defined the control concept for various modes(helicopter mode, transition mode, and airplane mode), derived tilt angle corridors, and formulated flight control requirements. The resultant real-time flight simulation software not only performs trim analysis for Tilt Rotor UAM aircraft but also predicts handling qualities, optimizes tilt angle scheduling based on dynamic characteristics, designs and validates flight control laws for helicopter, transition, and airplane modes, and facilitates flight training through simulator integration.

• Korean Journal of Environment and Ecology
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• v.26 no.3
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• pp.426-436
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• 2012

This study was carried out to investigate actual vegetation, the structure of plant community, and ecological succession sere of coastal forest ecosystem in warm temperate climate zone, Taejongdae, Busan City, Korea to provide the basic data for planning of the forest management. As a result of analysis of actual vegetation, vegetation types divided into 35 types, and the area of survey site was $1,750,461m^2$. The ratio of vegetation type dominated by Pinus thunbergii was 80.7%, dominated by Quercus spp. was just 5.0%, and dominated by Carpinus tschonoskii was just 0.4%. Eighteen plots(size is $20m{\times}20m$) were set up and the results analyzed by DCA which is one of the ordination technique showed that the plant communities were divided into four groups which are community I(P. thunbergii community), community II(P. thunbergii-Quercus serrata community), community III(Q. serrata-P. thunbergii community), and community IV(Carpinus tschonoskii-P. thunbergii community). The age of community I was from 38 to 59 years old, that of community II was from 35 to 71 years old, that of community III was from 37 to 53 years old, that of community IV was from 50 to 72 years old, thus we supposed that the age of the study site is about from 38 to 72 years old. We supposed that the successional sere of the study site is in the early stage of ecological succession in the warm temperate climate zone. The dominant species will be changed from P. thunbergii to Q. serrata or Carpinus tschonoskii in the canopy layer, on the other hand, Eurya japonica will be dominant species in the understory layer, and E. japonica and Trachelospermum asiaticum var. intermediumwill be dominant species in the shrub layer for a while. According to the index of Shnnon's diversity(unit: $400m^2$), community I ranged from 0.8640 to 1.3986, community II was from 0.1731 to 1.1885, community III was from 0.8250 to 1.0042, and community IV was from 0.3436 to 0.6986.

• Korean Journal of Environment and Ecology
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• v.27 no.3
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• pp.344-356
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• 2013

This study is a continuation of the 22 year consecutive study (1972~1993) to monitor community dynamics of forest in Mt. Kwanak. This study was intended to provide basic data for urban forest management in the future by analyzing actual changes in vegetation structure of forest in Mt. Kwanak caused by urban environmental changes. For the past 39 years (1972~2010), average temperature increased by approximate between 1.1 and $1.7^{\circ}C$ and soil acidification (pH $5.40{\rightarrow}4.50$) and contents of $K^+$ ($0.67{\rightarrow}0.25$) and $Ca^{{+}{+}}$ ($3.20{\rightarrow}0.87$) apparently tended to decrease. According to analysis importance percentage and DBH class of community types classified based on DCA, the succession stopped at Quercus mongolica for 39 years. In addition, the succession was expected to be held at Q. mongolica or to shift from Pinus densiflora to Q. mongolica and from Q. acutissima to Q. serrata. Size of trees growing in forest of Mt. Kwanak increased but the number of species and population of trees showed a downward trend for the 39 years and Styrax japonica and Sorbus alnifolia, which are indicator species, increased their dominance continuously. Decrease in contents of $K^+$, $Ca^{{+}{+}}$, and $Mg^{{+}{+}}$ and soil acidification for the past 39 years was found to affect degradation of vegetation structure in Mt. Kwanak.

• Korean Journal of Environment and Ecology
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• v.34 no.1
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• pp.27-41
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• 2020

The purpose of this study was to survey vegetation characteristics of Jeopdo (island) for the construction of a database. We installed and analyzed 52 plots with 100㎡ quadrat to investigate the vegetation characteristics. The community classification based on TWINSPAN found seven categories of vegetation communities in the surveyed region: Pinus thunbergii-Pinus densiflora community, Pinus densiflora-Quercus serrata community, Carpinus turczaninowii-Quercus variabilis community, Carpinus turczaninowii-Quercus acutissima community, Quercus variabilis-Carpinus turczaninowii community, Castanopsis sieboldii community, and Actinodaphne lancifolia-Camellia japonica community. The vegetation in Jeopdo is largely composed of evergreen conifer trees community (communities I and II), Carpinus turczaninowii-deciduous broad-leaved trees such as Quercus spp. community (communities III, IV, and V), and evergreen broad-leaved trees community (communities VI and VII). The evergreen conifer tree (Quercus serrata) community is currently competing with Pinus densiflora and Pinus thunbergii. The current state is expected to continue due to the lack of forces, such as Castanopsis sieboldii and Actinodaphne lancifolia, in the succession middle stage and climax stage. The current state of Carpinus turczaninowii-deciduous broad-leaved trees such as Quercus spp. community is expected to last for a long time due to slow vegetation development because of soil conditions. The evergreen broad-leaved trees community is transforming from the initial stage of Pinus densiflora and Pinus thunbergii through the stage in Quercus serrata to Castanopsis sieboldii and Actinodaphne lancifolia. The overall ages of the specimens were similar, and the oldest tree was the 59-year old Castanopsis sieboldii. The correlation analysis of major species showed a high positive correlation between Pinus thunbergii and Eurya japonica, Pinus densiflora and Fraxinus sieboldiana, and Actinodaphne lancifolia and Camellia japonica and a high negative correlation between Pinus densiflora and Carpinus turczaninowii and Carpinus turczaninowii and Eurya japonica.

• Korean Journal of Environment and Ecology
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• v.30 no.2
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• pp.228-242
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• 2016

This research was conducted for understanding the evergreen forest community structure of the Bijin Island. The island was worth of vegetational value because of the representative warm temperate species such as Castanopsis cuspidata was distribute there. According to the results of community classification by TWINSPAN and DCA, the Bijin Island evergreen forest were classified by 9 communities, such as C. cuspidata, C. cuspidata-Pinus thunbergii, Neolitsea sericea-Camellia japonica, Platycarya strobilacea, Quercus serrata-Decidus broad-leaved, Alnus firma, P. thunbergii. Due to the C. cuspidata, N. sericea, Ca. japonica etc. were still dominated at canopy and under-canopy layer, so the evergreen forest will be sustain current conditions for a while if there is no artificial disturbances that were caused by human. Pl. strobilacea community will be expected to replace N. sericea and also Q. serrata-Decidus broad-leaved community will be changing caused by mutual competition. Normally, in the way of the succession process of the warm temperate forest, P. thunbergii will be expect via deciduous broad-leaved to evergreen forest such as Machilus thunbergii, C. cuspidata var. sieboldii, and N. sericea. In case of species diversity index, P. thunbergii comm.(1.2739), Q. serrata-Decidus broad-leaved comm.(1.2325), Decidus broad-leaved comm.(1.1807), and A. firma comm.(1.0854) are relatively high, while C. cuspidata and N. sericea-Ca. japonica that was dominated by evergreen species at canopy layer and P. thunbergii that was damaged by fire are relatively low(0.7380~0.8416). Soil pH was 4.72~6.33, electric conductance was 0.035~0.128dS/m, and content of organic matter was 3.4~17.4%.

• Journal of Advanced Navigation Technology
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• v.21 no.4
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• pp.371-376
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• 2017

In this paper, we propose a magnetic resonant WPT(wireless power transfer) scenario using a large coil resonating at 6.78 MHz, and compare the characteristics through a three-dimensional electromagnetic field simulation and a magnetic resonant WPT equivalent circuit. The magnetic resonant WPT equivalent circuit proposed in this paper considers the parasitic capacitance generated between the coils in addition to the conventional equivalent circuit. Based on this analysis, we fabricated the magnetic resonant WPT coil and compared it with simulation prediction. As a result of comparison, the transfer characteristics and the resonance frequency shift can be predicted. Error proposed characteristics of equivalent circuit for the magnetic resonant WPT and the measured values are estimated to be ${\Delta}{\mid}S11{\mid}=1.31dB$ and ${\Delta}{\mid}S21{\mid}=1.21dB$, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.41-47
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• 2012

It is very important to predict the nonlinear behavior of combustion instability such as transition phenomena and limit cycle amplitude for fully understanding and controlling the instabilities. These nonlinear instability characteristics are highly dependent upon the flames' nonlinear dynamics in a gas turbine premixed combustor. In this study, nonlinear instability TA(Thermo-acoustic) models were introduced by applying the concept of flame describing function to the thermoacoustic analysis method. As a result of model development, for a given combustor length, the growth rate of instability was greatly affected by the change in amplitude, although the instability frequency was not. Further researches under various operating conditions and model validation on limit cycle amplitude are required.

• Korean Journal of Environment and Ecology
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• v.25 no.3
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• pp.365-377
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• 2011

This study aims at classifying and interpreting on the second forest vegetation located in Mt. Duryun affiliated to the ecotone in southern part of Korea, and foreseeing vegetation change based on component species and dominant species on canopy. The second forest vegetation is classified into 3 community units as Quercus serrata-Quercus variabilis community, Dendropanax morbiferus-Quercus acuta community and Chamaecyparis obtusa plantation. This research is also expatiated on the relationship between the distribution of communities and the environmental conditions. Quercus serrata-Quercus variabilis community will be succession horizontally and gradually from the part where Quercus variabilis is dominated relatively at first to the other part in the community, according to the component species of deciduous broad-leaved forest in the warm-temperate zone and evergreen broad-leaved forest as Camellietea japonicae.