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Development of Actuation System forWearable Robots using Spiral Spring
Yongtae Kim,Changyong Song,Jaeheung Park 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10
Wearable robots, or exoskeleton robots, are getting great attention because of the increasing need for seniors, disabled people, and workers in extreme environments. One of the most important requirements of the exoskeleton robot is preventing fatigues of these people. Although exoskeleton robots have been developed, there are still limitations on the user’s comfort and detection of his or her intention of motion. To improve on these aspects, spiral spring and sensor band are proposed to be used as actuation and sensor components in this paper. The spiral spring’s efficiency for wearable robots is investigated theoretically and the experiments using the spiral spring and sensor band are conducted. The experimental results demonstrate the proposed actuation and sensor system could improve the performance of the exoskeleton robots.
THE MULTILEVEL SECURITY PROBLEM OVER CLASS SEMIGROUPS OF IMAGINARY QUADRATIC NON-MAXIMAL ORDERS
KIM, YONGTAE 호남수학회 2006 호남수학학술지 Vol.28 No.2
A scheme based on the cryptography for enforcing multilevel security in a system where hierarchy is represented by a partially ordered set was first introduced by Akl et al. But the key generation algorithm of Akl et al. is infeasible when there is a large number of users. In 1985, MacKinnon et al. proposed a paper containing a condition which prevents cooperative attacks and optimizes the assignment in order to overcome this shortage. In 2005, Kim et al. proposed key management systems for multilevel security using one-way hash function, RSA algorithm, Poset dimension and Clifford semigroup in the context of modern cryptography. In particular, the key management system using Clifford semigroup of imaginary quadratic non-maximal orders is based on the fact that the computation of a key ideal $K_0$ from an ideal $EK_0$ seems to be difficult unless E is equivalent to O. We, in this paper, show that computing preimages under the bonding homomorphism is not difficult, and that the multilevel cryptosystem based on the Clifford semigroup is insecure and improper to the key management system.
Samuel Johnson as a Moralist in "The Vanity of Human Wishes," The Rambler, and Rasselas.
Kim, Yongtae 한국현대영미어문학회 2001 The Journal of KACELLS Vol.6 No.2
Dealing with a series of his writings written from his late thirties to late forties, such as "The Vanity of Human Wishes," The Rambler, and Rasselas, this article sets out its argument with a premise that through these writings Samuel Johnson carries out experiments on moral problems. A crucial source of moral problems will be drawn from the phrase of "hunger of imagination" mentioned by Imlac in his visitation to the Pyramids in Rasselas and considered to be the root from which any other moral evils branched forth. Johnson's understanding of imagination has two sides: positive and negative. In its positive sense he praises man's capacity to create something special through his industrious working of imagination. Yet, it is the very negative side of imagination that I am going to examine in this article. He offers his negative view on imagination emphasizing the preying capacity of human imagination. The nature of preying imagination is that whatever we have we are always to imagine more; to imagine more leads to wanting more; and finally wanting more brings about fatal loss. Unchecked imagination is bound to give rise to other negative faculties of human mind: pride and wishing for fame delude us into thinking that we are standing over other people in terms of wealth, learning or political power, and, consequently, pride arouses envy and hostility among the opponents. Seeing that those moral problems are mainly caused by man's detachment from outside realities, therefore, Johnson suggests as an effective therapy the genuine contact with the variety of realities.
Yongtae Kim,Seunggyu Lee,Jongchul Kim,Seunghwa Ryu 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.77 No.3
In order to reduce enormous cost of real-scale underwater explosion experiments on ships, the mechanical response of the ships have been analyzed by combining scaled-down experiments and Hopkinson’s scaling law. However, the Hopkinson’s scaling law is applicable only if all variables vary in an identical ratio; for example, thickness of ship, size of explosive, and distance between the explosive and the ship should vary with same ratio. Unfortunately, it is infeasible to meet such uniform scaling requirement because of environmental conditions and limitations in manufacturing scaled model systems. For the facile application of the scaling analysis, we propose a generalized scaling law that is applicable for non-uniform scaling cases in which different parts of the experiments are scaled in different ratios compared to the real-scale experiments. In order to establish such a generalized scaling law, we conducted a parametric study based on numerical simulations, and validated it with experiments and simulations. This study confirms that the initial peak value of response variables in a real-scale experiment can be predicted even when we perform a scaled experiment composed of different scaling ratios for each experimental variable.