• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1673-1678
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• 2005

This paper addresses both theoretical and experimental studies of the stability of haptic interfaces during the simulation of virtual Coulomb friction. The first objective of this paper is to present an analysis of how friction affects stability in terms of the describing function method and the absolute stability theory. Two different feedback methods are introduced and are used to evaluate the analysis: an active force feedback, using a motor, and a passive force feedback, using controllable brake. The second objective of this paper is to present a comparison of the theoretical and experimental results. The results indicate that the sustained oscillations due to the limit cycle occur when simulating friction with an active force feedback. In contrast, a passive force feedback can simulate virtual friction without the occurrence of instability. In conclusion, a hybrid active/passive force feedback is proposed to simulate a highly realistic friction display.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.215-226
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• 2004

A dynamic reliability model which can take into account the time history of loading sequences may be applied to the analyses of the hydraulic stability of armor units on rubble-mound breakwaters. All the parameters related to the stability of structures have been considered to be constants in the deterministic model until now. Thus, it is impossible to study the effects of some uncertainties of the related random variables on the stability of structures. In this paper, the dynamic reliability model can be developed by POT(Peak Over Threshold) method in order to take into account the time history of loading sequences and to investigate the temporal behaviors of stability of structure with its loading history. Finally, it is confirmed that the results of dynamic reliability model agree with straight- forwardly those of AFDA(Approximate Full Distribution Approach) of the static reliability model for the same input conditions. In addition, the temporal behaviors of probability of failure can be studied by the dynamic reliability model developed to analyze the hydraulic stability of armor units on rubble-mound breakwaters. Therefore, the present results may be useful for the management of repair and maintenance over the whole life cycle of structure.

• Journal of Ocean Engineering and Technology
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• v.19 no.6 s.67
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• pp.64-71
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• 2005

The welding methods have been applied to the most structural products used in the automobile, ship construction, and construction. The structure steel must have sufficient strength of structure; However, the mechanical properties of the welded part changes when it is welded. Therefore, the stability or life of the structure may be affected by the changed mechanical properties. The mechanical properties of the welded part must be examined in order to ensure the safety of structure. In this research, the SS400 steel and the STS304 steel were used to estimate the mechanical properties of the HAZ by weld thermal cycle simulation. In this study, the materials were used to examine the weld thermal cycle simulation characteristic, under two conditions: the drawing with diameter of $\Phi$10 and the residual stress removal treatment. To examine the mechanical properties by the weld thermal cycle simulation, the tensile test was carried out in room temperature. The crosshead speed was lmm/min.

• Journal of the Korean Ceramic Society
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• v.45 no.3
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• pp.167-171
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• 2008

Zirconium-doped $Li_{1.1}Co_{1-x}Zr_xO_2(0{\leq}x{\leq}0.05)$ powders as cathode materials for lithium ion batteries were synthesized using an ultrasonic spray pyrolysis method. Cyclic voltammetry and cyclic stability tests were performed, and the changes of microstructure were observed. The solubility limit of zirconium into $Li_{1.1}CoO_2$ was less than 5 mol%, and monoclinic $Li_2ZrO_3$ phase was formed above the limit. The Zr-doping suppressed the grain growth and increased the lattice parameters of the hexagonal $LiCoO_2$ phase. The Zr-dopiong of 1mol% resulted in the best cyclic performance in the range of $3.0{\sim}4.3V$ at 1C rate (140 mA/g); the initial discharge capacity decreased from 158 mAh/g to 60 mAh/g in the undoped powder, while from 154 mAh/g to 135 mAh/g in the Zr-doped powder of 1 mol% after 30 cycles. The excellent cycle stability of Zr-doped powder was due to the low polarization during chargedischarge processes which resulted from the delayed collapse of the crystal structure of the active materials with Zr-doping.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.313-318
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• 2003

The vibration of washing machine at spinning cycle is important problem that affects the performance of a product. In this raper, the inner structure of the washing machine is modeled as a rigid body suspension system and transfer farce caused by rotating unbalance mass is obtained using Newton's the 2nd law. and this model is used to predict the verge of walking instability during the spinning cycle. The walk of the drum washing machine is suggested by calculating the force transmissibility between drum and the cabinet. As calculating the resultant force exerted for cabinet, the friction coefficient of the pad is suggested to avoid the walk. In addition, relation between translational slip and rotational slip is derived and method to avoid the rotational slip is introduced.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1144-1148
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• 2002

We prepared the polyaniline (Pani) film and powder by chemical polymerization and doping with different dopants and also investigated the capability of Li//polyaniline cells after assembling. The oxidation/reduction potentials and electrochemical reaction of Li//polyaniline cells were tested by cyclic voltammetry technique. The Li//Pani-HCl cells with 10% and 20% conductors show a little larger specific discharge capacities than that without conductor. The highest discharge capacity of almost 50 mAh/g at 100th cycle is also achieved. However, Li//Pani-LiPF6 with 20% conductor shows a remarkable performance of ~90 mAh/g at 100th cycle. This is feasible value for using as the positive electrode material of lithium ion secondary batteries. It is also proved that the powder type electrode of Pani is better to use than the film type one to improve the specific discharge capacity and its stability with cycle.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.4
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• pp.130-137
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• 2010

This paper analyzes the main factors affecting user selection of a small-sum electronic payment system using survey data of 396 users. Several findings emerge. First, users consider three pillars and eight factors in adopting a new system : system features(stability, security, and flexibility), transaction cost(payment commission and settlement period), and financial capability of provider(stability of financial structure, risk management capability, and funding capability). Second, the stability of the financial structure of the system provider is the most important factor to user acceptance of a new e-payment system. Users tend to consider uncertainty risk more seriously than transaction cost. This reflects the reality that electronic payment system service industry has not fully fledged yet. Third, some moderating effects exist according to payment methods and business usages. As for payment methods, speedy settlement cycle for wired/wireless phone payment, system stability for credit card and account transfer payment, and security for advance payment means are crucial factors. As for business usages, the stability of financial structure for online game content, system stability for music and video content, proxy payment commission for e-learning content, flexibility of the payment system for digital adult content, and security for public services are decisive ones.

• Proceedings of the Korea Society of Design Studies Conference
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• 2004.05a
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• pp.126-127
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• 2004

• Preventive Nutrition and Food Science
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• v.1 no.2
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• pp.190-195
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• 1996

Texture-modifying and freeze-thaw stabilizing effects of different wheat gluten and modified starches on surimi based-product were evaluated. The different incorporation manners of wheat gluten and modified wheat starch in surimi gel were also examined to evaluate their effects of textural properties on surimi gel. The addition of wheat gluten reduced the gel strength of surimi, but after freeze-thaw cycle it significantly improved freeze-thaw stability by reducing freexe-thaw expressible moisture and also by preventing rubbery texture development, Gluten-1 incorporated surimi gel showed higher functionality in forming cohesive gel determined by compressive and penetration force as wall as expressible moisture after freeze-thaw cycle. Surimi gel containing modified wheat starch showed better freeze-thaw stability that of modified potato starch. When a preblended mixture of wheat gluten and starch are incorporated into surimi gel, it made gel texture significantly softer as so in high sensory score. The compertition for moisture between gluten and starch is a main reason to show different way of textural modification.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.160-167
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• 2004

A two degree-of-freedom mathematical model is presented to investigate the friction mechanism of a disc brake system. A contact parameter is introduced to describe the coupling between the in-plane and the out-of-plane motions. The model with the contact parameter is considered under the assumption that the out-of-plane motion depends on the friction force along the in-plane motion. In order to describe the relationship between the friction force and the out-of plane motion, the dynamic friction coefficient is considered as a function of both relative velocity and normal farce. Using this friction law, a contact stiffness matrix along the normal direction can be obtained. The out-of-plane motion is then investigated by both the stability analysis and the numerical analysis for various parametric conditions. The results show that the stiffness parameters of the pad and the disc must be controlled at the same time. Also, the numerical analysis shows the existence of limit cycle caused by the effect of intermittent contact stiffness.