• Journal of the Korean Operations Research and Management Science Society
• /
• v.36 no.3
• /
• pp.45-59
• /
• 2011

OFDMA systems have been expected to be widely used to provide multimedia services over wireless channels. To evaluate performance of the OFDMA system, power should be considered as system resource as well as subcarriers. This study propose a queueing traffic model incorporating two kinds of resources (power and subcarriers), and an extended model giving a priority to handoff calls over new calls. Some extensive experiments are conducted to illustrate the usefulness of the proposed traffic model.

• The Journal of Information Systems
• /
• v.15 no.3
• /
• pp.1-34
• /
• 2006

The purpose of this study Is to develop empirically validated instrument for business model. The previous researches related to business model were almost taxonomies. And the focus of those researches were the classification by the degree of integration and innovation the origin, and the main source of revenue etc. In the emerging fields such as IT, e-commerce, and e-business, it tends to overlook methodological issue in its substantive relationships and also measurement. Business model is taken an interest in recent years. However, as the non-establishment of construct on business model has made no empirical study, this, study tries to develop an empirical validated instrument that identifies the dimensions of business model by uncovering meaningful group or categories. For this, the outlined domain of business model are defined as an organizational level that competes in the industry through the literature reviews. And the traits such as process integration, value chain reconstruction, strategic alliance with another business model, specialty in a certain wet sustainability of essential capabilities, differentiation, convertibility, customer orientation, revenue stream, newness, innovation leadership: and vision sharing are identified in those respective domains, and then the traits are classified into five dimensions such as interlinkageableness, valueness, functionalness, preemptiveness, and goalness by their characteristics. Generating items are continued on the basis of operationalization. Confirmatory factor analysis is performed in order to develop validated instrument with LISREL measurement model. Finally the instrument is developed through the previous procedure. The implication of this study is the first empirical effort to assess business model. The resulting instrument can be used with dependent variables in the future study related to business model. And the establishment of construct of business model is able to make a basis to rise an additional issue consequently. In the practical side, the instrument also can be employed as an assessment framework that can assess whether the expected value success or not. The instrument with the measurement can be used on competitor's business model, In. When an investment into a i-m with a specific business model, these instrument developed can be presented as the basic framework of assessment.

• Journal of Information Technology Applications and Management
• /
• v.25 no.4
• /
• pp.157-169
• /
• 2018

The purpose of this study was to examine the volatility of bitcoin, diagnose if bitcoin are a systematic risk asset, and evaluate their effectiveness by estimating market beta representing systematic risk using GARCH (Generalized Auto Regressive Conditional Heteroskedastieity) model. First, the empirical results showed that the market beta of Bitcoin using the OLS model was estimated at 0.7745. Second, using GARCH (1, 2) model, the market beta of Bitcoin was estimated to be significant, and the effects of ARCH and GARCH were found to be significant over time, resulting in conditional volatility. Third, the estimated market beta of the GARCH (1, 2), AR (1)-GARCH (1), and MA (1)-GARCH (1, 2) models were also less than 1 at 0.8819, 0.8835, and 0.8775 respectively, showing that there is no systematic risk. Finally, in terms of efficiency, GARCH model was more efficient because the standard error of a market beta was less than that of the OLS model. Among the GARCH models, the MA (1)-GARCH (1, 2) model considering non-simultaneous transactions was estimated to be the most appropriate model.

• Journal of the Korea Convergence Society
• /
• v.11 no.6
• /
• pp.209-213
• /
• 2020

In this study, the model A with the existing shape used at racing car and the model B with light weight were designed. The structural analysis with thermal deformation and stress were carried out. Model A shows that the maximum temperature is lower than model B. The cooling performance due to the shape of the disk without any other cooling conditions can be shown to be better for model A. Model A was seen to be superior in durability as the thermal stress reduced by almost twice as much as model B. The part where the greatest stress occurred appeared to be the hole jointed with the hub regardless of its shape. The analysis results at this study are seen to be useful at designing the shape of the actual vehicle brake disc. The analysis results obtained in this study can be applied at grasping the strength of the brake disk for racing car practically. By utilizing the analysis result of the brake disk for racing car, this study is seen as the convergence study that the aesthetic design and analysis are applied.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.104-108
• /
• 2003

Finite element (FE) model updating is a procedure to minimize the differences between analytical and experimental results, which can be usually posed as an optimization problem. This paper aims to introduce a hybrid optimization algorithm (GA-SA), which consists of a Genetic algorithm (GA) stage and an Adaptive Simulated Annealing (ASA) stage, to FE model updating for a shrunk shaft. A good agreement of the first four natural frequencies has been achieved obtained from GASA based updated model (FEgasa) and experiment. In order to prove the validity of GA-SA, comparisons of natural frequencies obtained from the initial FE model (FEinit), GA based updated model (FEga) and ASA based updated model (FEasa) are carried out. Simultaneously, the FRF comparisons obtained from different FE models and experiment are also shown. It is concluded that the GA, ASA, GA-SA are powerful optimization techniques which can be successfully applied to FE model updating, the natural frequencies and FRF obtained from all the updated models show much better agreement with experiment than that obtained from FEinit model. However, FEgasa is proved to be the most reasonable FE model, and also FEasa model is better than FEga model.

• Journal of Korean Port Research
• /
• v.12 no.1
• /
• pp.1-8
• /
• 1998

If a system has a large boundary and complexity, forecast's accuracy will be very low when consider the system's substance as black box. Thus, it is necessary that analysis by structure model. To examine competition in Northeast Asia Ports, it has assumed that the form of structure model, For which the System Dynamics method is adapted in this paper. Northeast Asia Ports Model includes five ports - Pusan, Kobe, Yokohama, Kaoshiung, Keelung, - which are adjacent to each other by geographically and has a competition relation. The Northeast Asia Ports Model has several sub-systems which consists of each unit port models. And, each unit port model found by quantitive, qualititive factors and their feedback loops. All effects which components of one port have influence to components of the rest ports must be surveyed in order to construct Northeast Asia Ports Model, but it may be impossible currently. In this paper Northeast Asia Ports Model was simplified by HFP-Hierarchical Fuzzy Process Method-adapted to integration of level variables of unit port model. Container cargo volumes in Northeast Ports Model is distributed by results of HFP method. And distributed container cargo volumes effected to unit port model. Developed model can estimate change of container cargo volumes in competitive relation by alternation of simple parameter, and reflects dynamics characteristics which are included in model.

• Journal of Environmental Science International
• /
• v.6 no.6
• /
• pp.645-658
• /
• 1997

A study on ventilation design using the spreadsheet model is carried out to propose means of available design. A sample of complex ventilation system In the non-standard condition Is used to illustrate thins spreadsheet model. In developing the spreadsheet model, this study has attempted to it general by using computional equations and design parameters that can be readily applied to any spreadsheet software. Also, most design data is contained in the spreadsheet template. This template provides the same design information as the ACGIH worksheet, and operates Quickly and emclenuy, and is fiexible enough to use under different conditions. This spreadsheet model allows the ventilation engineer to design quickly and accurately the ventilation system, without spending too much effort In the design process. By storing on computer and diskette, the design data computed finally can be used as a permanent record of specific ventilation system, and because of finally to be able to design over and over again while making only slight changes to the Input data, the spreadsheet model is used availably to accomplish the design optimazation by redesign and troubleshooting by review from field measurements. Also, the spreadsheet model is available for designing ventilation system under different condition or evaluating existing system or design drawing, because changes In the layout or formulae can be readily made to fit the needs of the designer.

• Structural Engineering and Mechanics
• /
• v.52 no.2
• /
• pp.261-274
• /
• 2014

An accurate finite element (FE) model of a structure is essential for predicting reliably its dynamic characteristics. Such a model is used to predict the effects of structural modifications for dynamic design of the structure. These modifications may be imposed by design alterations for operating reasons. Most of the model updating techniques neglect damping and so these updated models can't be used for accurate prediction of vibration amplitudes. This paper deals with the basic formulation of damped finite element model updating method and its use for structural dynamic modifications. In this damped damped finite element model updating method, damping matrices are updated along with mass and stiffness matrices. The damping matrices are updated by updating the damping coefficients. A case involving actual measured data for the case of F-shaped test structure, which resembles the skeleton of a drilling machine is used to evaluate the effectiveness of damped FE model updating method for accurate prediction of the vibration levels and thus its use for structural dynamic modifications. It can be concluded from the study that damped updated FE model updating can be used for structural dynamic modifications with confidence.

• Journal of The Korean Digital Architecture Interior Association
• /
• v.12 no.2
• /
• pp.61-66
• /
• 2012

In space syntax, the mathmatical process to get a integration could be restrictive in understanding spatial configuration since it is based on only one behavior model. In this study, As another approach to spatial configuration analysis based on behavioral model, there is the simulation tracking analysis model that simulates the movements of human in the space and analyze them. In this study, the relationship between integration and behavioral model will be defined and the similarities and the differences between space syntax and the simulation tracking analysis model will be demonstrated. Furthermore, these two analysis models will be understood as a variety of tools that can analyze an object in multiple viewpoints.

• Proceedings of the SAREK Conference
• /
• 2006.06a
• /
• pp.838-846
• /
• 2006

The purpose of this study to develop the air-conditioning system that adopts adaptive model as an indoor climate control logic for energy saving. The adaptive model using the ability of human thermal adaptation could be expected to alleviate the indoor set-point temperature compared with the past heat-balance model. Especially, in case of hybrid air-conditioning system coupled with natural ventilation and heating/cooling system, the adaptive model can be describe the thermal comfort of inhabitant who stay at hybrid system controlled buildings with accuracy. In this paper, the concept of adaptive model will be described and the results of a continuous measurement on the actual thermal experiences and behaviors of thermal adaptation for office worker will be reported.