• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.4
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• pp.759-766
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• 2015

This paper proposes a location-based key management scheme in wireless sensor networks, and among the existing location-based key management techniques, we focused on the LDK (Location Dependent Key management). In order to improve the problems occurred by communication interference, we introduced the key revision process and the method of key establishment using grid information. According to the simulation of this scheme, it increased connectivity while decreased compromise ratio than those of the previous LDK, futhermore, we confirmed that a hexagon distribution of AN reduces the network cost.

• Journal of KIISE:Information Networking
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• v.36 no.4
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• pp.263-274
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• 2009

Decentralized group key management mechanisms offer beneficial solutions to enhance the scalability and reliability of a secure multicast framework by confining the impact of a membership change in a local area. However, many of the previous decentralized solutions reveal the plaintext to the intermediate relaying proxies, or require the key distribution center to coordinate secure group communications between subgroups. In this study, we propose a decentralized group key management scheme that features a mechanism allowing a service provider to deliver the group key to valid members in a distributed manner using the proxy cryptography. In the proposed scheme, the key distribution center is eliminated while data confidentiality of the transmitted message is provided during the message delivery process. The proposed scheme can support a secure group communication in dynamic network environments where there is no trusted central controller for the whole network and the network topology changes frequently.

• Structural Engineering and Mechanics
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• v.68 no.4
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• pp.475-483
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• 2018

Square tubular columns are commonly used in moment resisting frames, while through-diaphragm connection is the most typical configuration detail to connect the H-shaped beam to the column. However, brittle fracture normally occurs at the complete joint penetration weld between the beam flange and the through-diaphragm due to the stress concentration caused by the geometrical discontinuity. Accordingly, three improved types of through-diaphragm are presented in this paper to provide smooth force flow path comparing to that of conventional connections. Tensile tests were conducted on four specimens and the results were analyzed in terms of failure modes, load-displacement response, yield and ultimate capacity, and initial stiffness. Furthermore, strain distributions on the through-diaphragm, the beam flange plate, and the column face were comprehensively evaluated and discussed. It was found that all the proposed three types of improved through-diaphragm connections were able to reduce the stress concentration in the welds between the beam flange and the through-diaphragm. Furthermore, the stress distribution in connection with longer tapered through-diaphragm was more uniform.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.688-698
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• 2016

In this paper, we investigate the achievable sum rate and energy efficiency of downlink massive multiple-input multiple-output antenna systems with zero-forcing precoding, by taking into account the randomness of user locations. Specifically, we propose two types of non-uniform user distributions, namely, center-intensive user distribution and edge-intensive user distribution. Based on these user distributions, we derive novel tight lower and upper bounds on the average sum rate. In addition, the impact of user distributions on the optimal number of users maximizing the sum rate is characterized. Moreover, by adopting a realistic power consumption model which accounts for the transmit power, circuit power and signal processing power, the energy efficiency of the system is studied. In particular, closed-form solutions for the key system parameters, such as the number of antennas and the optimal transmit signal-to-noise ratio maximizing the energy efficiency, are obtained. The findings of the paper suggest that user distribution has a significant impact on the system performance: for instance, the highest average sum rate is achieved with the center-intensive user distribution, while the lowest average sum rate is obtained with the edge-intensive user distribution. Also, more users can be served with the center-intensive user distribution.

• ETRI Journal
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• v.34 no.5
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• pp.655-665
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• 2012

Based on wideband precoding (WBP) in the multiple-input multiple-output orthogonal frequency division multiplexing system, an adaptive nonuniform codebook is presented in this paper. The relationship between the precoder distribution and spatial correlation is analyzed at first. A closed-form expression based on overlapped isosceles triangles is proposed as an approximation of the precoder distribution. Then, the adaptive codebook design is derived with the approximate distribution to minimize quantization errors. The capacity and bit error rate performance demonstrate that the adaptive codebook with WBP outperforms the conventional fixed uniform codebook.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.1 no.1
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• pp.38-46
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• 1991

This paper pro poses a ley distribution system based on identification information. The system uses an indivdual user's identification instead of the public file used in the Diffie-Hellman sustem. It does not require any services of a center to distribute work keys and users to keep directory public file. We propose an identity-based key distribution system for generating a commom secret conference kdy for two or more users. We assume users are connected in a ring network. Message among users authenticated using each user's identification informa-tion. The security of the our proposed system is based on the difficulty of both factoring large numbers and computing discrete logarithms over large finite fields.

• The Journal of Advanced Prosthodontics
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• v.14 no.1
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• pp.1-11
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• 2022

PURPOSE. The maximum width between the mesial and distal labial transitional line angles, described as "esthetic width" herein, could significantly influence the visual perception of the teeth and smile. This study aimed to conduct biometric research on esthetic width and to explore whether regular distribution exists in the esthetic width of human teeth. MATERIALS AND METHODS. A total of 4,264 maxillary and mandibular anterior teeth were measured using the Geomagic studio software program. The proportions of maxillary to mandibular homonymous teeth and proportions between the adjacent teeth were calculated. Bilateral symmetry and the correlation between the esthetic and mesiodistal widths were both accounted for during the measurement procedures. RESULTS. The mean esthetic widths were 6.773 ± 0.518 mm and 4.329 ± 0.331 mm for maxillary and mandibular central incisors, respectively, 5.451 ± 0.487 mm and 5.008 ± 0.351 mm for maxillary and mandibular lateral incisors, respectively, and 3.340 ± 0.353 mm and 5.958 ± 0.415 mm for maxillary and mandibular canines, respectively. Except for the mandibular canines, no significant difference in esthetic width was found among homonymous teeth from the same jaw. A high linear correlation was found between the esthetic and mesiodistal widths of the same tooth, except for the maxillary canines. Esthetic width proportions among different tooth categories showed some regular patterns, which were similar to those of the mesiodistal width. CONCLUSION. Esthetic width is regularly distributed among the teeth in the Chinese population. This could provide an important reference for anterior dental restorations and dimension recovery in esthetic reconstruction of anterior teeth.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.15
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• pp.6411-6414
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• 2014

Background: A dense breast not only reduces the sensitivity of mammography but also is a moderate independent risk factor for breast cancer. The percentage of Western women with fat breast tissue is higher aged 40 years or older. To a certain extent, mammography as a first choice of screening imaging method for Western women of this group is reasonable. Hitherto, the frequency and age distribution of mammographic breast density patterns among Chinese women had not been characterized. The purpose of this study was to investigate the frequency and age distribution of mammographic breast density patterns among a group of Chinese screening women and breast cancer patients in order to provide useful information for age-specific guidelines for breast cancer screening in Chinese women. Methods: A retrospective review of a total of 3,394 screening women between August and December 2009 and 2,527 breast cancer patients between July 2011 and June 2012 was conducted. Descriptive analyses were used to examine the association between age and breast density. The significance of differences of breast density between the screening women and the breast cancer patients was examined using nonparametric tests. Results: There was a significant inverse relationship between age and breast density overall (r=-0.37, p< 0.01). Breast density of the breast cancer patients in the subgroups of 40-49 years old was greater compared with that of the screening women, the same in those aged 50-54 years and in those 55 years old or older, less than in the screening group. Conclusions: With regard to the Chinese women younger than 55 years old, the diagnostic efficiency of breast cancer screening imaging examinations may be potentially improved by combining screening mammography with ultrasound.

• ETRI Journal
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• v.28 no.3
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• pp.375-378
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• 2006

This letter presents a pairwise key establishment scheme that is robust against the compromise of nodes in mobile ad hoc networks. Each node establishes local keys with its neighbor nodes that are at most three hops away at network boot-up time. When any two nodes establish a pairwise key, they receive the secret information from the nodes on the route between them, and construct the pairwise key using the secret information. Here, the local keys are utilized by the nodes on the route to send the secret information securely. The simulation results have proven that the proposed scheme provides better security than the key pre-distribution-based scheme.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.10 no.3
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• pp.69-76
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• 2000

In this paper we propose a new group key renewal scheme suitable for secure mobile communications in which all members of the group can re-share the new group common key excepted a revoked member using a key distribution center(a trusted center). A renewal group key in the proposed scheme can be shared many times using pre-distributed data by a smart card without a preparation stage. This scheme is also avaliable for a large group network because the transmitted data amount after identifying the revoked member does not depend on a size of group. The secuirty of this scheme is based on the difficulty of the discrete logarithm problem.