• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.1
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• pp.90-97
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• 2014

In this paper, we have designed the antenna for Korea SAT-5 Satellite Communication which can use Ka band in the earth station. The antenna structure consist of the the dual-offset gregorian reflector that has high gain and efficiency, the corrugated horn that has symmetric radiation patterns and low side lobe levels, the iris polarizer that make circular polarization and the OrthoMode Transducer that separate transmitting and receiving signals. The designed antenna gain is more than 45.7dBi in Tx-band which use LHCP and 42.0dBi in Rx-band which use RHCP. The co-polarized and cross-polarized radiation pattern comply with ITU-R S.580-6 and S.731-1 that are recommended by International Telecommunication Union in the geostationary satellite. The Axial ratio is less than 1.0dB in Tx-band and 1.5dB in Rx-band that meet MIL-STD-188-164A.

• Journal of the Korea Society of Computer and Information
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• v.17 no.1
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• pp.171-181
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• 2012

This paper defines the AES password algorithm used as a symmetric-key-based password algorithm, and proposes the design of parallel password algorithm to utilize the resources of multi-core processor as much as possible. The proposed parallel password algorithm was confirmed for parallel execution of password computation by allocating the password algorithm according to the number of cores, and about 30% of performance increase compared to AES password algorithm. The encryption/decryption performance of the password algorithm was confirmed through binary comparative analysis tool, which confirmed that the binary results were the same for AES password algorithm and proposed parallel password algorithm, and the decrypted binary were also the same. The parallel password algorithm for multi-core environment proposed in this paper can be applied to authentication/payment of financial service in PC, laptop, server, and mobile environment, and can be utilized in the area that required high-speed encryption operation of large-sized data.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.5
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• pp.687-697
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• 1999

A finite element analysis has been utilized to analyze stress and strain fields and design a new configuration in orthopedics and implant dentistry. Load transfer and stress analysis at implant bone interface are important factors from treatment planning to long term success. Bone configuration and quality are different according te anatomy of expecting implantation site. The purpose of this study was to compare the stress distribution in maxilla and mandible accord-ing to implant length and bone engagement types. A three dimensional axi-symmetric implant model(Nobel Biocare, Gothenburg, Sweden) with surrounding cortical and cancellous bone were designed to analyze the effects of bone engagement and implant length on stress distribution. ANSYS 5.5 finite element program was utilized as an interpreting toot. Three cases of unicortical anchorage model with 7, 10, 13 mm length and four cases of bicortical anchorage model with 5, 7, 10 and 13 mm length were compared both maxillary and mandibular single implant situation. Within the limits of study, following conclusions were drawn. 1. There is a difference in stress distribution according to cortical and cancellous bone thickness and shape. 2. Maximum stress was shown at the top of cortical bone area regardless of bone engagement types. 3. Bicortical engagement showed less stress accumulation when compared to unicortical case overall. 4. Longer the implant future length, less the stress on cortical bone area, however there is no difference in mandibular bicortical engagement case.

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.313-322
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• 2002

In this paper, proposes Kerberos certification mechanism that improve certification service of PKINIT base that announce in IETF CAT Working Ggroup. Did to certificate other realm because search position of outside realm through DNS and apply X.509 directory certification system, acquire public key from DNS server by chain (CertPath) between realms by certification and Key exchange way that provide service between realms applying X.509, DS/BNS of PKINIT base. In order to provide regional services, Certification and key exchange between realms use Kerberos' symmetric method and Session connection used Directory service to connection X.509 is designed using an asymmetric method. Excluded random number ($K_{rand}$) generation and duplex encryption progress to confirm Client. A Design of Kerberos system that have effect and simplification of certification formality that reduce Overload on communication.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1407-1417
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• 2009

We propose a e-document management system that can provide segmented page information on a document according to different levels of authority from access control environment. The proposed system creates hierarchy identifier using a one-way hash chain and therefore does not need to own key information for all users as in existing system. Also by creating group keys by compounding hash chain hierarchy identifier with randomly formed group identifier, the system can flexibly respond to dynamic changes from group member movements while at the same time resolving the problems of key formation and management in document encoding technique using symmetric key for each page. Lastly as a result of comparative analysis through an experiment with existing e-document management systems, the proposed system showed superiority in the efficiency of encoding and decoding document and the speed of encoding and decoding by the pages.

• Convergence Security Journal
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• v.16 no.7
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• pp.173-180
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• 2016

There has been a growing interest in automation of factories in the country. And, the development in this regard has been actively attempted. In particular, on the basis of the "innovation 3.0 strategy of manufacturing industry", interest in the smart of the manufacturing plant of small and medium-sized enterprises has increased rapidly. As well as policy for building smart plant, technical, seeking a strategic approach. But, in order to introduce such a smart plant or factory automation systems, manufacturing plant security with vulnerability and personal information protection problems, it should always be top priority there. Accordingly, we provide the applicable lightweight secure protocols in RFID communication. It is a wireless communication technology that is most often introduced for factory automation. Our proposed lightweight secure protocol in this study, less the number of calculations in comparison with the existing public key-based and the symmetric key encryption algorithm. And it is fast in compare with the existing protocol. Furthermore, we design that it system can support to low power consumption and small consume the memory size.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.4
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• pp.72-78
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• 2009

This paper proposes a low phase noise ring voltage controlled oscillator(VCO) with a standard $0.13{\mu}m$ CMOS process for PLL circuit using the VCO-gain-controlled Delay cell. The proposed Delay cell architecture with a active resistor using a MOS transistor. This method can reduced a VCO gain so that improve phase noise. And, Delay cell consist of Wide-Swing Cascode current mirror, Positive Latch and Symmetric load for low phase noise. The measurement results demonstrate that the phase noise is -119dBc/Hz at 1MHz offset from 1.9GHz. The VCO gain and power dissipation are 440MHz/V and 9mW, respectively.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.3
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• pp.16-22
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• 2013

A general characterization procedure based on the extraction of a 2n-port admittance matrix corresponding to n uniform coupled lines on the multi-layered substrate using the Finite-Difference Time-Domain (FDTD) technique is presented. In this paper, the frequency-dependent normal mode parameters are obtained from the 2n-port admittance matrix to analyze multi-layered asymmetric coupled line structure, which in turn provides the frequency-dependent propagation constant, effective dielectric constant, and line-mode characteristic impedances. To illustrate the technique, several practical coupled line structures on multi-layered substrate have been simulated. Especially, embedded conductor structures have been simulated. Comparisons with Spectral Domain Method are given, and their results agree well. It is shown that the FDTD based time domain characterization procedure is an excellent broadband simulation tool for the design of multiconductor coupled lines on multilayered PCBs as well as thick or thin hybrid structures.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.11
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• pp.18-26
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• 1999

Recently, various simplified simulation techniques such as firite-difference beam propagation method and non-orthogonal coupled-mode theory have proposed to analyze the optical characteristics of tapered directional couplers supported by the coupling of two propagating modes. Although these approaches are often in sufficiently accurate, they do not provide the detailed solutions encountered in the analysis of tapered guiding structures. For this purpose, we introduce and utilize a newly developed modal transmission-line theory to analyze rigorously power transfer of the directional coupler. The numerical result reveals that the propagation constants of even and odd modes converge to a single value as increasing the spacer thickness between two symmetric tapered guides. Furthermore, 97% of the power incident into a guiding channel is transmitted to the other channel at the tapered angle ${\theta}=0.1^{\circ}$, and the efficiency of power transfer decreases dramatically as increasing the angle.

• Steel and Composite Structures
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• v.21 no.3
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• pp.537-551
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• 2016

A new type of composite beam which consists of a wide flange steel shape beam and an innovative type of composite slab was introduced. The composite slab is composed of concrete slab and normal flat steel plates, which are connected by perfobond shear connectors (PBL shear connectors). This paper describes experiments of two large-scale specimens of that composite beam. Both specimens were loaded at two symmetric points for 4-point loading status, and mechanical behaviors under hogging and sagging bending moments were investigated respectively. During the experiments, the crack patterns, failure modes, failure mechanism and ultimate bending capacity of composite beam specimens were investigated, and the strains of concrete and flat steel plate as well as steel shapes were measured and recorded. As shown from the experimental results, composite actions were fully developed between the steel shape and the composite slab, this new type of composite beams was found to have good mechanical performance both under hogging and sagging bending moment with high bending capacity, substantial flexure rigidity and good ductility. It was further shown that the plane-section assumption was verified. Moreover, a design procedure including calculation methods of bending capacity of this new type of composite beam was studied and proposed based on the experimental results, and the calculation methods based on the plane-section assumption and plastic theories were also verified by comparisons of the calculated results and experimental results, which were agreed with each other.