• Communications of Mathematical Education
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• v.24 no.3
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• pp.627-658
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• 2010

The introduce and accurate understanding of the concept of tangent line is very important in Mathematics education and its applications. In this study, we investigated the introduction method in the textbook for tangent line and its concepts. And we studied the effective teaching methods for the accurate understanding using Lakatos learning theory, GSP and related precedence studies. Finally we suggest the teaching plan for the equation of for the tangent line in the high school and apply to the High school students.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.3 s.246
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• pp.295-301
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• 2006

The wheel slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional ABS systems. In order to achieve the superior braking performance through the wheel-slip control, real-time information such as the tire braking force at each wheel is required. In addition, the optimal target slip values need to be determined depending on the braking objectives such as minimum braking distance, stability enhancement, etc. In this paper, a robust wheel slip controller is developed based on the adaptive sliding mode control method and an optimal target slip assignment algorithm. An adaptive law is formulated to estimate the longitudinal braking force in real-time. The wheel slip controller is designed using the Lyapunov stability theory and considering the error bounds in estimating the braking force and the brake disk-pad friction coefficient. The target slip assignment algorithm is developed for the maximum braking force and searches the optimal target slip value based on the estimated braking force. The performance of the proposed wheel-slip control system is verified In simulations and demonstrates the effectiveness of the wheel slip control in various road conditions.

• The Journal of Information Systems
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• v.32 no.2
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• pp.63-85
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• 2023

Purpose According to a recent survey, more than 90% of customers make purchase or use decisions for their products and services, primarily based on word-of-mouth(WOM) information (reviews, recommendations, ratings, etc.). However, few studies have explored what factors influence user's WOM intention in the context of OTT service. To address this gap, this study investigates the antecedent factors of WOM intention by adopting stimulus-organism-response (SOR) theory and pleasure arousal dominance (PAD) theory as a theoretical basis. Design/methodology/approach The research model consists of stimulus factors (diversity of original content, aesthetics, interactivity, personalization quality), emotional factors (pleasure, excitement, dominance), and behavioral factor (WOM intention). The research hypothesis was tested using the survey data collected from OTT service users of 305. Findings The result reveals that diversity of original content significantly affects on pleasure and arousal whereas it is not associated with dominance. Findings indicate that aesthetics positively influences pleasure, and interactivity is not associated with arousal. It is also proven that personalization quality has a positive effect on dominance. In addition, pleasure, arousal, and domination are proven to be positively and significantly related to WOM intention.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.331-333
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• 2004

In this study, we implement the multiple frequency bioelectrical impedance analysis system for body composition analysis. Overall system consists of : 1) conductivity electrodes to contact with hands and foots, 2) multiple frequency alternating current signal generator for generating 5, 50, 250kHz frequency and 800uA contained alternating current signal, 3) voltage signal detector, 4) phase signal detector, 5) key-pad to input individual information, 6) micro controller for data processing, 7) LCD for processed data to display, 8) system power, We explain the architecture of the system and required theory to implement the system. Finally, experimental results are illustrated to show the performance of the system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.207-210
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• 2003

The chemical mechanical planarization (CMP) process is a method of planarizing semiconductor wafers with a high degree of success. However, fundamental mechanisms of the process are not fully understood. Several theoretical analyses have been introduced, which are focused on kinematics, von Mises stress distributions and hydrodynamic lubrication aspects. This paper is concerned with hydrodynamic lubrication theory as the chemical mechanical planarization model; the three-dimensional Reynolds equation is applied to predict slurry film thickness and pressure distributions between the pad and the wafer. This paper classifies geometry of wafer into 3 types and focuses on the differences between them.

• Journal of KSNVE
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• v.5 no.2
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• pp.235-246
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• 1995

Experiment on the modal balancing of a flexible rotor supported on two kinds of fluid film bearings is performed to verify the modal balancing theory. The fluid film bearings are a tilting pad bearing and a two axial grooved journal bearing. One is inherently stable, but the other is not. The experimental result shows that the modal balancing method is effective for balancing of a high speed flexible rotor system. Besides, the critical speeds and mode shapes measured experimentally are in good coincidence with the results of rotordynamic analysis. Oil whip, which is the instability phenomenon due to fluid film force, is also observed during the experiment.

• International journal of advanced smart convergence
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• v.13 no.1
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• pp.57-68
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• 2024

In this paper, we are interested in how creator economy startups allowing creators to make money from doing that they love. So, we look at European creator economy startups among Web3.0 business model landscape surveyed in 2022, because the US is home of Web2.0 giant platforms like YouTube. Totally seventeen European startups are investigated, and the theoretical logic is the disruptive innovation. We firstly review the survey published in 2022 and utilize the theory of the disruptive innovation to design the research framework including questions with each type of the disruptive innovation. In this paper, we firstly show, Kalao and Gem as NFT ecosystem platforms aim at service convenience. Secondly, Talkbase, Passionfroot, Bildr, Customuse, and Earnr aim at providing creator tools for under-skilled customers. Lastly, when it comes direct monetization with a decentralized business model, CrowdPad, Admix, GOALS, Realm, Dropstar, Pianity, Sonomo, Stage11, Miiji, and ReadyPlayerMe are representative. Despite the relatively small data size, the results are meaningful as they contribute to a more profound comprehension of the Web3.0 business models and offer guidance for future research directions.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.3 s.96
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• pp.251-258
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• 2005

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings (HDB) in an HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Reynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigen value problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.572-578
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• 2003

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings in a HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Raynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigenvalue problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• International Journal of Automotive Technology
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• v.8 no.2
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• pp.211-217
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• 2007

The wheel slip control systems are able to control the braking force more accurately and can be adapted to different vehicles more easily than conventional ABS (Anti-lock Brake System) systems. In realizing the wheel slip control systems, real-time information such as the tire braking force at each wheel is required. In addition, the optimal target slip values need to be determined depending on the braking objectives such as minimum braking distance and stability enhancement. In this paper, a robust wheel slip controller is developed based on the adaptive sliding mode control method and an optimal target slip assignment algorithm is proposed for maximizing the braking force. An adaptive law is formulated to estimate the braking force in real-time. The wheel slip controller is designed based on the Lyapunov stability theory considering the error bounds in estimating the braking force and the brake disk-pad friction coefficient. The target slip assignment algorithm searches for the optimal target slip value based on the estimated braking force. The performance of the proposed wheel slip control system is verified in HILS (Hardware-In-the-Loop Simulator) experiments and demonstrates the effectiveness of the wheel slip control in various road conditions.