• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4C
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• pp.454-461
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• 2007

The next-generation computer is the ultra-lightweight mobile computer that communicates with peripheral handhold devices and provides dynamically the services appropriate to user. To provide the dynamic services on the ultra-lightweight mobile computer, security problem for user or computer system information should be solved and security mechanism is necessary for the ultra-lightweight mobile computing environment that has battery limit and low performance. In this paper, the security mechanism on the component based middleware for the ultra-lightweight mobile computer was implemented using RC-5 cipher algorithm and SHA-1 authentication algorithm. The security components are dynamically loaded and executed into the component based middleware on the ultra-lightweight mobile computer.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.7
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• pp.20-26
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• 2003

The ultra-lightweight high strength polymer concrete could be used for the drain structures under severe condition. In this study, materials used were unsaturated polyester resin, heavy calcium carbonate, artificial lightweight coarse aggregate and perlite. In the test results, the unit weight of the ultra-lightweight high strength polymer concrete was 946 kg f/$\textrm{m}^3$ and the compressive strength was appeared in 34.5 MPa. The compressive strength, splitting tensile strength, flexural strength, acid resistance and weather resistance were shown in excellently than that of the normal cement concrete. The draining trench had 1m length, 0.24 m width, 0.02 m thickness and 0.07 m height. The developed trench could be effectively used at the draining structures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1C
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• pp.24-33
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• 2012

Recently, the ultra-lightweight authentication RFID protocol that can actually implement on the RFID Tag is one among authentication protocols getting a concern, but recently many problems were clarified of the feature becase of the protocol which doesn't use the security algorithm. In this paper, we analyzed the problem of the ultra-lightweight authentication protocols and propose the design of ultra-lightweight RFID authentic ation protocols improving the index processing techniques. Because of improving the index processing technique in the method sending the Server authentication message to the authenticated tag, the proposed protocol is strong against the active attack which Li presents. Besides, the proposed protocol has the buffer storage of the keys and index and is strong against the asynchronous attack.

• Journal of the Korea Society of Computer and Information
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• v.24 no.4
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• pp.11-18
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• 2019

Previous mutual authentication schemes operate on the basis of validated cryptographic functions and hash functions, but these functions require a certain amount of memory capacity. However, since ultra-lightweight IoT devices have a very small amount of memory capacity, these functions can not be applied. In this paper, we first propose a text steganography communication scheme suitable for ultra-lightweight IoT devices with limited resources, and then propose a mutual authentication scheme based on the text steganography communication. The proposed scheme performs mutual authentication and integrity verification using very small amount of memory. For evaluation, we implemented the proposed scheme on Arduino boards and confirmed that the proposed scheme performs well the mutual authentication and the integrity verification functions.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.3
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• pp.132-139
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• 2019

EPS (expanded polystyrene) is one of the most used building materials for insulation that is favored by its excellent heat insulation, economical efficiency and lightweight characteristics. However, EPS is vulnerable to the fire and producing large amount of toxic gases in case of fire. Therefore, ultra-lightweight geopolymer which can replace EPS is fabricated by using IGCC (integrated gasification combined cycle) fused slag and Si sludge as raw materials and the possibility of replacement on ultra-lightweight geopolymer for EPS as an insulation building material was evaluated in this study. Ultra-lightweight geopolymer can be fabricated with the pulverized IGCC fused slag having low carbon content and density, compressive strength, thermal conductivity were $0.064g/cm^3$, 0.04 MPa, and 0.072 W/mK, respectively. The thermal conductivity of ultra-lightweight geopolymer is 1.5~2.0 times higher than that of EPS suggested in the KS M 3808; however, the thermal conductivity value of geopolymer is meaningful and competitive to that of EPS in the market. Therefore, ultralightweight geopolymer can be applicable to the building material for thermal insulation purpose and have an enough possibility to replace EPS in the future because it is not only much safer than EPS in case of fire but also it can be fabricate by using waste materials from the industry.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.5
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• pp.137-144
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• 2016

This paper aims to ensure describe the a spring-back prevention technique for improving shape fixability by using an ultra-high strength steel sheet with 980 MPa to develop a lightweight seat rail parts. Ultra-high strength steel gives a potential for considerable weight reduction and a cost-effective way to produce energy efficient vehicles. The influence of a spring-back of seat rail parts on the shape fixability in forming processes was investigated to be solved by an adjustment of the appropriate tool design and process parameters. The computed results for improving shape fixability were in good agreement with the experimental results.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.269-275
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• 2020

In this study, flexural tests of precast concrete panels according to the thickness of cross-sectional and the with or not of reinforcement were carried out in order to develop and assess of a lightweight precast concrete panel using ultra high performance concrete. For the test, four panels were fabricated, and consisted of one normal concrete panel and three ultra high performance concrete panels. As a test result, it was found that the plain precast panel using ultra high performance concrete had a lower flexural performance than the reinforced normal concrete panel, regardless of the cross-sectional size. The flexural performance of the hollow-sectional precast panel applying ultra high performance concrete, is improved by 150% compared to that of the reinforced normal concrete panel. That is, through additional performance verification and optimization of the cross-sectional design of the panel, the ultra high performance concrete precast panel can be made lighter. Also, the practical use of lightweight precast panels with ultra high performance concrete can be available through evaluation on shear, joint connection and anchoring, etc.

• Structural Engineering and Mechanics
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• v.81 no.5
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• pp.551-563
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• 2022

Bolted connector could be an alternative to replace the conventional welded headed stud in steel-ultra high performance concrete (UHPC) lightweight composite structures. In this paper, a novel demountable bolted shear connector, consisting of a high-strength bolt (HSB) and a specially-designed nut which is pre-embedded in a thin UHPC slab, is proposed, which may result in the quick installation and disassembly, due to the mountable, demountable and reusable features. In order to study the shear behavior of the new type of bolted shear connector, static push-out tests were conducted on five groups of the novel demountable bolted shear connector specimens and one group of conventional welded headed stud specimen for comparison. The effect of the bolt shank diameter and aspect ratio of bolt on failure mode, shear stiffness, peak slip at the steel-UHPC interface, shear strength and ductility of novel bolted connectors is investigated. Additionally, design formula for the shear strength is proposed to check the suitability for assessment of the novel demountable bolted shear connectors.

• Advances in concrete construction
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• v.15 no.6
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• pp.391-404
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• 2023

In this study, the modeling of the transverse connection of fully precast steel-UHPC (Ultra-High-Performance Concrete) lightweight composite bridges were conducted. The transverse connection between precast components plays a critical role in the overall performance and safety of the bridge. To achieve an accurate and reliable simulation of the interface behavior, the cohesive model in ABAQUS was employed, considering both bending-tension and compression-shear behaviors. The parameters of the cohesive model are obtained through interface bending and oblique shear tests on UHPC samples with different surface roughness. By validating the numerical simulation against actual joint tests, the effectiveness and accuracy of the proposed model in capturing the interface behavior of the fully precast steel-UHPC lightweight composite bridge were demonstrated.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.430-432
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• 2015

This paper describes a hardware implementation of ultra-lightweight block cipher algorithm PRESENT-80/128 that supports for two master key lengths of 80-bit and 128-bit. The PRESENT algorithm that is based on SPN (substitution and permutation network) consists of 31 round transformations. A round processing block of 64-bit data-path is used to process 31 rounds iteratively, and circuits for encryption and decryption are designed to share hardware resources. The PRESENT-80/128 crypto-processor designed in Verilog-HDL was verified using Virtex5 XC5VSX-95T FPGA and test system. The estimated throughput is about 550 Mbps with 275 MHz clock frequency.