• Wind and Structures
• /
• v.9 no.2
• /
• pp.95-108
• /
• 2006

Wind turbines are highly complex structures for numerical flow simulation. They normally comprise of a turbine mounted on a tower thus the movement of the turbine blades and the blade/tower interaction must be captured. In addition the ground effect should also be included. There are many more important features of wind turbines and it is difficult to include all of them. A simplified set of features is chosen here for both the turbine and the tower to show how the method can begin to identify the main points connected with wind turbine wake generation and tip vortex tower interaction. An approach to modelling the rotating blades of a turbine is proposed here. The model uses point forces based on blade element theory to model the blades and takes into account their time dependent motion. This means that local instantaneous velocities can be used as a basis for the blade element theory. The model is incorporated into a large eddy simulation code and, although many important features are left out of the model, the velocity/power performance relation is generally of the correct order of magnitude. Suggested improvements to the method are discussed.

• Journal of Information Technology Services
• /
• v.8 no.1
• /
• pp.203-215
• /
• 2009

This paper illustrates the application of co-occurrence theory to generate lightweight ontologies semi-automatically. The proposed model includes three steps of a (Semi-) Automatic creation of Ontology; (they are conceptually named as) the Syntactic-based Ontology, the Semantic-based Ontology and the Ontology Refinement. Each of these three steps are designed to interactively work together, so as to generate Lightweight Ontologies. The Syntactic-based Ontology step includes generating Association words using co-occurrence in web documents. The Semantic-based Ontology step includes the Alignment large Association words with small Ontology, through the process of semantic relations by contextual terms. Finally, the Ontology Refinement step includes the domain expert to refine the lightweight Ontologies. We also conducted a case study to generate lightweight ontologies in specific domains(news domain). In this paper, we found two directions including (1) employment co-occurrence theory to generate Syntactic-based Ontology automatically and (2) Alignment large Association words with small Ontology to generate lightweight ontologies semi-automatically. So far as the design and the generation of big Ontology is concerned, the proposed research will offer useful implications to the researchers and practitioners so as to improve the research level to the commercial use.

• KIEE International Transactions on Power Engineering
• /
• v.5A no.1
• /
• pp.85-92
• /
• 2005

In this paper, Nash equilibriums of generation markets are investigated using a game theory application for simplified competitive electricity markets. We analyze the characteristics of equilibrium states in N-company spot markets modeled by uniform pricing auctions and propose a new method for obtaining Nash equilibriums of the auction. We assume that spot markets are operated as uniform pricing auctions and that each generation company submits its bids into the auction in the form of a seal-bid. Depending on the bids of generation companies, market demands are allocated to each company accordingly. The uniform pricing auction in this analysis can be formulated as a non-cooperative and static game in which generation companies correspond to players of the game. The coefficient of the bidding function of company-n is the strategy of player-n (company-n) and the payoff of player-n is defined as its profit from the uniform price auction. The solution of this game can be obtained using the concept of the non-cooperative equilibrium originating from the Nash idea. Based on the so called residual demand curve, we can derive the best response function of each generation company in the uniform pricing auction with N companies, analytically. Finally, we present an efficient means to obtain all the possible equilibrium set pairs and to examine their feasibilities as Nash equilibriums. A simple numerical example with three generation companies is demonstrated to illustrate the basic idea of the proposed methodology. From this, we can see the applicability of the proposed method to the real-world problem, even though further future analysis is required.

• Bulletin of the Korean Space Science Society
• /
• 2009.10a
• /
• pp.43.2-43.2
• /
• 2009

Electron microbursts are the intense electron precipitation which durations are less than one second. We measured the energy spectra of the microbursts from 170 keV to 340 keV with solid state detectors aboard the low-altitude (680km), polar-orbiting Korean STSAT-1 (Science and Technology SATellite). The data showed that the loss cone at these energies is empty except when microbursts abruptly appear and fill the loss cone in less than 50 msec. This fast loss cone filling requires pitch angle diffusion coefficients larger than ~ 10-2rad2/sec, while ~10-5 rad2/sec was proposed by a wave particle interaction theory. We recalculated the diffusion coefficient, and reviewed of electron microburst generation mechanism with test particle simulations. This simulation successfully explained how chorus waves make pitch angle diffusion within such short period. From considering the resonance condition between wave and electrons, we also showed ~ 100 keV electrons could be easily aligned to the magnetic field, while ~ 1MeV electrons filled loss cone partially. This consideration explained why precipitating microbursts have lower e-folding energy than that of quasi-trapped electrons, and supports the theory that relativistic electron microbursts that have been observed by satellite in-situ measurement have same origin with ~100 keV electron microbursts that have been usually observed by balloon experiments.

• Journal of Intelligence and Information Systems
• /
• v.29 no.4
• /
• pp.111-127
• /
• 2023

This study is a study on user perception of ChatGPT use. The goal of this study is to analyze the relationship between user policy expectations and user innovativeness on ChatGPT technology acceptance and intention to use using variables of TRA (Theory of Reasoned Action). The impact of policy expectations and user innovativeness on the intention to use by mediating usefulness and hedonic motivation, and the impact of subjective norms on the usefulness and intention to use were analyzed by dividing them into the MZ generation and the non-MZ generation. It was verified whether there was a moderating effect on the effect of age differences on usefulness by interacting with policy expectations. An online survey was conducted on 300 ChatGPT users using PLS (Partial Least Square) structural equations and SPSS Package, and statistical analysis was performed using PLS and SPSS. According to the analysis results, it was confirmed that the higher the initial user's innovativeness, the higher the intention to use ChatGPT. In addition, the moderating effect analysis comparing the differences between the MZ generation and the non-MZ generation showed that policy expectations had a negative effect on the usefulness of ChatGPT use.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.2
• /
• pp.43-51
• /
• 2004

In this paper, the element combination algorithm for designing an arbitrary type of the automatic transmissions is proposed. The powertrain simulation software using this algorithm is then developed. The deliveries of the angular velocities and torques are only considered for the motion characteristics of the automatic transmissions. The effects of the vibration and noise are not considered. The automatic transmission is defined by the basic elements, i.e., planetary gear set, clutch, brake, shaft, general gear, and inertia. The transmission system is defined by the combination of these elements. The element combination matrices automatically generate the equations of motion for each shift. The self error-correcting algorithm is also developed to verify the element combination algorithm. This automotive powertrain simulation/design software with user-friendly graphic user interface has two main modules. The first module, the automatic powerflow generation module, mainly consists of the automatic powerflow and component generation algorithms. This paper covers the theory and application for the first module. The second module deals with the automatic system generation algorithm and will be discussed in the second paper.

• The Korean Journal of Food & Health Convergence
• /
• v.10 no.4
• /
• pp.1-8
• /
• 2024

This study investigates the impact of servicescape elements in franchise fast food restaurants on the attitudes and revisit intentions of Generation MZ. Employing a mixed-methods approach, we surveyed 231 MZ consumers across five major urban centers. Our findings reveal that ambient conditions, spatial layout, and technology integration significantly influence MZ consumers' perceptions and behaviors. Specifically, sustainability-oriented design, customizable spaces, and seamless digital integration emerged as key drivers of positive attitudes and increased revisit intentions. Furthermore, we identify important generational differences, with Gen Z placing higher importance on Instagram-worthy aesthetics and contactless service options compared to Millennials. This research contributes to servicescape theory by proposing a novel framework tailored to MZ consumers in the fast food context. It offers practical implications for franchise operators seeking to attract and retain this crucial demographic. Our study highlights the evolving preferences of younger consumers and underscores the need for adaptable servicescape strategies in the fast food industry. The results suggest that franchises investing in environmentally conscious designs, flexible spaces, and cutting-edge technology are likely to see improved customer satisfaction and loyalty among MZ consumers. Future research could explore the long-term effects of these servicescape elements on brand perception and market share within the competitive fast food landscape.

• Proceedings of the Korea Society of Information Technology Applications Conference
• /
• 2005.11a
• /
• pp.339-342
• /
• 2005

In order to support ultrawide-band signal generation for low rate WPAN, several types of signal generation mechanisms are suggested such as Chaos, Impluse, and Chirp signals by the activity of IEEE 802.15.4a. The communication system applied chaos theory may have ultrawide-band characteristics with spread spectrum and immunity from multipath effect. In order to use the advantage of chaotic signal generation, we introduce the system implementation of communication and networking systems with the chaos UWB signal. This system may be composed of mainly three parts in hardware architecture : RF transmission with chaotic signal generation, signal receiver using amplifiers and filters, and 8051 & FPGA unit. The most difficult part is to implement the chaotic signal generator and build transceiver with it. The implementation of the system is devidced into two parts i.e. RF blocks and digital blocks with amplifiers, filters, ADC, 8051 processor, and FPGA. In this paper, we introduce the system block diagram for chaotic communications. Mainly the RF block is important for the system to have good performance based on the chaotic signal generator. And the main control board functions for controlling RF blocks, processing Tx and Rx data, and networking in MAC layer.

• Structural Engineering and Mechanics
• /
• v.22 no.2
• /
• pp.185-195
• /
• 2006

Nowadays it is very necessary to generate artificial accelerograms because of lack of adequate earthquake records and vast usage of time-history dynamic analysis to calculate responses of structures. According to the lack of natural records, the best choice is to use proper artificial earthquake records for the specified design zone. These records should be generated in a way that would contain seismic properties of a vast area and therefore could be applied as design records. The main objective of this paper is to present a new method based on wavelet theory to generate more artificial earthquake records, which are compatible with target spectrum. Wavelets are able to decompose time series to several levels that each level covers a specific range of frequencies. If an accelerogram is transformed by Fourier transform to frequency domain, then wavelets are considered as a transform in time-scale domain which frequency has been changed to scale in the recent domain. Since wavelet theory separates each signal, it is able to generate so many artificial records having the same target spectrum.

• Advances in nano research
• /
• v.6 no.1
• /
• pp.21-37
• /
• 2018

In the present article, wave dispersion behavior of a temperature-dependent functionally graded (FG) nanobeam undergoing rotation subjected to thermal loading is investigated according to nonlocal strain gradient theory, in which the stress numerates for both nonlocal stress field and the strain gradient stress field. The small size effects are taken into account by using the nonlocal strain gradient theory which contains two scale parameters. Mori-Tanaka distribution model is considered to express the gradually variation of material properties across the thickness. The governing equations are derived as a function of axial force due to centrifugal stiffening and displacements by applying Hamilton's principle according to Euler-Bernoulli beam theory. By applying an analytical solution, the dispersion relations of rotating FG nanobeam are obtained by solving an eigenvalue problem. Obviously, numerical results indicate that various parameters such as angular velocity, gradient index, temperature change, wave number and nonlocality parameter have significant influences on the wave characteristics of rotating FG nanobeams. Hence, the results of this research can provide useful information for the next generation studies and accurate deigns of nanomachines including nanoscale molecular bearings and nanogears, etc.