• Korean System Dynamics Review
• /
• v.5 no.2
• /
• pp.67-88
• /
• 2004

This paper attempts to explore the generic pitfalls of the traditional number-crunching methods adopted thus far for the forecast of newly emerging market trends, and present an alternative by introducingsystems thinking to the portable Internet service market as an example, followed by its rationale as a new tool for forecasting and some reasoning about why traditional methods are no longer appropriate. Most adoption models in general to forecast market trends have several limitations due to theirbasic assumptions and prospective. First, they fail to capture dynamic interactions among the factors involved over time, with implicit assumptions of 'unilateral causality' in that each factor contributes as a cause to the effect, i.e., causality runs one way; each factor acts independently the weighting factor of each is fixed, etc. Second, the number-crunching models have no way of taking into account the impact of delayed feedback often caused by introducing new policies and legislative changes on the whole system under investigation. Third, there is not a way to reflect the effect of competition by players.

• Journal of Construction Engineering and Project Management
• /
• v.3 no.2
• /
• pp.13-20
• /
• 2013

Construction industry has become a larger and highly competitive industry. A successful construction project cannot be achieved only by efficient and fast construction techniques but also reasonable material cost and adequate transferring time of materials to installation. The steel industry in East Asia has become the mainstream in overall steel industries in over the world during the middle of the 21st century. China, Japan and Korea has been the main exportation countries. However, even though the international economic failure, China has increased the exportation amount and became an only exporting country which must be considered a serious problem regarding competitiveness in the international steel exportation industry. Thus, this study analyses the factors affecting the supply and demand amount of reinforced bars in the domestic field and moreover suggesting a unit cost prediction model using the System Dynamics simulation methodology, one of powerful prediction tools using cause-effect relationships. It is expected that this study contributes to the domestic steel industry growth in competitiveness in the international industry. In addition, the methodology used in this paper presents the frameworks for appropriate tools for market trend analysis and prediction of other markets.

• Korean System Dynamics Review
• /
• v.11 no.3
• /
• pp.33-59
• /
• 2010

South Korea has the defense burdensharing agreement with the United States in reference to the U.S. troops stationed in Korea since 1991, based on Special Measure Agreement(SMA). Due to the growth of Korea's economic power and the U.S. provision of the security environment on Korean penninsula, the U.S. government steadily demanded the rise of contributions to common defense from South Korea and South Korea accepted most of the U.S. requests without proper principles of negotiation concerning the cost sharing. This paper analyzes the systems of the Korea－U.S. cost sharing program through a systems thinking, that yields desirable results with a little effort. The three policy leverages are: 1) the development of negotiation principles; 2) the policy making closely linked with National Defense Reform Basic Plan; 3) the policy making with responsibility burdensharing than cost burdensharing. This paper findings will contribute to the developing the Korea－U.S. cost sharing program by providing policy－makers and policy-practitioners with systematic understanding and insight into the dynamics of the program. Also, this will enable the program to execute more effectively with a concrete formula.

• Korean System Dynamics Review
• /
• v.7 no.1
• /
• pp.5-26
• /
• 2006

Ever increasing dependence of organization on information technology stimulates interactions between individuals and groups in the process of knowledge creation, which overall impies that a reciprocal mechanism lies within the structure of the growth of group intelligence. Individual's intelligence may affect the group intelligence, and vise versa. However, the level of group intelligence is not necessarily determined by the sum of individual's intelligence but the quality of the interactions among the individuals. This study thus aims to conceptually identify the dynamic structure of interactions among the factors influencing the group intelligence level, which is believed to be used as a tool to measure the difference of intelligence between groups. To achieve this goal several attempts were made. First, determinants of intelligence at indiviual level and group level and similarities and differences between individual's and group intelligence were identified from the previous research. Second, causal loop diagrams were developed, which show how individual's intelligence influences group intelligence and vise versa. Third, it was attempted to identify and interpret which feedback loops are most influential in either improving or hapering group intelligence as a whole. Since this study remains only at exploratory level, a more detailed and workable model for field applications has to be developed in the future.

• International Journal of Control, Automation, and Systems
• /
• v.2 no.3
• /
• pp.374-383
• /
• 2004

This paper presents a neural network adaptive controller for autonomous diving control of an autonomous underwater vehicle (AUV) using adaptive backstepping method. In general, the dynamics of underwater robotics vehicles (URVs) are highly nonlinear and the hydrodynamic coefficients of vehicles are difficult to be accurately determined a priori because of variations of these coefficients with different operating conditions. In this paper, the smooth unknown dynamics of a vehicle is approximated by a neural network, and the remaining unstructured uncertainties, such as disturbances and unmodeled dynamics, are assumed to be unbounded, although they still satisfy certain growth conditions characterized by 'bounding functions' composed of known functions multiplied by unknown constants. Under certain relaxed assumptions pertaining to the control gain functions, the proposed control scheme can guarantee that all the signals in the closed-loop system satisfy to be uniformly ultimately bounded (UUB). Simulation studies are included to illustrate the effectiveness of the proposed control scheme, and some practical features of the control laws are also discussed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.2
• /
• pp.757-769
• /
• 2013

Intangible assets for construction engineering consulting firms are very important for their valuation, because engineering consulting is typical knowledge-based business which creates value based on technical expertise and human resources. This paper presents the intangible asset classification model based on the concept of value creation in construction engineering consulting firm and proposes intangible asset valuation methodology using System Dynamics and survey data. Utilization of the valuation methodology presented in this paper would increase the public awareness of intangible assets in construction engineering consulting firm and, thus, contribute to the growth of the engineering consulting industry by realistic and accurate valuation of intangible assets.

• The Journal of Information Systems
• /
• v.15 no.4
• /
• pp.99-124
• /
• 2006

The development of IT has made it possible to use various terminal systems for financial transaction and demands for financial survices are getting more and more diversified at the same time. Among others, mobile banking service market based on IC chips has been expanded its service areas and the number of mobile banking users has been increased. The study analyzes and tests the dynamic effects of the inflow of potential customers on mobile banking market condition by using system dynamics methodology to identify the dynamic structure of mobile banking market. The simulation model is designed to track the variation in the number of subscribers of mobile banking servides according to two scenarios, and the results are as follows; First the effect of word of mouth by customers who have used the service already is significant. The satisfactory level of early adopters is reflected in WOM, and as a test result shows, increase in word-of-mouth causes the growth of potential customers' demands for mobile banking service. Second, perceived attractiveness of mobile banking service market is another important construct. Factors such as convenience, mobility, time saving, security, and various services explain the construct perceived attractiveness of the service, and it makes the potential customers adopt the service, causing the increase of demands.

• Wind and Structures
• /
• v.36 no.3
• /
• pp.215-220
• /
• 2023

We study the progressive full-scale wind tunnel tests on a high solidity vertical axis wind turbine (VAWT) for various tip speeds and pitch angles to understand the VAWT shaft system's dynamics using 0-1 Test for chaos. We identify that while varying rotor speed (tip speed) of the turbine, the system's dynamics change from periodic to chaotic through quasiperiodic and strange non-chaotic (SNA) states. The present study is the first experimental evidence for the existence of these states in the VAWT shaft system to the best of our knowledge. Using the asymptotic growth value Kc in 0-1 test, when the turbine operates at the low tip speeds and high pitch angles for low incoming wind speeds, the system behaves periodic (Kc ≈ 0). However, when the incoming wind speed increases further the system's dynamics shift from periodic to chaotic vibrations through quasi-periodic and SNA. This phenomenon is due to the dynamic stalling of blades which induces chaotic vibration in the VAWT shaft system. Further, the singular continuous spectrum method validates the presence of SNA and differentiates the SNA from chaotic vibrations.

• Proceedings of the Korea Association of Information Systems Conference
• /
• 2004.05a
• /
• pp.316-335
• /
• 2004

This paper builds a system dynamics model analyzing first mover effect and growth strategy of online retailer, a major segment of B2C e-commerce. The dynamic model in this paper is calibrated to the online book market and Yes24.com as major test cases. The model consists of eight key value chain sectors. Five of these(Users, Site Operations, Human Resources, Financial Accounting, and Fundraising) are internal to the company, and three others(Market, Financial Market, and Relative Performance) are external to the company. With the model, this paper suggests research propositions representing positive feedback loops and negative feedback loops that lead to corporate growth and limits to growth according to dynamic causal relationships among eight key value chain sectors, and simulate these propositions.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.32 no.2
• /
• pp.125-132
• /
• 2008

The bubble dynamics and heat transfer associated with nucleate boiling in parallel microchannels is studied numerically by solving the equations governing conservation of mass, momentum and energy in the liquid and vapor phases. The liquid-vapor interface is tracked by a level set method which is modified to include the effects of phase change at the interface and contact angle at the wall. Also, the reversible flow observed during flow boiling in parallel microchannels has been investigated. Based on the numerical results, the effects of contact angle, wall superheat and the number of channels on the bubble growth and reversible flow are quantified.