• 한국시스템다이내믹스연구
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• 제8권1호
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• pp.117-149
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• 2007

This paper aims to analyse the impact of city-county consolidation on promotion practices of local government employees, using system dynamics approach. The cases employed in this study are Cheongju City and Cheongwon County which reached the referendum stage twice but without success. While the idea of consolidating two neighbouring local governments via a merger sounds enticing, some opponents argue that consolidation may cause some problems on the part of local government employees, emphasizing that consolidation could lengthen actual time period needed for local government employees' promotion. The majority of the existing literature on city-county consolidation, however, tends to describe the most successful cases, focusing on the achievements it has made or the political processes associated with it. With this in mind, this paper attempts to identify the impacts of consolidation on the local government employees' promotion time period, utilizing system dynamics approach. It concludes that consolidation could rather shorten the time period of promotion of local government employees concerned from the long term perspective.

• 한국시스템다이내믹스연구
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• 제14권1호
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• pp.31-53
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• 2013

The purpose of this study is to explain the impact of hosting mega event using the system dynamics and to establish the model for analysis of the impact of hosting mega event. The results are as follows. First, the growth of inbound tourists have influenced long term effect. Second, the export has increased for a limited period only after the hosting mega event, but the increase in export returned to the previous state in terms of economic impact of mega event. Third, nation brand has been improved for a limited period only such as the economical impact in terms of socio-cultural impact of mega event. Last, citizenship consciousness has been improved after hosting mega event. Further researches have to be carried out to modify and reinforce the model.

• Journal of Ecology and Environment
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• 제31권1호
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• pp.31-36
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• 2008

Larvae of the long-tailed clawed salamander, Onychodactylus fischeri, have a relatively long larval period, spending a year or more within the stream where they hatch; therefore, a well-established larval population could be critical for the conservation of adult populations. To study the population dynamics of long-tailed clawed salamander larvae, we surveyed a field population once or twice a month from September, 2005 to June, 2006, and determined the age of larval clawed salamanders collected from three different populations in October, 2004 using skeletochronology. The age of long-tailed clawed salamander larvae ranged from 0 to 3 years. New recruitment of larvae in the population primarily occurred in November, 2005, and mid-March, 2006. Larvae with a snout-vent length of more than 30 mm disappeared from the streams in September, 2005, suggesting that two to three year-old clawed salamander larvae metamorphosed during this period.

• 사회경제평론
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• 제38호
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• pp.51-83
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• 2012

다수의 상품이 생산되는 경제에서 스라파(Sraffa) 균형가격 조건과 균제성장 및 상품시장 균형 조건이 성립하는 경우를 생각하자. 이 모형에서 임금율 결정식과 투자함수를 동시에 부여하면 전체 경제는 과잉결정 되며 균형이 존재하지 않는다. 본 연구는 이 과잉결정 현상을 불균형 상태로 해석하고, 불균형상태에서 실현되는 임금율과 자본축적률이 각각의 동학식을 따라 결정되는 것으로 해석한다. 그리고 이 해석의 유효성을 주장하기 위하여 전체 경제에 대한 단순한 동학모형을 구축하고, 임금율과 자본축적률의 동학경로를 분석한다. 본 연구의 동학모형은 로카-볼테라 식체계의 구성조건을 만족하며, 따라서 전체 경제의 성장경로는 내생적으로 순환변동하는 경로를 따라 결정된다.

• 한국경영과학회지
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• 제29권2호
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• pp.19-43
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• 2004

This study was motivated by a practical need for estimating the macroeconomic effect of government IT Promotion investment, specifically for micro and small firms. Small firms have been in a disadvantageous position to adopt and utilize new IT compared with medium or large-sized firms. Small firms don't have enough resource to acquire IT in general, therefore private IT companies don't have much incentive to develop IT services and products for small firms. Lack of feasible IT solutions for small firms again restricted active IT adoption of small firms. Government recognized the vicious cycle, therefore decided to promote private IT companies to develop IT services and products for small firms's. Our main concern was to identify a relevant government supporting Policy, especially in the amount and the period. To do this, we first constructed a system dynamics simulation model to Investigate important factors and causal relationships among them. Simulation results showed 2.19% of GDP contribution and 0.16% of employment contribution in max from small firms' IT adoption. Also we could find that investing proper amount for a short period would be for better than maintaining Investing small amount for a long period.

• 한국농공학회논문집
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• 제61권1호
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• pp.1-8
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• 2019

Developing reliable soil moisture prediction techniques at agricultural regions is a pivotal issue for sustaining stable crop productions. In this study, a physically-based SWAP(Soil-Water-Atmosphere-Plant) model was suggested to estimate soil moisture dynamics at the study sites. ROSETTA was also integrated to derive the soil hydraulic properties(${\alpha}$, n, ${\Theta}_r$, ${\Theta}_s$, $K_s$) as the input variables to SWAP based on the soil information(Sand, Silt and Clay-SSC, %). In order to predict the soil moisture dynamics in future, the mid-term TIGGIE(THORPEX Interactive Grand Global Ensemble) and long-term S2S(Subseasonal to Seasonal) weather forecasts were used, respectively. Our proposed approach was tested at the six study sites of RDA(Rural Development Administration). The estimated soil moisture values based on the SWAP model matched the measured data with the statistics of Root Mean Square Error(RMSE: 0.034~0.069) and Temporal Correlation Coefficient(TCC: 0.735~0.869) for validation. When we predicted the mid-/long-term soil moisture values using the TIGGE(0~15 days)/S2S(16~46 days) weather forecasts, the soil moisture estimates showed less variations during the TIGGE period while uncertainties were increased for the S2S period. Although uncertainties were relatively increased based on the increased leading time of S2S compared to those of TIGGE, these results supported the potential use of TIGGE/S2S forecasts in evaluating agricultural drought. Our proposed approach can be useful for efficient water resources management plans in hydrology, agriculture, etc.

• Journal of Astronomy and Space Sciences
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• 제33권4호
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• pp.257-264
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• 2016

A planet revolving around binary star system is a familiar system. Studies of these systems are important because they provide precise knowledge of planet formation and orbit evolution. In this study, a method to determine the evolution of an exoplanet revolving around a binary star system using different rates of stellar mass loss will be introduced. Using a hierarchical triple body system, in which the outer body can be moved with the center of mass of the inner binary star as a two-body problem, the long period evolution of the exoplanet orbit is determined depending on a Hamiltonian formulation. The model is simulated by numerical integrations of the Hamiltonian equations for the system over a long time. As a conclusion, the behavior of the planet orbital elements is quite affected by the rate of the mass loss from the accompanying binary star.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2001년도 춘계 학술대회 논문집
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• pp.163-163
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• 2001

The primary research questions in this paper are why and how competing firms collaborate, not compete, in the virtual marketplace, e.g., B2B marketplace in the Internet environment. In order to answer the questions, we take on a system dynamics simulation approach: we consider two broad e-collaboration strategies: · Exclusive e-business strategy If the firm adopts this strategy, it allocates all of its resources (available for e-business development) to its own e-business capability building only. · Collaborative e-business strategy When the firm adopts a collaborative e-business strategy, it invests not only in its own, but also the industrys e-business capability building. From the system dynamics simulation results, we conclude that e-collaboration pays off in the long run: although it is hard to tell whether the collaborative strategy is better than the exclusive one during the initial period, it is unambiguous that the collaborative e-business strategy Performs much better in the long run. We infer that such collaboration could occur when the firms realize that they benefit from the expansion of the market demand due to their collaboration. That is, in order for such collaboration between competing firms to be sustainable, such collaboration should create more demand in the market so that each company could earn more profit even if it gets less in terms of market share.

• Animal cells and systems
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• 제2권2호
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• pp.217-222
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• 1998

Green peach aphid, Myzus persicae(Sulzer) (Homoptera: Aphididae), interacts with many predatory insects in potato fields during the summer. The concept of the predator complex associated with green peach aphids was applied to explain the interactions between the aphid and its predators. The predator power of the predator complex was determined by two factors: the number of predators and the relative feeding capacity. The dynamics of the green peach aphid population was expressed by the number of individuals while the predator power was used to characterize the predator complex. Cumulative degree-days for green peach aphids were used as a time scale to analyze phonology and dynamics patterns of the aphid and its predator complex. The patterns of population changes in aphids were similar during the period of study(1993-1995) although the highest density of aphids fluctuated significantly from year to year. However, the predator power appeared more stable than the green peach aphid population over the three year period. The results indicated that the predator complex plays an important role to suppress the aphid populations during the latter part of the season and that the applications of control measures for green peach aphids in between the initiation and the peak timing of aphid populations are critical to minimize the damage on potatoes.

• 한국토양비료학회지
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• 제48권6호
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• pp.641-647
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• 2015

Monitoring of soil fertility by long-term application of fertilizers is necessary to improve the fertility of soil and the productivity of crop. The objective of this study was conducted to investigate the changes of exchangeable Mg by continuous application of fertilizers from 1969 to 2014. The treatments were no fertilization (No fert.) and fertilization (NPK, NPK+C, NPK+S, and NPK+CS). The concentration of exchangeable Mg in No fert., NPK+C, and NPK+S treatments tended to increase from 1965 to 1975, but decrease gradually from 1976 to 1987, and increase again after 1988. Based on these, the changes of exchangeable Mg were divided into period I ('69 ~'75), period II ('76~'87), and period III ('88~'14). Especially, exchangeable Mg decreased in the period II. This was presumed that a significant amount of Mg from topsoil were leached into subsoil by break of plow pan and some of subsoil was incorporated into topsoil according to change of plowing depth by replacement of tillage machinery. It could be possible that exchangeable Mg in NPK, NPK+S, and NPK+CS was accumulated in the depth of 15~20 cm. For the period III, exchangeable Mg in No fert., NPK, NPK+C, NPK+S, and NPK+CS treatments increased at rates of 0.013, 0.018, 0.015, 0.023, and $0.024cmolckg^{-1}{\cdot}yr^{-1}$ respectively. Exchangeable Mg level in NPK+S was lower than the other treatments in the period I and period II, but higher than in the period III. This result was attributed to replacement of silicate fertilizer type from wollastonite (Mg 0.3%) to silicate fertilizer (Mg 3%). Also, exchangeable Mg level of No fert. treatment increased, which showed that Mg concentration of irrigated water had the greatest impact on Mg accumulation of soil. Recently, Mg level of irrigated water tended to increase, indicating that Mg concentration of water will affect greatly the concentration of exchangeable Mg of soil in the future. Like these, the changes of exchangeable Mg were greatly influenced by agricultural environment such as plowing depth, plow pan, content of fertilizer, and quality of irrigated water. Considering these agricultural environment, the proper management of soil is needed for the improvement of soil fertility and crop productivity.