• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.8
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• pp.2507-2528
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• 2022

Blockchain interoperability, which refers in particular to the ability to access information across blockchain systems, plays the key role for different blockchains to communicate with each other, and further supports the superstructure built on top of the cross-chain mechanism. Nowadays, blockchain interoperability technology is still in its infancy. The existing cross-chain scheme such as BTCRelay requires that the smart contract in a blockchain to download and maintain block headers of the other blockchain, which is costly in maintenance and inefficient to use. In this paper, we propose a supervision mechanism between blockchains, called Surveillant. Specially, the new entities called dual-functional nodes are introduced to commit the real-time information from the blockchain under supervision to the supervising blockchain, which enables users to have efficient cross-chain verification. Furthermore, we introduce Merkle mountain range for blocks aggregation to deal with the large-scale committing data. We propose the design of long orphan branch counter to trace the bifurcations in the blockchain under supervision. The existing incentive mechanism is improved to encourage the behaviors of dual-functional nodes. In Surveillant, the analysis and experimental results demonstrate that users are able to have efficient cross-chain verification with low maintenance overhead.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.1
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• pp.49-55
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• 2021

In this paper, an application example for fitness-for-service of material is shown. A kind of instrument valve is made of austenitic stainless steel fabricated by the cold working process. The tensile strength of the cold worked austenitic stainless steel has to be limited under 90 ksi to prevent the stress corrosion cracking in power plants. In industrial fields, tensile strengths of some materials were discovered to be over the regulation requirements in a certified material test report (CMTR). Owner's verification tests were performed to compare with that in a CMTR and to check the appropriateness. It is found that, in the case of verification test under the required test speed, valve materials could be used in the field. Although it is only one application sample of material check process in the power generation site, this case study could show an importance of basic experimental technology in academia and research circles.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.127-131
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• 2000

The paper presents both theoretical and experimental study for dynamic instabilities of a vertical cantilevered pipe with two attached lumped masses conveying fluid. The two attached lumped masses can be considered as valves or some mechanical parts in real pipe system. Eigenvalue behaviors depending on the flow velocity are investigated for the change of positions and magnitudes of an attached lumped mass and a tip mass. In order to verify appropriaty of numerical solutions, experiments were accomplished. Theoretical predictions have a good agreement with experimental ones.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.8
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• pp.1844-1853
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• 1995

Theoretical and experimental drawing characteristics for the single circular and square drawbeads are discussed. During the blank holding process, the strain distributions of upper and lower skins of specimens, and the die reactional forces are analysed by F. E. M., and they are compared with the experimental results. The drawbead restraining forces and strain distributions for the drawn specimens by the various drawing length are also analysed and compared with the experimental results. It is concluded that the theoretical simulations and results could be very useful for the prediction of real cases.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.313-318
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• 2000

This paper was to investigate the effect of component material to cause drying shrinkage of concrete. The latin square method was used in analysis of experimental results. The experimental factor was W/C, W/A, F.M and the level was divided into four step and the be analyzed. Compressive strength was mainly dependent in W/C through 90% F-verification. Drying shrinkage was mainly dependent on W/C in warly age through the same method, but not in later age. S/A, F.M did not affect compressive strength and drying shrinkage of concrete in all age.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.6
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• pp.619-626
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• 2007

This paper presents an experimental study on deformations and force characteristics of flexible plates both in air and water. The focus is on the complicated interaction problem between the fluid and flexible structures. The displacements and forces of free oscillating plates are measured and compared with each others. The effects of several plate coefficients are investigated i.e. plate thickness, aspect ratio, plate area, plate width ratio, bending angle. For the verification of the experimental results, some of them are compared with numerical simulation and show reasonable agreements.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.2
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• pp.151-157
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• 2010

This paper presents the modelling of an MR damper system through extensive experimental studies. The hysteresis of the MR damper is modelled by using the improved Bouc-wen model. A test bed for experimental studies of measuring parameters of the MR damper is designed and implemented. Based on the experimental data, the Bouc-Wen Model is modified for the MR damper system. To check the modelling property, a vehicle suspension system is controlled using a PID controller for the verification of the MR damper model.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.307-313
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• 2011

Hyundai Rotem Company has designed and manufactured the next generation high speed EMU bodyshell (M3-car). Korean Railway Safety Law specifies the loads vehicle bodies shall be capable of withstanding, identifies what material data shall be used and presents the principles to be used for design verification by analysis. Therefore, in order to fulfill the structural requirements, Hyundai Rotem Company has carried out Finite Element Analysis (FEA) and static load test to verify whether the carbody structure has enough strength to withstand the loads specified by Korean Railway Safety Law. This research contains the results obtained by the FE analysis and static load test. The FE analysis is carried out using NX I-DEAS 6.1 and specially designed test jigs and equipment are used for the load tests.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.6
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• pp.2429-2449
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• 2018

Dynamic data possession verification is a common requirement in cloud storage systems. After the client outsources its data to the cloud, it needs to not only check the integrity of its data but also verify whether the update is executed correctly. Previous researches have proposed various schemes based on Merkle Hash Tree (MHT) and implemented some initial improvements to prevent the tree imbalance. This paper tries to take one step further: Is there still any problems remained for optimization? In this paper, we study how to raise the efficiency of data dynamics by improving the parts of query and rebalancing, using a new data structure called Rank-Based Merkle AVL Tree (RB-MAT). Furthermore, we fill the gap of verifying multiple update operations at the same time, which is the novel batch updating scheme. The experimental results show that our efficient scheme has better efficiency than those of existing methods.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.11a
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• pp.165-168
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• 2019

The advancement in technology has led to the enormous use of multimedia applications. The video/image recorded by such applications provides critical information that can be used as a visual evidence. However, owing to the adequacy in using different editing tools, it is susceptible to malicious alterations. Thus, the reliability or the integrity of the visual information should be verified before using it as an evidence. In this paper, we propose an integrity verification method for the surveillance system using randomized hashing. The integrity value of the surveillance data is generated using the randomized hashing and elliptic curve cryptography (ECC), which is used later for the validation. The experimental results obtained from the embedded accident data recorder (ADR) system shows that the proposed method is very efficient and provides a high level of security.