• ETRI Journal
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• v.32 no.1
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• pp.112-119
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• 2010

We present a useful design for a free access mat which supports two frequency bands of 2.4 GHz and 5 GHz. The free access mat is a sheet-shaped waveguide which consists of a tightly coupled double-layered microstrip resonator array. It provides easy access for devices in short-range wireless communications. Interference is a common problem with conventional applications which use free space transmission. Our proposed wireless access system uses a subsidiary waveguide, the free access mat. Wireless devices are proximately coupled to the free access mat through which the coupled electromagnetic (EM) wave transmits. The arrival domain of the EM wave of an application is therefore limited to an area close to the free access mat. Wireless devices can be coupled to the free access mat at an arbitrary position without contact. We previously presented a free access mat for a single frequency band. This paper presents a free access mat for the two frequency bands of 2.4 GHz and 5 GHz. The free access mat uses a ring patch resonator array which is easily excited by typical antennas and is resistant to interference. These characteristics are demonstrated by numerical simulation and confirmed by experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7B
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• pp.455-462
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• 2007

The GTS(Guaranteed Time Slot) of IEEE802.15.4 standard, which is the contention free access mechanism, has some problems such as the limited number of deployed devices, the low channel utilization and the service confirm delay. The proposed Cyclic-CFA(Contention Free Access) scheme is a modified polling algorithm that allows a large number of devices to be served Contention Free Access without polling packets. The Cyclic-CFA scheme improves the channel utilization dramatically and also reduces service delay time.

• Journal of the Korean Society for information Management
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• v.34 no.3
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• pp.251-267
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• 2017

This study aimed to analyze open access features of 1,890 Korean scientific journals registered in the Korea Citation Index (KCI). To this end, this study classified open access features of the target scientific journals into two main aspects, free access and free redistribution. The analysis results indicated that the target scientific journals had strong free access aspects. Based on websites, 67% of the target scientific journals allowed for free access without a login process and based on free database, 48% provided free access. On the other hand, the target scientific journals had weaker free redistribution aspects compared to their free access aspects. Only 14% of them offered the CC (creative commons) license. Another finding was that there were clear differences in open access aspects by academic field. Medicine, pharmacy, natural science, agriculture, fisheries, oceanography, and engineering had stronger open access aspects than humanities, sociology, arts, physical education, and interdisciplinary science. It appears that the difference was caused by the presence or absence of organizations supporting distribution of scientific journals of the fields concerned. To narrow the gap, it is recommended that the open access governance system is established to set up open access policies for Korean scientific journals regardless of academic fields and to support them.

• The KIPS Transactions:PartC
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• v.10C no.1
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• pp.11-16
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• 2003

This paper implements Multiple User Authentication System to which the system authenticating with password only has been upgraded. The 4-staged authentication including user ID, password, smart card and access control information, etc. is used at the suggested Multiple User Authentication System. The user authentication system that this paper suggests has been developed based on SecuROS/FreeBSD with the function of access control added to FreeBSD kernel. It provides both the function to limit accost range to the system to each user and the function to check that when inputting important information the demand is the one if the system ; thus, the reliability becomes increased. In the SecuROS/FreeBSD system, MAC and RBAC are being used. So, in the case of users accessing to the system, the Information about the policies of MAC and RBAC to which users would access is used in the authentication. At the time, the access to system if permitted only when the access control information that users demanded satisfies all the access control rules which have been defined In the system.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.847-850
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• 2001

본 논문에서는 최근에 많은 관심이 증가하고 있는 보안 운영체제를 위한 접근제어에 대해 기술하고 이 접근제어를 FreeBSD 에 구현한 것에 대해 설명한다. 강제적 접근제어(MAC), 신분 기반 접근제어(DAC), 그리고 역할기반 접근제어(RBAC) 과 같은 접근제어 정책들을 안전한 FreeBSD 운영체제를 위해 접근제어 정책으로 사용하였다. MAC 과 ACL 의 구현은 POSIX1003.le 의 표준에 기준 하였고 RBAC 의 구현은 NIST의 표준을 기준으로 하였다. 강제적 접근제어는 군기관이나 정부 기관의 보안 요구사항들을 만족시켜주지만 보안관리 측면에서는 유동적이지 못한 면이 있다. 반면에 역할기반 접근제어는 상업적 접근제어 정책 요구 사항들을 만족시켜주는 정책으로 유동적이고 다양한 보안 관리 정책의 요구사항들을 만족 시켜준다.

• Journal of Communications and Networks
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• v.13 no.6
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• pp.639-654
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• 2011

In this paper, we present a channel access mechanism, referred to as the enhanced mesh coordinated channel access (eMCCA) mechanism, for IEEE 802.11s-based wireless mesh networks. The current draft of IEEE 802.11s includes an optional medium access control (MAC), denoted as MCCA, which is designed to provide collision-free and guaranteed channel access during reserved periods. However, the MCCA mechanism fails to achieve the desired goal in the presence of contending non-MCCA nodes; this is because non-MCCA nodes are not aware of MCCA reservations and have equal access opportunities during reserved periods. We first present a probabilistic analysis that reveals the extent to which the performance of MCCA may be affected by contending non-MCCA nodes. We then propose eMCCA, which allows MCCA-enabled nodes to enjoy collision-free and guaranteed channel access during reserved periods by means of prioritized and preemptive access mechanisms. Finally, we evaluate the performance of eMCCA through extensive simulations under different network scenarios. The simulation results indicate that eMCCA outperforms other mechanisms in terms of success rate, network throughput, end-to-end delay, packet-loss rate, and mesh coordinated channel access opportunity-utilization.

• 전기의세계
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• v.31 no.5
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• pp.355-360
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• 1982

In numerical computation, it is desirable to access any row or column, the main diagonal, subarrays, of a matrix without any conflict for successful parallel processing. To meet this requirement special storage scheme is used for conflict-free access of necessary data. Interconnection network, which connects processing elements and processing element memory modules, is required to execute the necessary operations. In this paper we discuss the skewing method for conflict-free, access to various bit slices and single-stage interconnection networks.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.4
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• pp.467-473
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• 2001

The internal humoral factors in the central regulation of dry feed intake during water deprivation in sheep were investigated by measurement of cerebrospinal fluid (CSF) constituents. Five animals were fed dried alfalfa chaff for 2 hours once a day. Sheep in the water deprivation treatment were deprived of water for 28 hours, while the sheep in the control treatment were given free access to water. During the first hour of the 2 hour feeding period, a rapid reduction in blood volume occured in both treatments (water deprivation and free access to water). The CSF concentrations of Na, Cl and osmolality during the second hour of the 2 hour feeding period in both treatments were greater (p<0.01) than those during the first hour. The drinking behaviors in sheep were concentrated during the second hour of the 2 hour feeding period in periods of free access to water. Water intake during feeding in periods of free access to water was 1110 ml/2 h. The levels of increase in CSF osmolality with feeding during water deprivation were greater (p<0.01) than during periods of free access to water. The changes in CSF osmolality with feeding during water deprivation produced more vigorous thirst sensations in the brain compared to during periods of free access to water. The eating rates for the first hour of the allotted 2 hour feeding period were the same under both treatments. However, the eating rates for the second hour during water deprivation periods decreased significantly (p<0.05) compared to those during periods of free access to water. The decreased eating rates for the second hour during water deprivation may be due to the vigorous thirst sensations produced in the brain. The results suggest that the increase in CSF osmolality with feeding during water deprivation acts as a thirst and satiety factor in brain mechanisms controlling feeding to decrease dry feed intake in water-deprived sheep.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.1
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• pp.147-155
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• 2003

The diffusion of internet infrastructure and a fast increase of Population to use it is becoming a base of the service that can use various information, data and digital contents which were provided through off-line physically and used. Recently, the. techniques for copy deterrence and copyright protection have been important in e-commerce because various contents in digital form can be duplicated easily. The Access Control(AC) technique that only a user having the qualifications can access and use contents normally has been studied. The Conditional Access System(CAS) used in a satellite broadcasting md Digital Right Management System(DRMS) used for contents service are representative models of current commercialized access control. The CAS and DRM can be considered as an access control technique based on the payment based type(PBT). This paper describe the access control method of payment free type(PFT) suggested in ［5］ which are independent on the payment structure. And then we suggest a new access control method of payment free type which is more efficient than the previous one.

• Journal of the Korean Dietetic Association
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• v.20 no.4
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• pp.247-256
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• 2014

This study compared the perception, necessity, and satisfaction of free school foodservice among parents of students with and without access to free school foodservice. The sample included parents of students with access to free school foodservice (FSF group, 250 parents) or paid school foodservice (PSF group, 250 parents) in Taean, Chungnam. With regard to perception of school foodservice, 30% of PSF parents responded that it is a necessary part of school education, whereas 52% of FSF parents considered it as a part of national welfare service; this difference was significant (P<0.001). In terms of positive remarks, most parents in the PSF group highlighted convenience whereas the FSF group answered that their children were penalized; this difference was significant (P<0.001). In addition, 94% of PSF parents and 96.8% of FSF parents indicated that school foodservice is necessary. In terms of the perception of the free school foodservice, more FSF parents (96.4%) than PSF parents (84.4%) answered that they knew free school foodservice well; this difference was significant (P<0.001). With regard to target recipients of the free school foodservice, most parents in the PSF group said that needy students should be selected, whereas the FSF group said that all students should be eligible; this difference was significant (P<0.001). Acceptance of free school foodservice in the FSF group (34.4%) was significantly higher than that in the PSF group (23.2%). Satisfaction with free school foodservice was 3.5 points in the FSF group, which was significantly higher than the 2.9 points in the PSF group (P<0.001). In summary, parents of students with access to free school foodservice showed more positive perception and higher satisfaction than parents of students with paid school foodservice. This study recommends that parents' suggestions be considered and further perception and responses on free school foodservice be investigated.