• Journal of Aerospace System Engineering
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• v.4 no.2
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• pp.1-9
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• 2010

An airless tire has advantages over the conventional pneumatic tire in terms of flat proof and maintenance free. According to the recently disclosed inventions on the airless tire, non-pneumatic tire (NPT) consists of the flexible polygon spokes. Considering the NPT structure, the spokes undergo the tension-compression cyclic loading while the tire rolls. Therefore the spokes of NPT are required to have both stiffness and resilience under the cyclic tensile-compressible loading. In general, if a material has a high stiffness, it shows a low elastic strain limit. In this paper, using the auxetic honeycomb structure with negative poissons's ratio, the spokes of NPT tire are designed to have both stiffness and resilience. Finite element based numerical simulation of the contact pressure of a NPT is carried out with ABAQUS.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.8
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• pp.719-724
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• 2011

A Non_Pneumatic tire (NPT) has spoke to replace air of the pneumatic tires. A NPT appears to have advantages over the conventional pneumatic tire in terms of flat proof and maintenance free. And a NPT can also be used in the space environment since it uses no air for inflation. In this study, the static contact pressure of NPTs with auxetic honeycomb spokes is investigated as a function of vertical loading and is compared with that of a pneumatic tire. The finite element based numerical simulation of the local stress of an airless tire is carried out with ABAQUS for varying vertical force and honeycomb spokes geometries.

• Maritime Security
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• v.7 no.1
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• pp.1-29
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• 2023

For the last 70 years, the U.S.-led bilateral security system, or "Hub-and-Spokes" system, has been applied to Northeast Asia, and the system has been successfully settled in terms of stability and economic achievements of the region. Given the increasing complexity of the security environment of East Asia, it is plausible to consider the possibility of a security system shift from bilateral alliances to collective security. In order to analyze the driver of collective security system, this study developed three factors of formation and development of collective security system - main threat, intensity of the threat, and confidence among countries in the system - by reviewing international political theories related to security cooperation. Comparing the formation, development, and achievements of NATO and SEATO, the study figures out that the existence of the main threat, the high intensity of the threat, and the strong confidence among countries in the security system are the primary drivers for a successful collective security system. Based on the result, the study also analyzed the possibility of a security system shift in East Asia. Considering contemporary international conflicts such as U.S.-China strategic competition, Russia-Ukraine War, and growing threats posed by North Korean nuclear and missiles, the study anticipates that the necessity of a collective security system that will replace the current security system of the region would arise. Still, although some issues between countries should be overcome, the growing intensity of the threats will promote cooperation among countries by improving their confidence.